HDMI Fundamentals: A CEDIA White Paper Compilation · by CEDIA. Other white papers to follow include HDMI 101, installation best practices, understanding EDID, understanding and interpreting

© 2016 CEDIA

HDMI Fundamentals:A CEDIA White Paper Compilation

WHITE PAPER

Revised Edition2016

01 Introduction to HDMI 3 - 8 02 HDMI Design and Initialization Sequence 9 - 14 03 HDMI Installation Best Practices 15 - 22 04 Understanding EDID 23 - 30 05 HDMI Troubleshooting 31 - 36

TABLE OF CONTENTS

3 © 2016 CEDIA

Introduction to HDMI

WHITE PAPER

Revised Edition2016

01 Acknowledgements 5

02 Glossary of Terms 5 03 Introduction: Document of Scope 5 04 Background on HDMI 5 05 Overview of the Cable 6 06 Labeling Guidelines 6

07 Concluding Remarks 8

08 References 8

TABLE OF CONTENTS

5 © 2016 CEDIA

01 ACKNOWLEDGEMENTS

2016 Revision by David Meyer; HDMI, HDCP, HDBaseT & UHD Subject Matter Expert and CEDIA Certified Instructor.

02 GLOSSARY OF TERMS

ARCAudio Return Channel. Upstream audio from display (from inbuilt TV tuner or smart TV content) back to an A/V receiver. Formats supported are the same as for S/PDIF, including PCM and 5.1 compressed formats. There are two types of ARC: Single Mode, which uses a single wire in the HDMI cable shared with Hot Plug Detect (pin 19), and Common Mode, which operates on the optional HDMI Ethernet Channel (HEC). Although Common Mode is superior, Single mode is actually more prevalent, being why ARC typically still works on cables without HEC.

CECConsumer Electronics Control, one of the channels in an HDMI connection, is dedicated to a set of advanced control functions, collectively known as CEC. When enabled by the manufacturer, CEC functionality allows connected devices to control each other in useful ways. For instance, a single command on a remote control can be used to play a DVD or to launch other complex activities across multiple devices in a home theater system.

DDCDisplay Data Channel, one of the channels in an HDMI connection. DDC is a two-wire bus (data + clock) which is based on I2C Inter-Integrated Circuit protocol. Its bidirectional communications include EDID (Extended Display Identification Data) upstream from display to source, and also the HDCP public keys and authentication data both directions between devices.

EDIDExtended Display Identification Data, the data contained (in a small memory called EEPROM) on each DVI display or HDMI sink which contains a table of supported video formats and timings, audio formats, etc. The sink/display sends this table upstream to the source over the DDC wires in the HDMI cable as part of the handshake process, which the source reads in order to optimize the resulting output video and audio format.

HECHDMI Ethernet Channel. A twisted pair of wires (pin 19, shared with HPD, and pin 14, formerly reserved) to support 100Mbps Ethernet as well as Common mode ARC. When used in combination, this channel can be referred to as HDMI Ethernet and Audio return Channel (HEAC). HEC was introduced in 2009 with HDMI 1.4, and remains an optional feature.

Source:A device that sends an HDMI signal, such as a DVD player or Set-top box.

Sink: A device that receives an HDMI signal, such as an HDTV.

HDMI Repeater: A device that both receives and sends HDMI signals, such as an A/V receiver.

TMDS:Transition Minimized Differential Signaling, a technology for transmitting serial data at very high speeds over twisted pair copper. TMDS is a core technology used in both DVI and HDMI.

03 SCOPE STATEMENT

The objective of this document is to introduce readers to the HDMI interface. It will introduce background history of the HDMI standard, a top-level overview of the cable and cable labeling guidelines. This is the first in a series of CEDIA white papers to be published by CEDIA. Other white papers to follow include HDMI 101, installation best practices, understanding EDID, understanding and interpreting HDMI test results and troubleshooting HDMI.

04 BACKGROUND ON HDMI

Digital interfaces such as HDMI have been around since early 2002 and have changed how people look at television. DVI (Digital Visual Interface) was a precursor to HDMI and used in many computer displays. The HDMI specification was designed to improve upon DVI by using a smaller connector, adding support for audio, boasting richer colors and utilizing consumer electronic control (CEC) functions. The HDMI specification describes both the physical connection in terms of connector style and pin-outs as well as the signals it transmits.

INTRODUCTION TO HDMI

6 © 2016 CEDIA

05 OVERVIEW OF THE CABLE

A HDMI connector is shown below in Figure 1.

Fig 1: HDMI male connector pin configuration Source: Kordz Pty Ltd

The cable carries three TMDS data channels (Transition Minimized Differential Signaling – the technology that allows DVI and HDMI to send high-speed digital data), one for each Red, Green and Blue signal, or Y/Cb/Cr component video signals. TMDS data includes both video and audio information, with audio packed in ‘data island periods,’ being in the video-blanking intervals. Each channel has three separate lines for positive (+) value, negative (-) value, and a ground wire. It uses a twisted pair for electromagnetic (EM) noise reduction and each pair is wrapped in a separate shield to minimize crosstalk.

When a sink receives the +5V signal from the source, the Hot Plug Detect (HPD) signal, also +5V, is sent by the sink to indicate its presence to the source device. Hot plug detect is the first step in source device recognizing a sink has been connected. The sink can toggle the hot plug detect signal to reset the HDMI connection.

Once this cycle is complete, negotiation between source and sink over the DDC channel commences. This starts with a query to prompt the display

to respond with its EDID table. This comprises manufacturer name, model number and display capabilities such as audio formats, video resolution and timings, lip sync delays, etc. HDMI specifically uses E-EDID, the extra ‘E’ at the start of which indicates Enhanced EDID, wherein the display not only provides supported formats and timings, but what’s actually preferred based on its native resolution, etc. The source can then select the optimal output accordingly.

One key area of interoperability is the DDC channel. It not only conveys E-EDID signalling upstream from sink to source, but also carries HDCP authentication and key exchange bidirectionally between devices. There are two strategies employed to manage this traffic: one, anti-collision and arbitration protocols, and two. HDMI specifying a capacitance limit of 700pF on the DDC wires in the cable (although I2C typically only specifies up to 400pF in other applications). The higher the capacitance, the greater the latency in the signaling within, which in turn may compromise the arbitration protocols stated above. It’s like running a red traffic light. This remains one of the leading causes of interoperability conflicts in HDMI.

The Consumer Electronics Control (CEC) channel is used for sending command and control data between connected devices, allowing a user to control multiple CEC-enabled devices with one remote. Many manufacturers have come up with proprietary trade names for the CEC and are sometimes not cross- brand compatible. CEC 2.0, as part of the HDMI 2.0 specification, greatly improves things but is not yet in widespread use. It is important to note implementation of CEC is optional in devices, although wiring in the cable is mandatory.

06 LABELING GUIDELINES

All cables, according to HDMI Licensing LLC, must conform to one of the five types listed on the next page. The installer and the system designer can use these labels as a guide to procure the right cables for a job. The labels define tested capabilities and minimum performance characteristics of the cable and there is no need to rely on arcane version numbers as done in the past. HDMI adopters are no longer allowed to use version numbers in the labeling, packaging, or promotion of any product, including devices and cables.


7 © 2016 CEDIA

Products cannot make any reference to HDMI version numbers, according to HDMI Licensing LLC. With cables, all that maters is its test compliance as indicated by its labeling, and with devices, supported features must be listed. However, due diligence on the installer’s part is recommended in determining compliance of all products, particularly cables and extenders, that they buy from chosen vendor/s.

‘Standard HDMI cables’ have been tested to perform at speeds of 74.25MHz clock, or 2.23 Gbps (gigabits per second) aggregate data rate. This assures, but is not limited to, 720p/1080i video signals. High Speed Cables are tested to perform at speeds of 340 MHz pixel rate, or up to 10.2Gbps for compliant support of 1080p up to 120fps (including 60fps 3D), or UHD (4K) up to 30fps.

TIP: The MHZ number is not bandwidth, it’s the clock which runs parallel to the TMDS (where the data actually is). Bandwidth at

‘High Speed’ is actually 1.7GHz.

HDMI 2.0 was introduced in 2013 as an addendum to HDMI 1.4. Both specifications remain concurrent. HDMI 2.0 increases the maximum aggregate data rate to 18Gbps, being 600MHz pixel clock and 2.97GHz of TMDS bandwidth. This provides sufficient speed for UHD at high frame rate (HFR) up to 60fps with 8-bit RGB color, or up to 12-bit YCbCr 4:2:2, with High Dynamic Range (HDR) and Wide Color Gamut (WCG), and up to 32 channels of audio.

As these high frequencies are more vulnerable to interferences, HDMI introduced three main strategies to ensure support:

1. Slower TMDS Clock - where HDMI 1.4 operates the TMDS clock equal to the pixel rate (with 8-bit color), HDMI 2.0 slows the clock to 1/4 of this relative speed (or 1/40th data rate/channel) to alleviate RFI.

2. More powerful sink EQ - a higher gain EQ in the sink’s HDMI receiver centered at 3GHz (maximum bandwidth is 2.97GHz) empowers existing certified High Speed HDMI cables to operate at even higher speeds. Practical and length limitations still apply.

3. “Premium High Speed HDMI Cables” - this optional certification standard additionally tests cables for 18Gbps data rate support, and includes physical tests for construction and EMI/RFI shielding performance.

Standard HDMI Cable

Standard HDMI Cable-with Ethernet Cable

Standard Automotive-HDMI CABLE

High Speed HDMI CABLE

High Speed HDMI Cable with Ethernet

Premium High Speed HDMI Cable


8 © 2016 CEDIA

07 CONCLUDING REMARKS

As one can see, HDMI interface is a complex technology and has become ubiquitous in our home. It is important to recognize that challenges still exist in whole-home distributed video systems and careful design is required before installing a system. The Trademark & Logo Guidelines from HDMI Licensing LLC will allow installers to procure the right cable for a job and help in a successful system design. The next document in this series covers HDMI features, design, initialization sequence and testing process.

08 REFERENCES

1. HDMI LLC. (n.d.). HDMI - Installers - Inside an HDMI cable. Retrieved June 19th, 2010, from HDMI LLC: http://www.hdmi.org/installers/insidehdmicable.aspx

2. HDMI LLC. (n.d.). HDMI: Installers: Case Studies Retrieved June 19th, 2010, from HDMI LLC: http:// www.hdmi.org/installers/case_studies.aspx

3. HDMI LLC. (n.d.). HDMI: Trademark and logo guidelines Retrieved October 7th, 2010, from HDMI LLC: http://www.hdmi.org/manufacturer/trademark_logo_pub.aspx


9 © 2016 CEDIA

HDMI Design and Initialization Sequence

WHITE PAPER

Revised Edition2016


02 Glossary of Terms 11

03 Scope 12

04 Basic Design of HDMI 12

05 HDMI Initialization Sequence 12

06 Concluding Remarks 14

07 References 14

08 Appendix A: HDMI 1.4a Features 14

TABLE OF CONTENTS

11 © 2016 CEDIA

01 ACKNOWLEDGEMENTS



4K D-cinema format describing 4,096 pixels wide x 2,160 pixels high. 4K nomenclature included consumer 3,840 x 2,160 format in HDMI 1.4, but was more aptly called 2,160p in HDMI 2.0, and standardized as ‘UltraHD’ by the Consumer Technology Association (CTA).

Audio Return Channel (ARC) The audio return path in HDMI 1.4a allows a TV to send audio data upstream to an A/V receiver, eliminating the need for a separate SPDIF audio connection. It supports the same audio formats as an SPDIF cable, which means it does not support high-definition audio or multi-channel PCM.

CECConsumer Electronics Control. One of the channels in an HDMI connection is dedicated to a set of advanced control functions, collectively known as CEC. When enabled by the manufacturer, CEC functionality allows connected devices to control each other in useful ways. For instance, a single command on a remote control can be used to play a DVD or to launch other complex activities across multiple devices in a home theater system.

DDCDisplay Data Channel, one of the channels in an HDMI connection. DDC is a two-wire bus (data + clock) which is based on I2C Inter-Integrated Circuit protocol. Its bidirectional communications include EDID (Extended Display Identification Data) upstream from display to source, and also the HDCP public keys and authentication data both directions between devices.

EDIDExtended Display Identification Data, the data contained (in a small memory called EEPROM) on each HDMI sink which contains a table of supported video formats and timings, audio formats, etc. The sink/display sends this table upstream to the source over the DDC wires in the HDMI cable as part of the handshake process, which the source reads in order to optimize the resulting output video and audio format.

HDCPHigh-bandwidth Digital Content Protection, an encryption system developed by Intel designed to protect copyrighted audiovisual content during transmission between authorized devices.

Hot Plug Detect (HPD)A function of HDMI connectivity that allows the source device to sense when a display device has been connected to it.

SourceA device that contains an HDMI transmitter to output an HDMI signal, such as a Blu-ray player or set-top box.

SinkA device that contains an HDMI receiver to input an HDMI signal, such as an HDTV.

Repeater A device with one or more transmitters (outputs) and receivers (inputs), such as an A/V receiver.

UltraHDThe industry adopted name given to 2160p or 4K. Refers to video resolution of 3,840 pixels wide x 2,160 pixels high. Also abbreviated to UHD.

Private Key(s)The HDCP secret keys which may never be transmitted or revealed. They are only used internally by HDCP devices during authentication. With HDCP 1.x they take the form of 40, 56-bit keys. With HDCP 2.2 there is no private key in the transmitter, but there is a 1,024-bit private key in every recevier.

Public Key(s)The public keys, contained in both HDCP transmitter and receiver devices, are the public vector assigned by DCP LLC which are transmitted to the interfacing device during HDCP authentication. In HDCP 1.x they are called the Key Selection Vector (KSV), being a 40-bit value comprising 20 ones and 20 zeroes. In HDCP 2.2 the public key is a 3,072-bit value in the transmitter and 1,048-bit in the receiver for far better security.

TMDSTransition Minimized Differential Signaling. The encoding method used for the three high-speed A/V channels in HDMI.

HDMI DESIGN AND INITIALIZATION SEQUENCE

12 © 2016 CEDIA

03 SCOPE

HDMI Design and Initialization Sequence is the second document in a series of HDMI white papers published by CEDIA. The first document, Introduction to HDMI Interface, introduced HDMI standards and labeling guidelines. The objective of this document is to discuss the basic design of HDMI devices and the HDMI initial-ization sequence.

04 BASIC DESIGN OF HDMI

HDMI-compliant devices can be categorized into three types: sources, sinks and repeaters.

The source contains one or more HDMI transmitter(s), and sends the content to be displayed. Examples of sources include set-top boxes, media servers, Blu-ray disc players, and computer graphic cards.

The sink contains one or more HDMI receiver(s), or inputs, for human intelligible presentation of the content. Examples of a sink device include TVs and digital projectors.

A repeater has both HDMI inputs and outputs. It accepts content, decrypts it, then re-encrypts and finally retransmits the data. In between these actions, a repeater may perform some signal processing, such as up-converting video into a higher-resolution format or splitting out the audio portion of the signal. Examples include A/V receivers that separate and independently handle the audio signal while also retransmitting the video for display on a TV. A repeater can also transmit the protected content to multiple outputs for simultaneous display on several screens.

05 HDMI INITIALIZATION SEQUENCE

The initialization process can be categorized into three distinct units: power, low-speed and high-speed. The power stage affirms the presence of all devices. The low-speed protocols are the most critical, being identification of devices, optimization of signaling, and the handshake process to authorize the sending of encrypted data. The high-speed stage is the A/V data transmission itself, operating at up to 18Gpbs.

Power

The connection process begins when the devices are turned on and the sink detects a +5V signal on pin 18 from the source. It responds by sending back a +5V signal to the source on pin 19, Hot Plug Detect (HPD). As shown in Figure 1:

Low Speed

If Hot Plug is asserted, the source will request for the sink to send its EDID, and also initiate the HDCP authentication protocol. The sink device will send its EDID table, which includes both supported and preferred (E-EDID) video resolution and timings, audio formats, and other data such as lip-sync delays. To learn more about EDID, see CEDIA’s Introduction to HDMI white paper.

After the EDID is read and optimal formats ascertained, the source will immediately send video to the display in order to present an image to the user as quickly as possible. If the content being delivered requires HDCP protection but authentication has not yet completed, an informative display will be sent, such as that shown in Figure 2. Content not requiring protection, such as a menu screen, may be displayed unimpaired.


Source

Pin 18+5V

Pin 18+5V

Pin 19Hot Plug Rx

Pin 19Hot Plug Tx

Sink

+5V

+5V HPD

Figure 1: Visual Display of HDMI Initialization Sequence

This content requires HDCP for playback.HDCP isn’t supported by your HDMI connection.

Figure 2: Informative display before HDCP authentication

13 © 2016 CEDIA

The purpose of HDCP is to ensure any incidence of interception or eavesdropping on the transmission cannot decipher the content. The HDCP process begins with the source sending its public key (HDCP 1.x) or an initialization message (HDCP 2.2) to the receiver. The receiver responds by sending its public key, along with a single bit to indicate if it is a repeater. Both devices then authenticate and combine public and private keys to establish a shared secret cipher.

The source uses this shared secret to encrypt the protected A/V content for transmission, with only the authorized receiver being able to decrypt it. The source then periodically checks for synchronization, and that the receiver is properly decrypting the content.

The source always controls the HDCP system. The arrangement of devices throughout the system is referred to as the HDCP topology, typically creating a tree-shaped structure. Every transmitter-receiver link in the system undergoes the same authentication process, but its the source that determines when the content may flow and to which devices.

HDCP can sometimes cause handshaking problems in which devices cannot establish a connection, especially with older high-definition displays. Problems are almost always in the source device, according to HDMI LLC, and tend to arise in one major area of implementation. Sources have to support a function called “authenticate forever,” which in layman’s terms means the source must consistently send a signal inquiring whether its HDMI input is selected, even while another input is in use [1]. If a source device times out and stops inquiring, an HDCP authentication failure will most likely result.

High Speed

Audio visual content is encrypted following HDCP authentication before being sent through the three TMDS channels in HDMI. Codes periodically included in the frame-blanking intervals include synchronization information. The receiver ackowledging that it has this data affirms that it is decrypting the data properly, which is checked by the source over the DDC channel. If synchronization is lost, the source will typically detect it within about 5 seconds.

For more information about HDCP, refer to the CEDIA white paper “HDCP 2.2 for Integrators,” or the more advanced “HDCP 2.2 Technical Insight.”


Figure 3: Visual Display of HDMI Initialization Sequence

+5V

Minimum 0.055A Source Sink

EDID sent upstream on DDC

e.g. I am a 32” LCD Max resolution 1920x1080, etc.

Source Sink

Source initiates HDCPSource Sink

Common secret established

HDCP Session commencesSource Sink

Sink

Send unencrypted video in TMDS;informative display or menu

Initialize HDCP authentication

Source

Hot Plug (5V) enabled at sink

Source: is anything there?Source Sink

Yes, then request status, EDID, etc.Source Sink

HDCP sync continues on DDC

Video is transmitted on TMDS

Source Sink

Send HDCP public key on DDCSource Sink

Source checks for validity

14 © 2016 CEDIA

06 CONCLUDING REMARKS

HDMI Initialization Sequence is a complex process, and it is important to have a good understanding of it. If one understands the initialization sequence, the ensuing troubleshooting of the system will be much easier. The technician or the system designer can diagnose based on the condition whether the source, sink, or repeater device is causing problems and needs replacement or a firmware upgrade. Troubleshooting will be the topic of a future white paper. In the next edition of this continuing series, we will cover the HDMI System Installation Best Practices.

07 REFERENCES

1. HDMI LLC. (n.d.). HDMI for Installers. Retrieved June 19, 2010, from HDMI LLC:

http://www.hdmi.org/installers/

2. Quantum Data Corporation. (2009). Designing CEC into your next HDMI product.

08 APPENDIX A: HDMI 1.4A FEATURES

HDMI 1.4a specification established protocols for a number of popular 3D display methods, including:

• Frame, line, or field alternative methods

• Side-by-side methods (full and half)

• 2D plus depth methods

3D video requires substantial data throughput, so a High Speed HDMI cable (with or without Ethernet) should be used, although standard HDMI cables will support the broadcast 3D formats (top and bottom, side by side).

The HDMI 1.4a specification has also added support for extremely high video resolutions that go far beyond today’s 1080p displays. 4K is shorthand for 4,000 lines wide by 2,000 lines high, or roughly four times the resolution of a 1080p display. Note that 4K resolution is 24p only, and therefore fits within the maximum data rate of a High Speed HDMI cable. Figure 2 shows the difference in quality between common display formats and 4K resolution.

The Audio Return Channel in HDMI 1.4a enables a TV to send audio data “upstream” to an A/V receiver or

surround audio controller, eliminating the need for any separate S/PDIF audio connection.

• An Audio Return Channel-enabled TV can either send or receive audio via HDMI, upstream or downstream, depending on system set-up and user preferences.

• LipSync functionality, introduced in HDMI 1.3, ensures that the audio stays matched to the video, automatically compensating for any processor delays whether the audio is traveling upstream or downstream.

The HDMI Ethernet Channel allows internet-enabled HDMI devices to share an internet connection via the HDMI link, with no need for a separate Ethernet cable. It also provides the connection platform that will allow HDMI-enabled components to share content between devices with speeds up to 100 Mbps [2].

The CEC bus is a one-wire “party line” that connects up to 10 A/V devices through standard HDMI cabling[4]. CEC will automatically power on the appropriate products, route the DVD/Blu-ray’s audio output through the A/V receiver to the attached speakers, and route the player’s motion picture to the digital TV[4]. CEC enables automatic equipment discovery and simple “one-touch” operation in HDMI interfaced systems. Most installers and designers prefer to turn off this functionality as it is usually not cross-brand compatible.

For information about HDMI 2.0, refer to CEDIA white paper “HDMI 2.0 & Ultra HD,” 2016.


Figure 2: A visual example of 4K Resolution Acquired from HDMI LLC

Figure 2: A visual example of 4K Resolution. Acquired from HDMI LLC.

http://www.hdmi.org/installers/

15 © 2016 CEDIA

HDMI InstallationBest Practices

WHITE PAPER

Revised Edition2016



03 Document Scope 18

04 Distribution Best Practices 18 Long-Haul Cables 18 Inter/Intra-Pair Skew 18 Active Cables and How to Pull HDMI Cables 18 Basic HDMI Tests 19 Bit Error Rate 19 Cat 5/6 and HDMI Extenders 19 HDBaseT Extenders 20 HDMI Fiber Solutions 20 HDMI Switching and Splitters 20

05 Interoperability Best Practices 21 EDID Issues 21

06 Conclusion 22

07 References 22

TABLE OF CONTENTS

17 © 2016 CEDIA

01 ACKNOWLEDGEMENTS

CEDIA would like to thank the following individuals for their review of the original publication of HDMI Best Installation Practices:Dave Hunt, Intuitive IntegrationDavid Meyer, KordzJames Chen, KordzRich Green, Rich Green Ink

Updated 2016 Revision by David Meyer; HDMI, HDCP, HDBaseT & UHD Subject Matter Expert and CEDIA Certified Instructor.


Audio Return ChannelThe audio return channel in HDMI 1.4a allows a TV to send audio data upstream to an A/V receiver, eliminating the need for a separate SPDIF audio connection. It supports the same audio formats as an SPDIF cable, which means it does not support high-definition audio or multi-channel PCM.

BERBit Error Rate. A continuous monitor of the number of digital bits delivered to an HDMI sink that are not readable and are therefore in error.

CECOne of the channels in an HDMI connection is dedicated to a set of advanced control functions, collectively known as Consumer Electronics Control or CEC. When enabled by the manufacturer, CEC functionality allows connected devices to control each other in useful ways. For instance, a single command on a remote control can be used to play a DVD or to launch other complex activities across multiple devices in a home theater system.

DDCDisplay Data Channel, one of the channels in an HDMI connection. DDC is a two-wire bus (data + clock) which is based on I2C Inter-Integrated Circuit protocol. It is used for communicating EDID (Extended Display Identification Data) information upstream from display to source, and also the HDCP keys downstream from source to sink.

EDIDExtended Display Identification Data, the data contained

(in a small memory called EEPROM) on each DVI display or HDMI sink which contains a table of supported video formats and timings, and audio formats, etc. The sink/display sends this table upstream to the source over the DDC wires in the HDMI cable, which the source reads in order to optimize the resulting output video and audio format. All sink devices compliant to the HDMI specification must implement EDID.

Eye Diagram TestAlso called an eye pattern, graphically depicts transmission of a digital signal. It indicates the readable width of a bit (>50% of the total width is acceptable), and also the amplitude (height). A good test result resembles the shape of an eye, the more open the better.

HDCPHigh-bandwidth Digital Content Protection. Developed by Intel, HDCP is an authentication system designed to protect copyrighted audiovisual content by encrypting it for transmission. All HDMI-enabled devices employ HDCP.

HDMI RepeaterA device that both receives and sends HDMI signals, such as an AV receiver.

Hot Plug DetectA function of HDMI connectivity that allows the source device to sense when a display device has been connected to it.

Inter/Intra-Pair SkewVariations in the twist of the cable, overall length of the copper cable and variations in the dielectric to insulate the wire can create an error such that positive and negative signals are skewed in time to one another.

JitterDeviation in or displacement of some aspect of the pulses in a high-frequency digital signal such as HDMI. This can be in terms of amplitude, or the phase timing, etc. It has the effect of closing in the eye pattern, reducing the readable size of the bit.

Matrix Switcher Matrix switchers route multiple audio/video sources to multiple audio/video destinations.

Nanosecond One billionth of a second (0.000000001 second).

HDMI INSTALLATION BEST PRACTICES

18 © 2016 CEDIA

Picosecond One trillionth of a second (0.000000000001 second).

SinkA device that receives an HDMI signal, such as an HDTV.

SourceA device that sends an HDMI signal, such as a DVD player or set-top box.

03 DOCUMENT SCOPE

HDMI Installation Best Practices is the third document in a series of white papers published by CEDIA. Previous documents include Introduction to HDMI and HDMI Initialization Sequence. These documents are available in the CEDIA Marketplace at www.cedia.org/marketplace. This document discusses best installation practices in distribution such as active cables, HDMI, Cat 5/6, and fiber solutions, as well as basic HDMI tests and interoperability

04 DISTRIBUTION BEST PRACTICES

LONG-HAUL CABLES

Before we start to discuss best practices for long-haul cabling, it is important to know how digital video signals are affected over long cable lengths. A cable is an imperfect transmission line, with electrical characteristics such as resistance, capacitance and skew adversely impacting signal integrity. Generally speaking, the longer a cable, the more the eye diagram closes, and once it hits a mimimum threshold of 50% closure, it fails HDMI compliance and will become unreliable or non-operational.

As transmission bit rate increases, as is the case with increasing video resolutions, the time interval of each bit becomes shorter. E.g. double the rate means each bit is half the length in time, and the eye diagram may suffer closure at around half the cable length. This is why (passive HDMI) cable length and supported video resolution are typically inversely proportional.

INTER/INTRA-PAIR SKEW

HDMI uses twisted pair cables, which are subject to two types of skew that can create timing errors and cause data drop-outs. The two types of skew are intra-pair skew and inter-pair skew. Intra-pair skew is the time differential between the two wires making up itself,

while inter-pair skew is the time differential between separate twisted pair lines in the cable assembly[1]. Total allowable intra-pair skew is only about 4.8 picoseconds, and inter-pair skew should not exceed 7.2 nanoseconds [13]. Because of these small tolerances, HDMI cable construction is of important significance to installers.

Some attributes to pay attention to include the cable gauge, cable material, and its impedance. Since allowable skew is fixed and the percentage error in cables (normally measured per meter) is constant, longer cables are more difficult to manufacture. The termination of HDMI cables is also a critical area, accounting for greater dB loss than the length of wires themselves may induce. These are key reasons why field-terminated native HDMI cables have never been a compliant option.

ACTIVE CABLES AND HOW TO PULL HDMI CABLES

Using cables with active electronics can boost and clean up the signal and almost double the range of a copper-twisted cable. Cable runs of up to 30 meters are typical for this type of solution, which can either be implemented through an HDCP-compliant repeater or incorporated into the manufacture of the cable itself. Active cables embed signal-enhancement electronics in the cable itself. High-speed channels in HDMI are mono-directional so care should be taken during installation to ensure proper directionality. Many of the solutions in this category require external power. In fact, HDMI Licensing recommends active (powered) extenders/boosters and recommends that they be powered by a separate power supply[2]. It is also important to note that there are very few high-speed capable active cables in the market at this time.

When pulling HDMI cables, remember the amount data flowing in the wire and treat it lightly. Do not yank the cable or twist connectors as the tolerances are tight[3]. It is important to note that HDMI Licensing does not currently support field-terminating products because of stringent skew and timing tolerances [2]. For in-wall installations, pull-through socks are available that will protect the connector as the cable is pulled through the wall or conduit.

If using an active cable, it is also recommended that the cable is run inside a conduit or has some future accessibility. As active cables utilize electronics, if the cable’s integrated circuit fails, then the only way to repair the cable is to replace it. Conduit will enable one to easily replace the defective cable without causing


19 © 2016 CEDIA

unnecessary holes/damage to existing walls. Be sure to follow all state and local codes when installing conduit.Lastly, please be aware of products that draw power from the +5 volt pin of the HDMI cable.

An HDMI transmitter has limited power capabilities, with the transmitter not required to provide for any more than 55mA, and the sink is not allowed to draw any more than 50mA on the +5V pin[4]. Many active devices in the market draw power from the source through HDMI. They are convenient for installers, but may exceed the current draw limit and damage may result.

BASIC HDMI TESTS

An eye diagram test is used to test the quality of the HDMI signal by the Authorized Test Centers (ATCs). The eye pattern test shows many aspects of the digital signal. Figure 2 shows a sample eye pattern test result. The following are the primary characteristics of the test:

Signal AmplitudeThe height of the eye represents the signal amplitude. It should not become smaller in height than the marked diamond-shaped area in the middle. Otherwise, the signal will be too small for the display to recover [5].

Timing JitterThe rising and falling edges of digital bits do not always appear at the same time. This is known as “jitter.” The internal width of the eye can’t become narrower than the diamond area in the middle or the display won’t recover data [5].

In other words, a wide opening, thin line, and symmetrical shape are indicators of high-quality HDMI cable. Any area of the diagram that touches the shape inside the eye called the “mask” represents a failure. Where available, installers must be careful to ensure the test results displayed are relevant – for the correct length, frequency and resolution because manufacturers do not implement HDMI the same way in their respective devices [3].

BIT ERROR RATE

Bit error rate (BER) testing shows the real number of bad bits a display could receive under a given condition. The higher the number, the worse the signal quality is. BER testing uses a signal generator to output billions of data bits, sending them to the cable

and receiving them from the other end of the cable[7]. Afterward, the received data is compared bit-by-bit with the sent data. The results will show the total number of error bits in a given period of time.

Figure 2: The “eye” pattern signal. Acquired from HDMI LLC.

CAT 5/6 AND HDMI EXTENDERS (NON-HDBaseT)

Cable runs of up to 50 meters can be achieved by sending the HDMI signal over Cat 5/6 networking cable using specially designed adapters. Unlike HDMI cables, Cat 5/6 cables can be field-terminated to a precise distance. Most non-HDBaseT single Cat 5/6 solutions use compression with a sink-side box reconstituting the HDMI signal from a decompressed signal. This can result in compression artifacts and reduced dynamic range/contrast [8]. The following are some best practices to follow when considering this solution:• A complete HDMI extender system consists of a

“transmitter” and a “receiver.” Both are required.• The power supply is sometimes connected to the

transmitter. Depending on the circumstances, better performance may be achieved by connecting the power supply at the receiver end [9].

• Some products require the two runs of CATx cable to be the same length. Check with the manufacturer.

• Always know the gear before designing it into a system and don’t try combinations on a jobsite without testing them first.

• Cat 6 cable may reduce the maximum distance due to tighter twists within the cable, but it still supports higher bandwidth and hence higher resolution.

• Dual CATx extenders are typically limited to 225MHz HDMI clock, which equates to 6.75Gbps. That means they will NOT support video resolutions greater than 1080p/60.


20 © 2016 CEDIA

• Maintain twists as close as possible to termination (no more than 0.5’’ untwisted) [2].

• Make gradual bends (radius should be four times the cable diameter or 1’’) [2].

• Use lubricant for tough pulls and grommets with metal studs [2].

Also be aware that sharp bends can cause permanent damage to the geometry of the cable and may result in transmission failure.

HDBaseT

HDBaseT has become ubiquitous amongst home technology professionals due to its ease of installation, single CAT6/7 with uncompressed signal transmission, and long-length capabilities. It’s based on 10G-BaseT Ethernet, but proprietarily modified for specialist audio visual applications.

The following are some best practices to follow when considering this solution:• A complete HDBaseT extender system consists of a

“transmitter” and a “receiver.” Both are required.• HDBaseT has far greater power draw requirements

than other solutions, and as such will require external power to operate. It is possible for an extender system to employ Power over HDBaseT (PoH, generally based on PoE or PoE+) to enable external power at one side only.

• Use only extenders which are certified by HDBaseT. These can be checked online at hdbaset.org

• Always know the gear before designing it into a system and don’t try combinations on a jobsite without testing them first.

• Certified transmitters and receivers may be mixed and matched, but be aware of the power requirements when doing so.

• Take care to check power requirements and support when combining transmitters or receivers with HDBaseT-integrated devices such as matrix switches wirth HDBaseT outputs, or projectors with a native HDBaseT input.

• Maintain twists as close as possible to termination (no more than 0.5’’ untwisted) [2].

• HDBaseT is limited to 10Gbps equivalent aggregate HDMI data rate. That means it will NOT support the advanced formats of HDMI 2.0, including UHD/30 with 10-bit 4:4:4 color.

HDMI FIBER SOLUTIONS

HDMI over fiber optic cable offers several advantages in long-haul applications, as these cables can transmit the signal more than 60 meters. Some of the disadvantages of fiber optic cable are that it cannot carry power and that it requires a box connected to an external power source. It is also not easy to achieve two-way communications as light travels in one direction. To solve these problems, manufacturers have used copper wires running alongside the fiber cables, which can weaken the fiber advantages [10]. Some things to keep in mind when looking for fiber optic solutions are [10]:• Look for HDCP 2.2 compliance (for UHD)• Look for minimum 18Gbps data rate support to

ensure full compatibility with all features and format timings of HDMI 2.0

• Ensure that effective distance is long and field termination is possible. Multi-mode fiber is generally adequate for distances <500ft, but check with the manufacturer as to what type of cable is recommended with the extender units

• Look for easy conduit pull (small cable head)

HDMI SWITCHING AND SPLITTERS

There are many types of HDMI switches available on the market. Simple HDMI switches have multiple inputs and a single output. Longer runs are possible via active electronics. An external power supply is required by HDMI LLC, and passive switches are deemed non-compliant.

HDMI splitters mirror one HDMI source to several displays. They are primarily used in sports bars or in retail stores, although they are becoming common in multi-room residential installations. An external power supply is required, and it can provide up to 127 outputs with HDCP. It is important to note that this is entirely dependent on source HDCP keys supporting this number of downstream devices and splitters supporting the appropriate level of cascading [8].

HDMI matrix switchers employ a series of HDMI transmitters and receivers with crosspoint switching in between, resulting in multiple inputs and outputs. An external power supply is required, and longer runs are possible with an HDBaseT transmitter on the output side of the switch.


http://hdbaset.org/

21 © 2016 CEDIA

Here are some features to look for when choosing an HDMI switcher:

• Right number of ports needed for the job• Automatic and manual switching• Make sure the device lists the features you want

it to support (i.e. UHD). HDMI LLC has moved to labels that must list the features not the version numbers.

• HDCP Version 2.2 pass-through. The higher the version supported, the better.

• For HDBaseT-equipped matrix switches, remember that data rate over 10Gbps cannot be supported, which limits vidoe format support.

Active switches, CATx, and fiber solutions can be chained together in combination, but doing so can significantly increase the jitter, adversely affecting the signal quality. Re-clockers can be used to increase input jitter tolerance [2], but may result in excessive HDCP levels, especially in a HDCP 2.2 system. For more information, see CEDIA’s white paper HDCP 2.2 for Integrators.

05 INTEROPERABILITY BEST PRACTICES

Interoperability issues are still plentiful and can create challenges for the installer. According to HDMI, most of the problems are limited to first-generation devices now. However, that’s changing with new UHD formats that introduce demands for higher data rates and HDCP 2.2 implications. With Ultra HD Blu-ray already putting out UHD/24 with 10-bit 4:4:4 color, the resulting 11.14Gbps data rate is beyond HDBaseT, and also beyond many long-haul HDMI cables, passive and active alike. Seeking out a reliable 18Gbps solution with HDCP 2.2 support is paramount in futureproofing for your clients.

The most common compatibility problem is the HDCP repeater function’s failure to perform reliably in all types of usage scenarios. Source devices need to properly implement the HDCP repeater function if a repeater (A/V receiver) will be installed in the system; otherwise, switching between source devices will result in an authentication failure [11].

HDCP can cause issues connecting multiple screens to a device. The source device manages the HDCP topology, which limits the number of devices and levels throughout the system. Product manufacturers may elect to support fewer devices and/or levels than the specification permits, but they cannot exceed it. In addition, sources need to support an HDCP function called “authenticate forever.” In layman’s terms, the source must consistently send a signal inquiring whether its HDMI input is selected, even while another input is in use. If a source device times out and stops inquiring, an HDCP authentication failure will probably result [3]. Since 2006, HDMI has mandated compliance testing for all products implementing HDCP. Lastly, until CEC 2.0 gains traction, we recommend turning off the CEC as it may interfere with other program devices installed and is usually not cross-brand compatible.

Following the recommended installation practices will reduce the installer’s or system designer’s need to troubleshoot the system in the first place. It is recommended to pre-qualify the HDMI system prior to installation and to check specifications and compatibility with legacy equipment in the client’s home. In addition, it is recommended to report installation issues to HDMI LLC, as they work with manufacturers to correct compliance issues and recall non-compliant products. In the next edition of the HDMI series, we will examine EDID sequencing.

EDID ISSUES

The acceptable video format(s), audio formats and lip-sync delays are listed in the sink’s EDID. The source can then select the output in accordance with the best possible format the sink supports. One key area of interoperability is for HDMI devices to communicate this EDID data via the DDC channel. Excessive capacitance or poor termination in the cables’ DDC wires can result in signal latency and collision, causing EDID and possibly also HDCP errors. If the source or repeater device fails to read the EDID correctly, the system will fail to select the proper audio and video modes [11].

According to HDMI LLC, it is a good idea for installers to take a small, reliable 1080p set along on installation calls to troubleshoot for this problem. If errors are present (improper resolution, etc.), the problem is most likely poor connectivity. It could also be the source device and may be resolved with a firmware update or replaced with a compliant source device [3].


22 © 2016 CEDIA

06 CONCLUSION

Following the recommended installation practices will reduce the installer’s or system designer’s need to troubleshoot the system in the first place. It is recommended to pre-qualify the HDMI system prior to installation and to check specifications and compatibility with legacy equipment in the client’s home. In addition, it is recommended to report installation issues to HDMI LLC, as they work with manufacturers to correct compliance issues and recall non-compliant products. In the next edition of the HDMI series, we will examine EDID sequencing.

07 REFERENCES

1. Extron Electronics. (2009). DVI and HDMI: The long and short of it.

2. Bodley, E. (2010, June). HDMI 1.4 for Custom Installers. Perfect Path Cables.

3. HDMI LLC. (n.d.). HDMI - Installers - Inside an HDMI cable. Retrieved June 19th, 2010, from HDMI LLC: http://www.hdmi.org/installers/insidehdmicable.aspx

4. HDMI Specification Version 1.4b, Section 4.2.7 Published October 11, 2011 by Hitachi Consumer Electronics, Panasonic

Corporation, Koninklijke Philips Electronics, Lattive Semiconductor (Silicon Image), Sony Corporation, Technicolor & Toshiba

5. Lu, X. (2008, July 31st). HDMI Demystified. AudioQuest.

6. Coleman, D. (2007, August 21st). How to Choose the Right HDMI Cable. Retrieved August 5th, 2010, from CE Pro: http://www.cepro.com/article/how_to_choose_the_right_hdmi_cable/

7. Lu, X. (2007, August 31st). Understanding HDMI “Eye Pattern”, “BER” and “Cliff Effect”. AudioQuest.

8. Chen, J. (2010, June 30th). EST 036: HDMI Update Seminar. Kordz.

9. Niles Audio (n.d.). CAT-5 HDMI Balun Application Notes.

10. Lu, X. (2010, July 25th). HDMI over Fiber Technology Overview. AudioQuest.

11. HDMI LLC. (n.d.). HDMI: Installers: Case Studies Retrieved June 19th, 2010, from HDMI LLC: http://www.hdmi.org/installers/case_studies.aspx


http://www.hdmi.org/installers/insidehdmicable.aspx

http://www.hdmi.org/installers/insidehdmicable.aspx

http://www.cepro.com/article/how_to_choose_the_right_hdmi_cable/

http://www.cepro.com/article/how_to_choose_the_right_hdmi_cable/

http://www.hdmi.org/installers/case_studies.aspx

http://www.hdmi.org/installers/case_studies.aspx

23 © 2016 CEDIA

Understanding EDID

WHITE PAPER

Revised Edition2016



03 Document Scope 25

04 Introduction to EDID 26

05 Reading Sink Device Capabilities from EDID 27 06 What Can Go Wrong with EDID? 27

07 EDID on Repeater Devices and Splitters 28

08 Checking EDID on Test Equipment 29

09 Conclusion 30

10 References 30

TABLE OF CONTENTS

25 © 2016 CEDIA

01 ACKNOWLEDGEMENTS



Audio Return ChannelThe audio return channel in HDMI 1.4a allows a TV to send audio data upstream to an A/V receiver, eliminating the need for a separate SPDIF audio connection. It supports the same audio formats as an SPDIF cable, which means it does not support high-definition audio or multi-channel PCM.

CECConsumer Electronics Control. One of the channels in an HDMI connection is dedicated to a set of advanced control functions, collectively known as CEC. When enabled by the manufacturer, CEC functionality allows connected devices to control each other in useful ways. For instance, a single command on a remote control can be used to play a DVD or to launch other complex activities across multiple devices in a home theater system.

CTAConsumer Technology Association - cta.tech

DDC Display Data Channel, one of the channels in an HDMI connection. DDC is a two-wire bus (data + clock) which is based on I2C Inter-Integrated Circuit protocol. It is used for communicating EDID (Extended Display Identification Data) information upstream from display to source, and also the HDCP keys downstream from source to sink.

EDIDExtended Display Identification Data, the data contained (in a small memory called EEPROM) on each DVI display or HDMI sink which contains a table of supported video formats and timings, and audio formats, etc. The sink/display sends this table upstream to the source over the DDC wires in the HDMI cable, which the source reads in order to optimize the resulting output video and audio format. All sink devices compliant to the HDMI specification must implement EDID.

HDCPHigh-bandwidth Digital Content Protection. Developed by Intel, HDCP is an authentication system designed to protect copyrighted audiovisual content. Most HDMI-enabled and DVI-enabled devices employ HDCP. HDMI RepeaterA device that both receives and sends HDMI signals, such as an AV receiver.

Hot Plug DetectA function of HDMI connectivity that allows the source device to sense when a display device has been connected to it.

I2CPronounced I-squared-C, alternatively called I2C or IIC. Abbreviation for Inter-Integrated Circuit, a bi-directional low speed bus developed by Philips for communication of data between chips either across a PCB or cable.



XMLExtensible Markup Language. XML is a set of rules for encoding documents in machine-readable format.

03 DOCUMENT SCOPE

Understanding EDID is the fourth document in a series of HDMI white papers published by CEDIA. Previous documents include Introduction to HDMI, HDMI Design and Initialization Sequence and HDMI Installation Best Practices. These documents are available in the CEDIA Marketplace at www.cedia.org/marketplace.

Understanding EDID introduces electronic systems contractors (ESCs) to techniques for reading and emulating sink device capabilities from EDID, gives an overview of EDID on repeater devices and splitters, and offers tips for resolving interoperability issues by examining the EDID.

The information provided in this document is for educational purposes only and is not a CEDIA endorsement of any manufacturer or product.

UNDERSTANDING EDID

https://www.cta.tech/

http://www.cedia.org/marketplace

26 © 2016 CEDIA

04 INTRODUCTION TO EDID

The HDMI initialization sequence consists of three activities: connection detection (hot plug), Plug and Play (EDID), and content protection (HDCP). EDID was created by VESA (Video Electronics Standards Association) to support Plug and Play[1]. EDID resides on a small chip called EEPROM in the HDMI sink or the input of an HDMI repeater device. All sink devices compliant with the HDMI specification are required to implement EDID [2]. HDMI EDIDs typically have two 128-byte blocks. The second block is the CTA extension block, and is required for HDMI as it contains display-specific information [1].

As described previously in Introduction to HDMI and HDMI Design and Initialization Sequence, Display Data Channel (DDC) is a low-speed (<100kbps) bi-directional communication bus that carries EDID from sink to source, and also provides the communication link for HDCP authentication and ongoing synchronization check. DDC is based on I2C protocol, equipped with arbitration and anti-collision capabilities to manage the bi-directional traffic.

An Extended Display Identification Data (EDID) query carried on the DDC channel prompts the display to respond with its manufacturer name, model number, and display capabilities to the source device. EDID describes the TV’s capabilities to the source device – for example, audio and video formats, lip sync delays, etc. HDMI employs a variation known as E-EDID, the additional prefix ‘E’ being Enhanced. This mode includes not only supported formats and timings, but also what is preferred by the display.

Successful communication of the EDID table from the sink device to the source device via the DDC channel is essential for interoperability.

For an installer, having access to EDID provides two useful functions [1]:

1. The ability to describe the supported functions of a display device.

2. The ability to use test equipment to emulate the interaction of a display with a source based on response to EDID.

The ability to describe the supported function of a display device as delivered by a manufacturer is important. While data sheets and operator manuals may be out-of-date, go out of print, or no longer be available, the easiest way to understand the display’s capabilities is to examine the EDID. Parsing the EDID into a human-readable form will give the installer an overview of any errors; for example, if a display device supports “side-by-side” 3D mode while the Blu-ray player doesn’t [1].

Emulation of a display device using its EDID is also a useful function for installers. To determine if an A/V receiver, DVD player, or HDMI switch is interoperable with a display device, using a saved EDID on the test equipment is a quick way to validate source device interoperability. This also provides a way to look for problems before a display is installed. Some set-top box (STB) manufacturers download new firmware to their equipment at midnight, and the client may find problems with the installed system the following day. Emulation of a display device with its EDID provides a way for an installer to tell the client that the display interaction was simulated with the STB originally using EDID and that the current problem is due to a new firmware download from the provider [1]. Many manufacturers provide test equipment to emulate the EDID.

UNDERSTANDING EDID

27 © 2016 CEDIA

05 READING SINK DEVICE CAPABILITIES FROM EDID

The following sink device capabilities are read from the EDID [1]:

VESA/CEA-861 Info HDMI Vendor-Specific Data Block

Product identification Max TMDS rate

Product name Dual link support

Manufacturer ID HDMI video timing support

Physical size of screen/aspect ratio 3D support

Standard video timing support 3D video timing support

Custom video timing with parameters 3D structures supported

Native video timing Separate 2D/3D video timing priorities (list)

Video timing priorities Deep color support

Color characteristics (XY of primaries) Support for content types (graphics, cinema, photo, game)

Wide gamut color Video latency

Selectable quantization range Audio latency

Selectable overscan/underscan DVD-Audio information support

Audio format support CEC physical address

Speaker allocation

06 WHAT CAN GO WRONG WITH EDID?

Potential complications with EDID include [1]:

• HDMI source never reads EDID, does not finish reading EDID, or does not read it properly

• HDMI sink does not support the video format that the HDMI source is sending

• Source may not output any video or will not output proper or optimal video

• HDMI extender alters the downstream EDID and/or changes formats

• HDMI source cannot read EDID and doesn’t output (at least) 640x480 when EDID is unreadable

• HDMI repeater is unable to merge a large number of EDID video timing descriptors (SVDs) from multiple downstream EDIDs

• HDMI repeater forwards the downstream sink’s EDID capabilities unmodified to the source

• Splitter device is hard-coded with an EDID or simply takes the EDID of the first device connected

• Sink declares a color mode of YCbCr (“color difference”) in its EDID, but doesn’t support both types of sampling modes (4:4:4 and subsampled 4:2:2 or 4:2:0).

If the EDID is corrupt, poorly formed, or incorrect, many audio or video problems can arise as a result. For example, the video resolution, color, or aspect ratio may not be correct. Additionally, the audio might not be in the desired format or might have the wrong number of channels.

UNDERSTANDING EDID

28 © 2016 CEDIA

Figure 1: Reading EDID on an A/V receiver (acquired from Quantum Data)

Source Device3-AV receiver generates hot-plug and the source reads the audio data from EDID of AV receiver’s sink side

4-Source device outputs audio based on the capabilities of the AV receiver’s EDID

AV Receiver’s Sink Side

AV Receiver’s Source Side

EDID (DDC) EDID (DDC)

AV Receiver2-AV receiver incorporates its audio data into the EDID and modifies (may reduce) the video timings, then forwards it to the source device

DTV1-Display device generates hot-plug and AV receiver’s source side reads audio from EDID of display

Audio

UNDERSTANDING EDID

EDID TRANSPORT & INTEROPERABILITY

When a physical HDMI connection occurs, the source checks for a hot plug assertion. If positive, the source will read the EDID of the HDMI sink device (HDTV or the input of a repeater or projector) on the DDC. The source will also verify that the EDID is intact, i.e. no header and checksum errors which may result from a transmission error on the DDC [1]. The source requires the EDID to determine an acceptable video format for the video output (HDMI/DVI, timing, color space, etc.) and the acceptable audio formats, channels, etc. (e.g. 2-channel LPCM or 5.1 Dolby Digital) [1].

All insulated wires are susceptible to capacitance, and the two wires that make up the DDC are no different. Capacitance is the ability of a material, in this case the wire’s insulation, to store electrical energy. EDID runs on a +3.3V bus, and the insulation will continually soak up and discharge this energy back into the wire, causing some latency in the signal. The higher the capacitance, the more the signal is degraded to the point that it may become unreadable. It may also compromise the anti-collision protocol of the I2C, disrupting HDCP authentication as well.

Permissible capacitance limits of the DDC wires in an HDMI cable is a tightly specified aspect of HDMI compliance and certification [3]. The HDMI specification states that capacitance cannot exceed 700 pF

(picofarads) in the cable, and 50pF in each of the source and sink devices [4]. Failure to comply (i.e. too much capacitance – VERY common) can lead to faulty EDID transmission and hence interoperability issues. As capacitance is a linear phenomenon, a 30-foot cable will typically have ten times the capacitance of a three-foot cable, meaning it is easy to go over the maximum capacitance level [3].

This is a major cause of interoperability problems, especially from long-length cables. Every length of cable, even in the same series, has different capacitance levels across all data lines, not just DDC, so it is important to ask the manufacturer for the specifications of a given cable (series and specific length) before procurement [3].

07 EDID ON REPEATER DEVICES AND SPLITTERS

When an AV receiver (a repeater device) is used in a system, the EDID should show the audio from the AVR, and the video should be the “intersection” of the video data from the AVR and the sink device [1]. The logical sequence of events when a repeater device is installed is shown in Figure 1.

29 © 2016 CEDIA

08 CHECKING EDID ON TEST EQUIPMENT

Connect test equipment to HDTV as shown:

• Read EDID

• Check for errors

• Verify video content

• Verify audio content

• Initiate hot plug and repeat

EDID can be loaded on a test instrument for HDMI using a computer or directly from a sink device. The EDID files are stored in XML format and can serve as a reference EDID to troubleshoot problems in the source device. For information on how to save the EDID and monitor DDC transactions, please consult the reference manual of the test equipment used. This functionality can help the technician explain to the client that the display’s interaction was simulated with the source using the stored EDID and the current problem is likely a result of a firmware download on the source device. It also provides a way to narrow down interoperability problems and look for faults before a display is installed. It is important to note that freeware software is available in the market that can also parse the EDID files to a human-readable form and give a description of the display’s supported features.

Figure 3: Sample EDID Test Set-Up

Figure 4: Sample screens of EDID test on 780 Handheld Test Instrument for HDMI, acquired from Quantum Data

UNDERSTANDING EDID

1:2 Splitter

Figure 2: EDID on splitter devices, acquired from Quantum Data

EDID (DDC) EDID (DDC)

AV Receiver2- Splitter processes EDID and may pass best common video and audio (“intersection”) in its EDID

1- Display device(s) generates hot-plug and splitter source side reads video & audio from EDID of display

Source Device3- Splitter asserts hot-plug and the source reads video and audio data from EDID of splitter sink side.

4- Source device outputs video and audio based on the least common capabilities (union) of the downstream device’s EDID

When splitter is used, the EDID can be one of the following: the “intersection” of the two devices, the EDID of the device connected initially, or a forced “provisioned” EDID [1]. An example of EDID sequencing with a splitter device is shown in Figure 2 below.

30 © 2016 CEDIA

09 CONCLUSION

EDID sequencing is a critical component of an HDMI system. Many common problems, such as incorrect video resolution and wrong audio format, can be attributed to a corrupt or poorly-formed EDID. Thus, it is important to describe the supported functions of a display device and to emulate the interaction of a display with a source based on the response to EDID. Testing tools provide a powerful application to extract EDID from a sink device and emulate it on a source device.

10 REFERENCES

1. Quantum Data Corporation. (2010). HDMI Installer Workshop: Basic Troubleshooting Tips.

2. CEDIA. (December 2010) Introduction to HDMI Interface.

3. Meyer, D. (2009, July 17th). ESD 031: HDMI Update Seminar. Kordz.

4. HDMI Specification version 1.4b (October 11, 2011) Section 4.2.8 DDC HDMI Licensing LLC and its founders.

5. CEDIA. (January 2011) HDMI Design and Initialization Sequence.

6. CEDIA. (February 2011) HDMI Best Installation Practices.

UNDERSTANDING EDID

31 © 2016 CEDIA

HDMI Troubleshooting

WHITE PAPER

Revised Edition2016


02 Glossary of Terms 33 03 Informative References 33 04 Document Scope 33

05 Troubleshooting the Principles 34 Defining the Problem 34 Identifying a Possible Cause 34 Diagnostic Sequence 34 Simplification 34 Substitution and Emulation 35 Passive Monitoring 35 06 Troubleshooting with Test Equipment 36 Sink Device 36 Source Device 36 Repeater Device 36

07 Conclusion 36

08 References 36

TABLE OF CONTENTS

33 © 2016 CEDIA

01 ACKNOWLEDGEMENTS


02 GLOSSARY TERMS

Audio Return Channel The audio return channel in HDMI 1.4a allows a TV to send audio data upstream to an A/V receiver, eliminating the need for a separate SPDIF audio connection. It supports the same audio formats as an SPDIF cable, which means it does not support high-definition audio or multi-channel PCM.

CECOne of the channels in an HDMI connection is dedicated to a set of advanced control functions, collectively known as Consumer Electronics Control, or CEC. When enabled by the manufacturer, CEC functionality allows connected devices to control each other in useful ways. For instance, a single command on a remote control can be used to play a DVD or to launch other complex activities across multiple devices in a home theater system.

DDCDisplay Data Channel, one of the channels in an HDMI connection. DDC is a two-wire bus (data + clock) which is based on I2C Inter-Integrated Circuit protocol. It is used for communicating EDID (Extended Display Identification Data) information upstream from display to source, and also the HDCP keys downstream from source to sink.

EDIDExtended Display Identification Data, the data contained (in a small memory called EEPROM) on each DVI display or HDMI sink which contains a table of supported video formats and timings, and audio formats, etc. The sink/display sends this table upstream to the source over the DDC wires in the HDMI cable, which the source reads in order to optimize the resulting output video and audio format. All sink devices compliant to the HDMI specification must implement EDID.

HDCPHigh-bandwidth Digital Content Protection. Developed by Intel, HDCP is an authentication system designed to protect copyrighted audiovisual content. Most HDMI-

enabled and DVI-enabled devices employ HDCP.

HDMI RepeaterA device that both receives and sends HDMI signals, such as an AV receiver.

Hot Plug Detect A function of HDMI connectivity that allows the source device to sense when a display device has been connected to it.



TMDSTransition Minimized Differential Signaling, a technology for transmitting serial data at very high speeds. TMDS is a core technology used in both DVI and HDMI.

03 INFORMATIVE REFERENCES

HD Sleuth, Audio Control. September 28th, 2010. Available in Apple iTunes App Store.

04 DOCUMENT SCOPE

HDMI Troubleshooting is the fifth document in a series of HDMI white papers published by CEDIA. Previous documents include Introduction to HDMI, HDMI Initialization Sequence, Best Installation Practices and Understanding EDID. These documents are available in the CEDIA Marketplace at www.cedia.org/marketplace.

HDMI Troubleshooting introduces troubleshooting principles for HDMI systems, helping readers identify possible causes of malfunction and simple troubleshooting techniques by inspection or using test equipment.

HDMI TROUBLESHOOTING



34 © 2016 CEDIA

05 TROUBLESHOOTING PROBLEMS

DEFINING THE PROBLEM

In order to properly identify the cause of a problem, one must first and foremost define the problem itself. If one fails to correctly identify what aspect of a system needs to be fixed, it will be hard to get to the root of the problem. The first steps toward defining the problem include:

• Writing down the specific symptoms being observed

• Documenting all the conditions and variables that may be affecting the system

IDENTIFYING A POSSIBLE CAUSE

With a basic understanding of how an HDMI system works, the technician can make an educated guess as to the cause of the problem based upon the symptoms being observed. Listed below are four of the most common HDMI connectivity problems as well as their likely causes [1].

Flashing Video - HDCP ErrorIf HDCP authentication fails, the source will continually attempt to authenticate the receiver device and continue to send the unencrypted video feed (HDCP informative display or ‘low value’ content). HDCP handshake authentication occurs approximately every one second.

No Video - Hot Plug ErrorIf the voltage received by the source on the hot plug line is outside of the specified range (+2.0V to 5.3V[2]), the source will not recognize that a receiver/sink device exists and will not initiate a session. Incorrect Format - EDID ErrorIf the EDID is not processed correctly from the sink device back to the source, the source device will send an incorrect or inferior quality signal based on incorrect information about the processing capabilities of the receiver device.

“Sparkles” or “Snow” in the video feed - Physical Layer Problem (Bad Cable/Connector/Board)If an HDMI cable or a circuit board in a device is poorly manufactured or of unsufficient bandwidth, bit errors will occur and introduce errors into the picture.

DIAGNOSTIC SEQUENCE

After identifying the possible causes, diagnostic procedures should focus on the cables as well as component(s) identified as a possible cause. Often there is more than one test with the test equipment that can be used to confirm that a component is the cause of the problem. Therefore, it is best to identify and use the diagnostic procedure that provides the most insight and is the most convenient to complete, as illustrated in Figure 1.

Figure 1: Use the diagnostic procedure that is most convenient and provides the greatest insights

Great Insights

Mo

st C

onv

enie

nt

SIMPLIFICATION

The goal when designing an HDMI system should be to have the simplest configuration. Reconfiguring a system to a more simplified connection path will eliminate variables that can compound the problem and increase the difficulty of troubleshooting the system. As the variables (devices or cables) are removed from the signal path, remember to only make one change at a time and test the system in between the changes. If a device or cable is removed and the system begins working properly, there is a possibility that the last device removed was the problem. In some cases, however, errors are additive, so there may not be a single culprit.


35 © 2016 CEDIA

SUBSTITUTION AND EMULATION

Once the problem is identified, possible causes should be documented, and the troubleshooting process should be defined. At that point, actual testing should begin. When working with an HDMI system, one of the simplest ways to test the signal path is through the substitution method. Using a known good HDMI source/sink device or test equipment capable of emulating an HDMI source/sink device by replacing components within the system, one can verify proper operation and discover the stage of the signal path where the problem is resolved.

PASSIVE MONITORING

Passively monitoring DDC transactions between devices in an HDMI system using test equipment will enable a technician to see the HDMI handshake between two devices without affecting it. This can be a huge advantage in identifying the root cause of HDMI handshake problems (i.e. hot plug, HDCP, and EDID problems) as well as possible permanent solutions. CORRECTIVE MEASURES

There are a limited number of things a technician can do on-site to correct a problem. In some cases, these corrective measures only get a system working for a single instance of an interoperability problem; in other words, they are workarounds. These workarounds may not be acceptable to a client. For example, initiating a hot plug or a power cycling sequence may free up a stuck HDMI port on an HDTV, but if the HDTV exhibited that problem once, it is likely to reoccur.

Temporary Corrective Measures

• Initiate hot plug by physically disconnecting the cable and then reconnecting it. A hot plug event will cause a reread of the EDID and an HDCP re-authentication.

• Turn all devices off, then turn on equipment one at a time, starting with the most downstream sink, letting each device stabilize before turning on the next device upstream.

• Turn on repeaters only after all downstream devices have been turned on and are stable. After the repeater is stable, make sure that it is selecting an active sink before powering on an upstream device.

• Lower the video resolution to 720p or 1080i first. If this is not possible, substitute analog video or SPDIF audio cables for HDMI.

Permanent Corrective Measures

• Replace with a higher-quality cable. Make sure to choose the best cable for the client’s needs. It is best to pre-test cables on the bench before installation, especially ahead of a pre-wire. Keep these new cables as short as possible.

• Add equalizer devices near the sink.

• Add a simple splitter or some other form of HDMI buffer in-between source and sink to arbitrate the signal. Some sink devices return the +5V line (pin 18) back through Hot Plug Detect (HPD, pin 19) via a 1,000-ohm resistor, which can cause detection issues with some sources that can’t pull-down the resistance again. Placing a buffer in between often resolves the problem.

• Replace older components and devices. Both the source and sink device may benefit from updated firmware and a newer HDCP version on later models.

• Replace HDMI extenders.

• Change HDMI ports on a component or device. HDMI ports are often not the same in terms of their transmit-and-receive characteristics.

• Update firmware, e.g. STBs, HDTVs, and PCs.

• Replace defective components and devices.

• Insert a switch or “correcting” device between components.

Replacing cables or equipment or updating firmware may be more involved than some of the temporary corrective measures previously discussed, but these steps are more likely to resolve the problem permanently. An important point to remember is that test equipment can confirm the root cause of a problem and verify that a solution is not simply a workaround. Test equipment can also be used to pre-qualify an HDMI system at the shop prior to an installation.

It is important to check the specifications of any products that you specify into an A/V system, including its inherent HDMI bandwidth and HDCP version compatibility on all input and output ports.


36 © 2016 CEDIA

06 TROUBLESHOOTING WITH TEST EQUIPMENT

Test equipment can be an invaluable tool when working with HDMI systems. There are advantages to troubleshooting with test equipment which cannot be accomplished by simple trial and error. The following are some of the advantages of using test equipment:

• Pre-screen products during procurement at the shop

• Pre-screen existing HDMI components in a client’s home

• Pull existing device EDIDs and emulate at the shop during system prequalification

• Reduce time on-site

• Quick diagnosis of causes

• Higher accuracy in confirming necessity of component replacement

• Reduce the likelihood of callbacks

• High degree of accuracy in confirming reliability of solution

• Preemptively identify potential future system failures

• Test equipment may also provide the client with a test report of functionality

The following are tests that can be performed on sink, source, or repeater device and will help to troubleshoot a system:

SINK DEVICE

• Verify if hot plug signal is high

• Verify EDID for a bad header, bad checksum, and pass/fail on compliance

• Check HDCP version and test authentication

• Test video at EDID preferred timing with HDCP enabled

• Tests sink’s support of EDID timings at primary formats: UHD (24/30/60), 1080p (24/30/50/60), 1080i (25/30), 720p (24/30/50/60)

• Test sink’s handling of supported video types and sampling (YCbCr 4:2:2 and 4:4:4)

• Test for deep color (mainly 10-bit) if supported

• Test HDCP reauthentication following port switch

SOURCE DEVICE

• Check HDCP version and test authentication

• Test source’s ability to respond to a known-good EDID

• Test for the maximum number of downstream devices a source can support with HDCP

• Test incoming video at various timings

• Test incoming video and verify timing, video type, and sampling (RGB, YCbCr 4:4:4 and 4:2:2)

REPEATER DEVICE

• Verify hot plug detect indication

• Verify EDID and verify whether EDID is passed through repeater and whether it is modified or not

• Test source’s ability to respond to a known-good EDID

• Verify that timing (resolution) of format is passed through repeater

• If timing is passed through, verify that video is passed through without any color or sampling

manipulation

• Verify HDCP authentication through repeater

• Verify whether the repeater acts as an HDCP repeater

• Verify HDCP authentication following port switch on repeater

07 CONCLUSION

Following HDMI installation best practices will help minimize the need for troubleshooting video systems. HDMI systems are often far more complex than meets the eye. When encountering difficulties within an HDMI environment, it is essential to use the troubleshooting techniques outlined in this document regardless of system complexity. Furthermore, using test equipment when troubleshooting HDMI will assist the installers in diagnosing and accurately rectifying the problem in a quick and efficient manner.

08 REFERENCES

1. Quantum Data Corporation. (2011). HDMI Installer Workshop: Diagnostic Principles & Techniques

2. HDMI Specification version 1.4b (October 11, 2011) Section 4.2.9 Hot Plug Detect Signal (HPD) HDMI Licensing LLC and its founders.


Documents

HDMI Fundamentals: A CEDIA White Paper Compilation · by CEDIA. Other white papers to follow include HDMI 101, installation best practices, understanding EDID, understanding and interpreting