Dolby Lake Analyer Bridge User Guide - Bodo Felusch · Chapter 1 Dolby® Lake® Analyzer Bridge User Guide 5 Introduction The Dolby® Lake® Analyzer Bridge provides an interface

Lake® Analyzer Bridge User Guide

ii Dolby® Lake® Analyzer Bridge User Guide

Dolby Laboratories, Inc.

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IT IS UNDERSTOOD AND AGREED THAT DOLBY LABORATORIES’ LIABILITY, WHETHER IN CONTRACT, IN TORT, UNDER ANY WARRANTY, IN NEGLIGENCE, OR OTHERWISE SHALL NOT EXCEED THE COST OF REPAIR OR REPLACEMENT OF THE DEFECTIVE COMPONENTS OR ACCUSED INFRINGING DEVICES, AND UNDER NO CIRCUMSTANCES SHALL DOLBY LABORATORIES BE LIABLE FOR INCIDENTAL, SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES, (INCLUDING, BUT NOT LIMITED TO, DAMAGE TO SOFTWARE OR RECORDED AUDIO OR VISUAL MATERIAL), COST OF DEFENSE, OR LOSS OF USE, REVENUE, OR PROFIT, EVEN IF DOLBY LABORATORIES OR ITS AGENTS HAVE BEEN ADVISED, ORALLY OR IN WRITING, OF THE POSSIBILITY OF SUCH DAMAGES.

Dolby, Lake, and the double‐D symbol are registered trademarks of Dolby Laboratories. Part Number 91516All other trademarks remain the property of their respective owners. Issue 2© 2008 Dolby Laboratories, Inc. All rights reserved. S08/17176/20332

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Dolby® Lake® Analyzer Bridge User Guide iii

Table of Contents

List of Figures............................................................................................................................ iv

Introduction................................................................................................................................. 5 Manual Overview.................................................................................................................................... 5

Overview...................................................................................................................................... 7

Requirements and Installation .................................................................................................. 9 3.1 Requirements............................................................................................................................... 9 3.2 Installation .................................................................................................................................... 9

Getting Started.......................................................................................................................... 11 4.1 Tray Icon Status and Tool Tips .................................................................................................. 11 4.2 Starting the Analyzer Bridge and Lake Controller...................................................................... 12 4.3 Measured and Reference Level Meters..................................................................................... 13

Function Reference .................................................................................................................. 15 5.1 Analyzer Bridge Top Level Interface.......................................................................................... 15 5.2 Spectrum RTA Measurement Mode .......................................................................................... 16 5.3 Spectrograph Measurement Mode ............................................................................................ 20 5.4 Transfer Function Measurement Mode...................................................................................... 22 5.5 Global Control Functions ........................................................................................................... 31

iv Dolby® Lake® Analyzer Bridge User Guide

List of Figures

Figure 2-1 Single Host Computer ................................................................................................................. 7 Figure 2-2 Two Computers Connected Across Ethernet Network................................................................ 7 Figure 2-3 Example Network Configuration.................................................................................................. 8 Figure 4-1 Analyzer Bridge Ready.............................................................................................................. 11 Figure 4-2 Analyzer Bridge Transmitting .................................................................................................... 11 Figure 4-3 Ethernet Adapter Initialization ................................................................................................... 11 Figure 4-4 Ethernet Adapter Error, Cannot Transmit, or Offline................................................................. 12 Figure 4-5 Analyzer Unavailable................................................................................................................. 12 Figure 4-6 Analyzer Available ..................................................................................................................... 13 Figure 4-7 Measured and Reference Channel Meters ............................................................................... 13 Figure 4-8 Clip Indication ............................................................................................................................ 13 Figure 4-9 SmaartLive Metering Unavailable ............................................................................................. 14 Figure 5-1 Analyzer Bridge Transfer Mode Delay Controls........................................................................ 15 Figure 5-2 Spectrum Measurement Mode .................................................................................................. 17 Figure 5-3 Spectrum Properties Submenu ................................................................................................. 17 Figure 5-4 Averages Submenu................................................................................................................... 18 Figure 5-5 FFT Size Submenu.................................................................................................................... 20 Figure 5-6 Spectrograph Measurement Mode............................................................................................ 21 Figure 5-7 Colormap Range ....................................................................................................................... 21 Figure 5-8 Speed Controls.......................................................................................................................... 22 Figure 5-9 Block Diagram of Transfer Function Measurement................................................................... 22 Figure 5-10 Transfer Function Measurement Mode ................................................................................... 23 Figure 5-11 Transfer Function Properties Submenu .................................................................................. 24 Figure 5-12 Averages Submenu................................................................................................................. 25 Figure 5-13 Smoothing Submenu............................................................................................................... 26 Figure 5-14 Coherence Display .................................................................................................................. 27 Figure 5-15 Default Phase Display (Phase Normal/Small)......................................................................... 28 Figure 5-16 Phase Large ............................................................................................................................ 29 Figure 5-17 Swap Enabled ......................................................................................................................... 30 Figure 5-18 Pause ...................................................................................................................................... 31 Figure 5-19 Signal Generator ..................................................................................................................... 31 Figure 5-20 Sample Rate............................................................................................................................ 31

Chapter 1

Dolby® Lake® Analyzer Bridge User Guide 5

Introduction

The Dolby® Lake® Analyzer Bridge provides an interface between the Dolby Lake Controller and third‐party audio analyzer software products.

Manual Overview

This manual provides software installation instructions, networking, and reference information for all features of the Analyzer Bridge and associated controls that become available in the Dolby Lake Controller.

The manual is organized as follows:

• Chapter 1, Introduction (this chapter). • Chapter 2, Overview, shows you how to connect and use the Analyzer Bridge with

the Dolby Lake Controller software. • Chapter 3, Requirements and Installation, guides you through the configuration of

Analyzer Bridge on your PC. • Chapter 4, Getting Started, provides an overview of Analyzer Bridge functionality. • Chapter 5, Function Reference, details all functions and modes of operation of the

Analyzer Bridge.

Chapter 2


Overview

The Dolby® Lake® Analyzer Bridge displays measurement results within the Dolby Lake Controller, and passes control information from the Dolby Lake Controller back to the third‐party analyzer software. This communication link can be provided on the same host computer, or across an Ethernet network to connect two computers as the following figures illustrate.

Figure 2-1 Single Host Computer

Figure 2-2 Two Computers Connected Across Ethernet Network

Figure 2‐1 and Figure 2‐2 illustrate the two possible communication configurations. The Analyzer Bridge automatically detects the correct communication method.

Figure 2‐3 shows a practical example connection for running the Analyzer, Analyzer Bridge, and the Dolby Lake Controller using two computers. The Analyzer PC running the third‐party analyzer software and the Dolby Lake Analyzer Bridge has a wired connection to an Ethernet switch that connects the entire Dolby Lake network. A wireless tablet PC running

Overview

8 Dolby® Lake® Analyzer Bridge User Guide

the Dolby Lake Controller is connected to the same switch using a wireless access point. This configuration allows you to transmit the analyzer results wirelessly to the Dolby Lake Controller.

Figure 2-3 Example Network Configuration

For further information on networking and hardware configuration, please refer to the Dolby Lake Controller Software Manual and the Dolby Lake Processor System Manual.

Chapter 3


Requirements and Installation

3.1 Requirements

To use the Dolby® Lake® Analyzer Bridge, the following items are required:

• A Microsoft® Windows® PC with a fully registered installation of an approved analyzer meeting the computer requirements for the analyzer. Approved analyzers include: • SIA Software: SmaartLive v.5.4.0.0 • WaveCapture: Live‐Capture Light v1.0 and Live‐Capture Pro v.1.0 Note: Support for additional analyzers may be added in the future; please refer to www.dolby.com or the Live Sound Support Forum for further details.

• A Windows PC with an installation of the Dolby Lake Controller, meeting the Dolby Lake Controller minimum computer requirements.

Operating the Dolby Lake Controller and your third‐party analyzer on the same computer may result in slow performance even where the required minimum specifications are met. The Lake Controller is graphic intensive, and audio analyzer software FFT calculation is also CPU intensive; therefore, the performance of the graphics card is important. A graphics card with slow performance or low video memory will reduce computer performance by the transfer of rendering and display data.

We highly recommend that the graphics card driver is updated to the latest version available from the graphics card manufacturer. Video drivers shipped with Microsoft Windows are generic and may not take full advantage of certain video card resources.

3.2 Installation

The Dolby Lake Analyzer Bridge must be installed on the computer that will be running your third‐party analyzer software.

Double click the setup file, DLABSetup.exe.

When the installation process is complete, the Dolby Lake Analyzer Bridge will automatically run.

http://livesoundforum.dolby.com/

Chapter 4


Getting Started

4.1 Tray Icon Status and Tool Tips

The Analyzer Bridge is a tray application. You will see the Analyzer Bridge icon in the application tray typically found in the bottom‐right corner of the Microsoft® Windows® taskbar.

The Analyzer Bridge is configured to start when Windows starts, because it works as a background process in conjunction with your analyzer. If you would like to change this behavior, remove the shortcut to the Analyzer Bridge in the Windows Startup directory. The Analyzer Bridge tray icon provides status information and tool tips as well as alerts to network or adapter selection problems.

When correctly configured with your analyzer off, the tray icon tool tip displays a ready status:

Figure 4-1 Analyzer Bridge Ready

When the analyzer is turned on, the tray icon will rotate and the tool tip displays a transmitting status:

Figure 4-2 Analyzer Bridge Transmitting

If the tray icon displays a yellow line, the Analyzer Bridge is initializing the Ethernet adapter. You should only see this condition immediately following a network adapter selection, or during Windows startup.

Figure 4-3 Ethernet Adapter Initialization

If an error occurs with the currently selected Ethernet adapter, or you have selected offline operation, a red line is displayed across the tray icon. This condition will occur if you disable

Getting Started


the selected network adapter or if another transmission problem occurs. This condition can be fixed by selecting a valid network adapter.

Figure 4-4 Ethernet Adapter Error, Cannot Transmit, or Offline

4.2 Starting the Analyzer Bridge and Lake Controller

When your analyzer is running, you will see the Dolby® Lake® Analyzer Bridge icon rotating in the Windows tray icon area.

When the Dolby Lake Controller starts up, it checks to see if both the Analyzer Bridge and your Analyzer are operating, either on the same computer or across the network. If the Dolby Lake Controller cannot find an approved analyzer or the Analyzer Bridge, it will show “Analyzer Unavailable” as the F10 button on the PEQ, GEQ, and XOVER Overlays within each module. Tapping this button will display a warning dialog with further information.

Figure 4-5 Analyzer Unavailable

Measured and Reference Level Meters


If the Dolby Lake Controller detects the Analyzer Bridge and a valid analyzer on the network, the Analyzer Bridge button (F10) is activated, allowing entry into the submenu for controlling your analyzer.

Figure 4-6 Analyzer Available

4.3 Measured and Reference Level Meters

Metering is displayed in the bottom right corner of the Dolby Lake Controller. This feature allows remote monitoring of the reference and measured audio channels on the analyzer PC.

Metering is displayed when analyzer data is being transmitted via the Analyzer Bridge. Two meters are shown, one for the measured channel and one for the reference channel:

Figure 4-7 Measured and Reference Channel Meters

Channel clipping is indicated on each channel, and the entire meter will change to red if either channel is clipping.

Figure 4-8 Clip Indication

Note: For SmaartLive v.5.4, metering is available only when SmaartLive is the currently selected application on the analyzer PC. Metering will not be available if another application is running on top of SmaartLive. If the Analyzer Bridge cannot obtain metering information, it will display “SmaartLive Metering Unavailable.”

Getting Started


Figure 4-9 SmaartLive Metering Unavailable

You can correct this error condition by ensuring that SmaartLive is the currently selected application on the analyzer PC.

Chapter 5


Function Reference

This section details each function of the Dolby® Lake® Analyzer Bridge. Most functions are provided through the Dolby Lake Controller Toolbar interface. Common functions are provided at the top of the EQ and XOVER Overlay tabs.

5.1 Analyzer Bridge Top Level Interface

When you first enter the Analyzer Bridge submenu, you will see a new set of controls at the top of the Lake Controller display. Depending on your analyzer, the delay controls shown in Figure 5‐1 may not be displayed when in Spectrum/Spectrograph mode.

Figure 5-1 Analyzer Bridge Transfer Mode Delay Controls

Reseed Avg Reseed Averages clears the averaging buffers (used to increase the stability of the live traces). This forces your analyzer to ʺreseedʺ the averaging buffers with fresh data. The plot will require a short period of time to restabilize while the buffers are filled.

Note: Changing the number of averages, FFT size, or sampling rate, or switching between main display modes, also reseeds the averaging buffers.

Delay Controls The Analyzer Bridge provides five delay controls, grouped together at the top of the display. These controls are mainly used to provide signal alignment between the reference and measurement signals for transfer function measurements.

The delay value is displayed in milliseconds in the Delay edit field. To change the delay value, tap this edit field and enter the required delay using the onscreen keyboard.

The Delay+ and Delay‐ buttons to the right of the Delay edit field can be used to decrease and increase the current Delay setting by 0.01 millisecond.

Function Reference


Delay Controls (continued)

Your third‐party analyzer can find the time offset (delay) between two input signals by measuring the impulse response of the device or system under test. The physical measurement setup for delay measurements is identical to the setup used for Transfer Function measurements, requiring both a reference (source) signal and a measurement (return) signal. SmaartLive v.5.4.0.0 The auto‐delay measurement is activated by clicking [Auto Sm] or [Auto Lg] buttons to the right of the Delay+/‐ buttons. The small (sm) (up to 300 ms) and large (lg) (up to three seconds) options refer to the time window used in the measurement routine. It is essential that the time window used in the measurement is relative to the decay time of the room/system under test. Live Capture Light/Pro v1.0 The Auto Sm and Auto Lg buttons perform the same function—it is the FFT size that determines the maximum available delay. Live Capture uses an advanced delay autolocator based on an energy‐time correlation algorithm, which removes the need or for small or large time windowing. For example, when an FFT size of 8 kS is used in combination with 48 kHz sample rate, the maximum delay is 170 ms (less approximately 50 ms used for time window = 120 ms). For a longer delay time, increase the FFT size via the analyzer settings. Please refer to individual analyzer documentation for further information.

Spectrum, Spectrograph and

Transfer

The top level interface of the Analyzer Bridge provides three buttons to enter the three measurement modes. Spectrum and Spectrograph are single‐channel FFT measurement functions. Transfer function is a dual‐channel measurement function. Each of these measurement modes is detailed in the measurement mode function references that follow.

5.2 Spectrum RTA Measurement Mode

The Spectrum mode RTA displays functions as a real‐time spectrum analyzer. This display plots the spectrum (magnitude values by frequency) of the measurement channel soundcard input.

The RTA plot puts magnitude on the (vertical) y‐axis and frequency on the (horizontal) x‐axis. This information is calculated in different ways depending on the analyzer being used. Please refer to your analyzer documentation for further information.

When the Spectrum RTA button is selected, the Dolby Lake Controller will show the RTA display on EQ and Auxiliary Overlays.

Spectrum RTA Measurement Mode


Figure 5-2 Spectrum Measurement Mode

The y‐axis scale of the RTA is displayed on the right side of the Lake Controller interface. The Spectrum Properties button at the bottom of the interface provides access to Spectrum specific functions.

Figure 5-3 Spectrum Properties Submenu

Function Reference


Averages The three basic averaging schemes used are linear first in, first out (FIFO), infinite, and exponential (fast, slow, and variable). Note that these are the same for Transfer Function and Spectrum modes. FIFO averaging is a simple ʺarithmeticʺ average of some number (2, 4, 8, 16...) of the most recent FFT frames with equal ʺweightʺ given to each. The settings for FIFO averaging are in multiples of two because every doubling of the number of frames going into the average increases the signal‐to‐noise ratio of the measurement by 3 dB. If the Avg spinner is set to 1, no averaging is performed and only the data from the most recent FFT frame is plotted. Infinite (Inf) averaging also gives equal weight to each FFT measurement included in the average but rather than including only a fixed number of FFT frames, infinite (Inf) averaging keeps a running of average of all the FFT data that comes in until the averaging buffers are flushed (reseeded). You can force the averaging buffers to reseed at any time by pressing the Reseed Avg button at the top of the display. Averaging buffers are also flushed automatically whenever you change averaging parameters, change FFT size or sampling rate, stop the analyzer, or switch between main display modes. Unlike FIFO and infinite averaging, exponential averaging gives more relative weight to the most recent data going into the average while the weight of the oldest data ʺdecaysʺ exponentially. The options labeled Fast and Slow are exponential averaging routines with a fixed half‐life modeled on the characteristics of time integration circuits in standard sound level meters. Each doubling of the number of averages will increase the signal‐to‐noise ratio of the measurement by 3 dB (until the absolute noise floor of the system under test or the measurement system, whichever is higher, is reached). Note, however, that increasing the number of averages also causes real‐time displays to respond more slowly to changes, which can be more desirable in some circumstances than others. When you enter the Averages submenu, the Lake Controller displays a scrollbar with available averaging schemes. Select the desired averaging and then select the Average Select button. The status text between the scrollbar and the toolbar shows current parameters.

Figure 5-4 Averages Submenu

Spectrum RTA Measurement Mode


Amplitude Range

Move Primary Up: Moves the displayed range of the primary display upward to show higher magnitudes. Move Primary Down: Moves the displayed range of the primary display downward to show lower magnitudes. Zoom Primary In: Magnifies the displayed vertical range of the primary display for most plot types or narrows the magnitude range of the Spectrograph display. Zoom Primary Out: Decreases magnification of the vertical range of the primary display for most plot types or widens the magnitude range of the Spectrograph display.

Frequency

Range Move Primary Right: Moves the displayed range of the primary display to the right to show higher frequencies. Move Primary Left: Moves the displayed range of the primary display to the left to show lower frequencies. Zoom Primary In: Increases horizontal ʺmagnificationʺ of the primary display by decreasing the size of the range displayed. Zoom Primary Out: Decreases horizontal ʺmagnificationʺ of the primary display by increasing the size of the range displayed.

Freq Scale The Frequency Scale submenu lists the available display options for the

horizontal (x‐axis) scaling of the RTA. 1/24‐Octave, 1/12‐Octave, 1/6‐Octave, 1/3‐Octave and Octave resolutions are supported.

Function Reference


FFT Size For both real‐time spectral and frequency response (Transfer Function) measurements, one of the most important implications of the FFT parameters you select is the frequency resolution of the FFT. The frequency resolution of FFT data is a function of the FFT size and sampling rate. The practical implication of all this is that getting good detail at very low frequencies may require increasing the FFT frequency resolution either by increasing the FFT size or by decreasing the sampling rate. Note that either approach increases the FFT time constant (the amount of time required to collect all the samples for a given FFT size at a given sampling rate). The trade‐off is that time resolution effectively decreases as frequency resolution increases because each FFT then represents a longer period of time and because larger FFTs take longer to process. As a result, rapid changes in the input signals data may be masked as the FFT time constant is increased. As a rule of thumb for real‐time measurements, when looking at the entire audio spectrum, an 8 kHz FFT size at 44.1 or 48 kHz sampling rates provides a reasonable level of detail for low frequencies and still allows for reasonably good RTA ballistics on most machines. You will want to increase the FFT size and/or decrease the sampling rate to get better detail at very low frequencies. When you are more concerned with transient events and whatʹs happening at higher frequencies, use higher sampling rates and smaller FFT sizes to provide faster display updates and more detailed time resolution. In Spectrum and Transfer Function modes, there is one combined control for selecting FFT size. When you enter the FFT size submenu, the Lake Controller displays a scrollbar with available FFT sizes. Select the desired size, and then select the FFT Set Size button. The status text between the scrollbar and the toolbar shows current parameters.

Figure 5-5 FFT Size Submenu

5.3 Spectrograph Measurement Mode

The Spectrograph is a second type of RTA display that provides a way of looking at the frequency content of an input signal over some period of time. Instead of showing you the results of only one measurement at a time (whether averaged or instantaneous), as is the case on the Spectrum display, the Spectrograph can show you a record of the most recent 100 frames or more.

Spectrograph Measurement Mode


One way to think about the Spectrograph display is in terms of a common real‐time spectrum analyzer (RTA). On a typical RTA display, magnitude values for each fractional octave frequency band are indicated by vertical bars of varying height. If, instead of rising to a different height, each frequency band (or individual FFT bin) changed color to indicate higher or lower magnitude, you would end up with a horizontal line made up of different colored segments that showed the spectrum of a signal at a given moment.

The Spectrograph display effectively shows you three‐dimensional data (time, frequency, and energy) on a two‐dimensional plot with time on the y‐axis, frequency on the x‐axis, and magnitude represented by color. Exactly which color represents which magnitude value is determined by the magnitude range currently specified, the number of colors used, and the selected start and end colors.

Figure 5-6 Spectrograph Measurement Mode

Colormap

Range The magnitude range of the Spectrograph colormap is displayed on the top of the Spectrograph display. Two edit fields are provided to adjust the minimum and maximum range values for the colormap. Selecting one of these edit fields will bring up the onscreen keyboard to make changes.

Figure 5-7 Colormap Range

Function Reference


Speed Two buttons are provided to increase or decrease the speed of the Spectrograph. By adjusting the speed of the Spectrograph, you can increase or decrease the amount of time it takes for data to traverse the display.

Figure 5-8 Speed Controls

The Spectrograph measurement mode is controlled by all of the settings under Spectrum Properties, as detailed in the previous Spectrum RTA Measurement Mode function reference.

5.4 Transfer Function Measurement Mode

Your analyzer’s real‐time Transfer Function measurement capability is an extremely useful tool for setting up sound system equalizers and crossovers. A transfer function is a mathematical comparison of complex FFT data from two signals (typically the input and output of a device or system under test). This calculation is used to find how one signal differs from the other.

By comparing what goes into a device or system with what comes out, the transfer function calculates its frequency (magnitude and phase) response very precisely. A major advantage of this dual‐channel approach is that it works with a wide variety of test signals, including music or other recognizable program material.

To make a transfer function measurement, a test signal is split at the source and sent to both the system under test and the Right channel soundcard input on your computer. This will be the reference signal. The output of the system is returned to the Left channel soundcard input. This is the measurement signal.

Figure 5-9 Block Diagram of Transfer Function Measurement

In Transfer Function mode, FFT calculations are performed using audio data from the two inputs. This data is compared and displayed as a single trace showing the relative magnitude difference between the two signals frequency by frequency.

The default Transfer Function mode Magnitude display plots magnitude values on the y‐axis with 0 dB in the center and positive and negative decibel values above and below the zero line. The x‐axis of the plot shows frequency and is normally displayed in logarithmic scaling with grid lines at octave intervals. On the standard magnitude display, a value of 0 dB for a given frequency data point represents an equal amount of energy (that is, a relative

Transfer Function Measurement Mode


difference of zero) in both the reference (system input) and measurement (system output) signals at that frequency. A positive or negative decibel value for a given frequency indicates more or less energy in the measurement signal relative to the reference signal at that frequency. The Phase display in Transfer Function mode is a second plot showing the relative difference in phase between the two signals for each frequency.

Figure 5-10 Transfer Function Measurement Mode

The controls at the top of the Transfer Function display provide easy access to common controls, and include some of the same functions in the Analyzer Bridge Top Level Interface. The y‐axis scale of the Transfer function is displayed on the right side of the Lake Controller interface.

Reseed Avg Reseed Averages clears the averaging buffers (used to increase the stability of the live traces). This forces your analyzer to ʺreseedʺ the averaging buffers with fresh data. The plot will require a short period of time to restabilize while the buffers are filled.

Note: Changing the number of averages, FFT size, or sampling rate, or switching between main display modes, also reseeds the averaging buffers.

Function Reference


Coher (%) Coherence is a measure of the linearity between two signals in a transfer function measurement. The Coherence function basically asks ʺWhat are the chances that the signal that went into the system became the signal that came out as a result of a linear process?ʺ Coherence values are given as a percentage, where 100% equals perfect coherence.

Values closer to 1 mean better linearity and therefore better data. It is important to note that low coherence values do not necessarily mean your data is untrustworthy. This is particularly true when making acoustic measurements in noisy environments where a lot of averaging is required.

Select the Coher (%) edit field to adjust the Coherence Threshold percentage.

Mag (%) Another way of keeping bad data out of transfer function measurements is to use Magnitude Thresholding. This feature works by allowing you to set a threshold for the signal level, below which the analyzer will reject incoming data in the measurement signal on a frequency‐by‐frequency basis. When Magnitude Thresholding is on, every frequency data point in the signal is analyzed. If any data point falls below the threshold, the corresponding point in the transfer function trace will not be plotted when the transfer function display updates.

There are two real benefits to this feature, particularly when using your analyzer during a performance or in any other noisy environment. One is that it helps keep data off the screen that could not have originated from the system being measured (the assumption being that if you didnʹt put anything into the system at a given frequency, you shouldnʹt be getting anything out at that frequency). The other is that because the last valid data point measured remains on the screen until it is replaced by new valid data, this feature prevents the transfer function trace from ʺblowing upʺ when a song ends or the stimulus signal stops. The transfer function trace may also take a while to ʺbuildʺ when you begin measuring. If you donʹt see the trace starting to build after a few seconds, you may need to drop the threshold point.

Select the Mag (%) edit field to adjust the Magnitude Threshold percentage.

Delay Controls

Please refer to the information in Section 5.1.

The Transfer Properties button at the bottom of the interface provides access to Transfer Function specific functions.

Figure 5-11 Transfer Function Properties Submenu



Averages Several averaging options are available via the Transfer Function mode to help make the display more stable and easier to interpret. At the top level, there are two primary averaging options: Root Mean Square (RMS) and Vector averaging. The terms Vector and RMS refer to the type of data used in the averaging routine. There are also three different ways of averaging this data, irrespective of the type.

RMS averaging is also used in Spectrum mode to improve the signal‐to‐noise ratio of measurements and help stabilize the RTA and Spectrograph displays. Vector averaging is available only in Transfer Function mode.

You can choose between RMS and Vector averaging by selecting one of the two buttons on the Averaging submenu in Transfer Function mode.

When you enter the Averages submenu, the Dolby Lake Controller displays a scrollbar with available averaging schemes. Select the desired averaging, and then select the Average Select button. The status text between the scrollbar and the toolbar shows current analyzer parameters.

Please refer to your analyzer documentation for further information regarding averaging.

Figure 5-12 Averages Submenu

Amplitude Range

Lock to Analyzer: Locks the Lake Controller’s Overlay interface amplitude range to the current analyzer’s amplitude range. Move Primary Up: Moves the displayed range of the primary display upward to show higher magnitudes. Move Primary Down: Moves the displayed range of the primary display downward to show lower magnitudes. Zoom Primary In: Magnifies the displayed vertical range of the primary display for most plot types or narrows the magnitude range of the Spectrograph display. Zoom Primary Out: Decreases magnification of the vertical range of the primary display for most plot types or widens the magnitude range of the Spectrograph display.

Function Reference


Frequency Range

Move Primary Right: Moves the displayed range of the primary display to the right to show higher frequencies. Move Primary Left: Moves the displayed range of the primary display to the left to show lower frequencies. Zoom Primary In: Increases horizontal magnification of the primary display by decreasing the size of the range displayed. Zoom Primary Out: Decreases horizontal magnification of the primary display by increasing the size of the range displayed.

Smoothing Smoothing is another type of averaging that is available only in Transfer

Function mode. This feature helps to reduce jaggedness on the transfer function trace and can make trends in the device or system response easier to see.

Figure 5-13 Smoothing Submenu



Coherence Selecting the Coherence button will turn on the Coherence trace display. The

Coherence is displayed in red on the top of the Overlay display. The Coherence y‐axis scale is displayed in red on the right side of the display.

Figure 5-14 Coherence Display

Function Reference


Phase Selecting the Phase button will turn on the Phase trace display. By default, the phase is displayed in blue on the bottom of the display.

Figure 5-15 Default Phase Display (Phase Normal/Small)

The Phase Properties button provides access to Phase specific Transfer Function functions.

Phase Normal/ Phase

Alternate

On the default Phase display plot, all phase values are plotted within a 360° range of +180° to –180°, with 0° in the center [wrapped phase]. This 360° range represents one complete cycle of delay at any given frequency. You can also choose to view the phase within a 360° range of 0° to 360° (alternate phase). This is useful if there is a reverse of signal polarity within your transfer function measurement setup. Please refer to your analyzer documentation for further information regarding phase and the implementation of these options.



Phase Large/ Phase Small

By default, the phase is displayed in the bottom of the Lake Controller display. This small phase display is useful for providing an overview of the phase response. You can choose a larger display of the phase by selecting the Phase Large button. This displays the phase within the main Overlay display.

Figure 5-16 Phase Large

Function Reference


Swap Pressing the Swap button in Transfer Function mode transposes (swaps) the inputs to the Transfer Function calculation, so your analyzer divides the reference signal at the Right input (channel 1) by the measurement signal at the Left input (channel 0). This feature is mainly used when you want to display the inverse (upside‐down) magnitude response curve of an EQ or processor channel to facilitate using the room/system response as a template for setting EQ filters.

Figure 5-17 Swap Enabled

Global Control Functions


5.5 Global Control Functions

There are a handful of functions that affect the overall operation of your third‐party analyzer. These functions are provided on the button bar of the top‐level interface of the Analyzer Bridge submenu.

Pause This command pauses your analyzer in Spectrum and Transfer modes, and the measurement trace remains frozen on the screen. Pause is a toggle command. To resume processing data in real time when paused, deselect the Pause button.

Figure 5-18 Pause

Signal Generator

This command turns the analyzer signal generator on or off. When the button is selected, the Signal Generator is turned on. To choose the type of generated signal or adjust the gain of the signal generator, you must perform this adjustment through your analyzer user interface.

Figure 5-19 Signal Generator

Sample Rate Depending upon your soundcard capabilities, you can change the sample rate at which the Analyzer Bridge operates. You can choose from 44.1, 48, or 96 kHz sampling rates.

Figure 5-20 Sample Rate

Documents

Dolby Lake Analyer Bridge User Guide - Bodo Felusch · Chapter 1 Dolby® Lake® Analyzer Bridge User Guide 5 Introduction The Dolby® Lake® Analyzer Bridge provides an interface