Aac Vision Document v1.6

8/2/2019 Aac Vision Document v1.6

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Revision HistoryDate Version Description Author

10/20/08 1.0 Description of introduction and scope. Marcelo Santana

10/25/08 1.1 Alternatives in competition. Marcelo Santana

11/28/08 1.1 Project purpose. Marcelo Santana

11/18/08 1.2 Assumption, dependencies and constraints. Marcelo Santana

11/22/08 1.2 Product features. Marcelo Santana

11/27/08 1.3 Performance requirements and revision inassumption, dependencies and constraints.

Marcelo Santana

11/28/08 1.4 Revision. Wagner Oliveira

11/30/08 1.5 Reevaluation in assumption, dependencies

and constraints.

Marcelo Santana

12/01/08 1.6 Reevaluation in assumption, dependenciesand constraints.

Marcelo Santana

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Table of Contents

Figures......................................................5

Tables.......................................................5

1. Introduction ............................................. 3

1. Scope.....................................................................3

1. Scope......................................................3

2. Definitions, Acronyms and Abbreviations ..........................3

2. Definitions, Acronyms and Abbreviations ........3

3. Document Structure...................................................4

3. Document Structure...................................4

2. Project Purpose ......................................... 4

3. Stakeholder and User Descriptions ................. 4

1. Stakeholders............................................................4

1. Stakeholders.............................................4

2. Users.....................................................................5

2. Users......................................................5

3. User Environment......................................................5

3. User Environment......................................5

4. Alternatives and Competition........................................5

4. Alternatives and Competition........................5

4. Product Overview ...................................... 6MPEG-2 AAC-LC Decoder aac_vision_document_v1.6.odt Page 3/12


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1. Product Capabilities...................................................6

1. Product Capabilities...................................6

2. Product Features.......................................................6

2. Product Features.......................................6

1. Licensing ................................................................6

1. Licensing ................................................6

2. Deliverables and Installation.........................................6

2. Deliverables and Installation.........................6

3. Assumption, Dependencies and Constraints........................7

3. Assumption, Dependencies and Constraints......7

5. Other Product Requirements ........................ 7

4. Applicable Standards..................................................7

4. Applicable Standards..................................7

5. Hardware and Environmental Requirements.......................7

5. Hardware and Environmental Requirements.....7

1. Performance Requirements...........................................7

1. Performance Requirements..........................7

6. References ............................................... 8



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Figures

[Note: if the document doesnt have any figures, delete this topic.]

Tables

[Note: if the document doesnt have any tables, delete this topic.]

Table 1. Definitions, acronyms and abbreviations.....3

Table 2. Project Stakeholders..............................4

Table 3. Product Users.......................................4



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1. Introduction

The purpose of the Vision Document is to gather all of the information about thestakeholders and users of the MPEG-2 AAC-LC Audio Decoder. Their roles, needs andhow the MPEG-2 AAC-LC Audio Decoderfulfills these needs.

Developed by AT&T Corporation, Dolby Laboratories, the Fraunhofer Institute forIntegrated Circuits and Sony Corporation, the AAC (Advanced Audio Coding) wasstandardized under the joint direction of the International Organization ofStandardization and the International Electro-Technical Committee as part of theMPEG-2 specification in 1997 [1].

Initially, AAC was defined by 13818-3 as a multi-channel extension to MPEG-1 (thestandard defining MP3) and was backwards compatible with MPEG-1. However, AACwas limited by the MPEG-1 standard, and 13818-7 was introduced. This standarddefines AAC audio that is incompatible with MPEG-1 [2].

There are three different profiles for AAC:

Main profile - includes the full set of coding tools and produces thehighest quality output

Low Complexity (LC) profile - limits some coding tools (TNS) and excludesothers (Prediction and Pre-programming)

Scalable Sample Rate (SSR) Profile - is the least complex of the three,using crippled filter bank

The difference in performance and quality of the Main profile compared to the LC oneis small. However, the encoding and especially the decoding complexity of the MainProfile compared to the LC one are significant [2].

1. Scope

This Vision Document presents general information about the project of the MPEG-2AAC-LC Audio Decoder, describing its purpose, identifying its stakeholders and usersand showing the product through different views, influencing the entire projectdevelopment.

2. Definitions, Acronyms and Abbreviations

This Section describes all definitions for better comprehension about this document.Some definitions can be viewed in the glossary document.

Table 1. Definitions, acronyms and abbreviations.

Term Description

AAC-LC Advanced Audio Coding Low Complexity

SSR Scalable Sample Rate

TNS Temporal Noise-Shaping

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3. Document Structure

This subsection describes what the rest of this document contains and explains howthe document is organized.

Section 2 Project Purpose: this section describes the project purpose, oreither, the product definition and the definition of the problem that theproduct has to solve.

Section 3 Stakeholders and User Description: this section identifies thestakeholders and the users of the product.

Section 4 Product Overview: this section gives a product overview.

Section 5 Other Product Requirements: this section provides a list of thegeneral product requirements.

Section 6 References: this section provides a complete list of alldocuments referenced elsewhere in this document.

2. Project Purpose

The AAC audio coding is an international standard firstly created in MPEG-2 AAC (ISO/IEC 13818-7) [1] and is the base of MPEG-4 general audio coding. MPEG-2 AAC audiocoding has become very popular and been widely used. It is applicable for a widerange of applications from Internet audio over digital audio broadcasting to multi-

channel surround sound. It achieves high compression ratio and high qualityperformance due to an improved time-frequency mapping cooperate with other newtools, like TNS, Predictor, etc. Compared to MPEG-1 Layer 3 (MP3) audio, AACprovides higher quality audio reproduction, yet it requires approximately 50% lessdata. That means music that sounds better, downloads faster, and takes less storagespace or network bandwidth.

A group wants to integrate a competitive AAC-LC IP-Core to its new projects, speciallyin the IP-Brazil Program, could use the proposed IP-Core in this project.

3. Stakeholder and User Descriptions

This section identifies the stakeholders and users of the product, assigningresponsibilities to them. In the following are listed the MPEG-2 AAC-LC Audio Decoderproject stakeholders with their descriptions and responsibilities.

1. Stakeholders

Below are listed the MPEG-2 AAC-LC Audio Decoder project stakeholders with theirdescriptions and responsibilities.

Table 2. Project Stakeholders.

Name Description Responsibilities



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Brazil-IP It is a collaborative effort of Brazilian institutions to createa distributed network of

integrated circuit (IC) designcenters capable of deliveringOCP-IP compliant IntellectualProperty (IP cores).

It gives support to theproject development.

Developers People who develop theproject.

To develop the project.

Computer andElectronicEngineers

People who manage theproject.

They are responsible forsuccessful planning andexecution of the project.

2. UsersTable 3. Product Users.

Name Description Responsibilities

Brazil-IP

projects.

Group responsible for

analyzing and verifying allactivities developed in theproject.

To validate the MPEG-2 AAC-

LC Audio Decoderby testingits functionalities.

3. User Environment

The MPEG-2 AAC-LC Audio Decoderwill be initially developed aiming for both knowingand implementing of the ipProcess [3], a development process for Soft IP-core withprototyping in FPGA. However, the main target of this project is the implementation ofthe corresponding ASIC design.

4. Alternatives and Competition

AAC file is a compressed audio file similar to a .mp3 file, but offers severalperformance improvements [4]; examples include a higher coding efficiency for bothstationary and transient signals, a simpler filter bank, and better handling offrequencies above 16 kHz; maintains quality nearly indistinguishable from the originalaudio source. Moreover, AAC is the default encoding used by Apple iTunes softwareand it is used on the standard of the Brazilian digital television system, also known asISDB-TB, developed by an association including Brazilian Government, Brazilianuniversities and communication companies.

In the market there are many solutions forAAC-LC Audio Decoder, such as AAC-SO1 -

Ultra Low Power AAC Decoder ASIC Core [5]. Your important features are:

All AAC decoding functions implemented at RTL level



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Gate count 75 K gates plus 32K bytes data RAM

Lowest power consumption (clock required 10 MHz)

Single clock synchronous design

Support AAC Low complexity, Main profile and VBR variant Apple iTunesaudio decoding

Straightforward interfaces for SoC applications

Fully synthesizable technology independent of Verilog RTL code

4. Product Overview

Below, it gives a product overview.

1. Product Capabilities

The MPEG-2 AAC-LC Audio Decoder will control all the functionalities and executionof an .acc file in the ADIF format. Such a device will receive an AAC stream,decoding it to the PCM standard audio output format.

2. Product Features

The MPEG-2 AAC-LC Audio Decodermain features are:

MPEG2 AAC Low Complexity (LC) object type data implementation supported

2.0.0.0 Channel Low Complexity MPWG-2 AAC bitstream data input formatsupported

Audio Data Interchange Format (ADIF) input file format, compliant with ISO/IEC 13818-7

16-bit stereo PCM digital audio output format

1. Licensing

The license that will be used is GNU Lesser General Public License (GNU LGPL orsimply LGPL).

2. Deliverables and Installation

The final product will consist of the AAC-LC Decoder (synthesizable Verilog sourcecode), a user guide (which will have all necessary product information to the user),and the test bench of the IP-Core (that can validate IP-Core functionalities).



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Moreover, will be available a presentation about the main features of the AAC-LCDecoder.

3. Assumption, Dependencies and Constraints

Initially, the AAC-LC decoder will play only .aac file extension - a compressed audiofile better than .mp3 file, with several performance improvements.

The project depends a lot of memory storage because of several tasks mustconcurrently be carried out, such as IMDCT (Inverse Modified Discrete CosineTransform) and Window Switching, which require temporary data storage. Hence,such strong memory dependency must be considered in the development of theproject, in order to play the audio file within the time constraint (provided by the44.1 kHz sampling rate). Many methodologies/implementation techniques must be

considered to satisfy such a time constraint.

5. Other Product Requirements

Below it is provided a list of the general product requirements.

4. Applicable Standards

The main standard to be adopted in product development is the MPEG-2 AAC part 7one; in relation to the input file, the adopted standard will be the ADIF file format;regarding the output data, the adopted standard will be the PCM format.

5. Hardware and Environmental Requirements

The environment is composed by:

external RAM memory

FPGA board (not determined your family neither available resources yet)

devices to put in action the system (LCD display, push buttons)

communication interface with an external store device (for input the ADIFformat audio file)

1. Performance Requirements

The needed requirements for the proper functionality of the IP-Core are:

sampling frequency per channel: 44.1 kHz

maximum bit rate per channel: 264.6 kbits/s DDR SDRAM memory interface: maximum data rate at 333Mbits/s (167

MHz)



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flash/SD memory interface: data rate between 20 Mbits/s and 200Mbits/s, depending on the implementation/FPGA board

6. References

[1] ISO-IEC MPEG-2 - Part 7: Audio (ISO 13818-7), 2004

[2] Linneman, R; Advanced Audio Coding on a FPGA , master thesis, Queensland, 2002

[3] IpProcess Methodology, http://www.lincs.org.br/ipprocess/?q=guidelines (Lastaccessed October 14, 2008)

[4] FAAC and FAAD2 AAC software, Audiocoding.com Web Site,http://www.audiocoding.com (Last accessed November 27, 2008)

[5] Silicon Ocean Ultra Low Power AAC Decoder ASIC Core (AAC-SO1), SiliconOcean Inc, http://www.design-reuse.com/sip/view.php? id=15483&backurl=%2Fsip%2Fprovider.php%3Fprov%3D426%26productid%3D15483 (Last accessed November20, 2008)


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Aac Vision Document v1.6