Video coding, audio coding and multiplexing | |
SBTVD Standards Structure | |
Native name |
|
---|---|
First published | November 11, 2007 |
Latest version | 0.0 November 11, 2007 |
SBTVD standards | ||||||||||||||||||||
| ||||||||||||||||||||
The audio and video compression aspects of the Brazilian Digital Terrestrial Television Standards are described in the three documents published by ABNT, the Brazilian Association of Technical Standards (Associação Brasileira de Normas Técnicas), the [1] ABNT NBR 15602-1:2007 - Digital terrestrial television - Video coding, audio coding and multiplexing - Part 1: Video coding; ABNT NBR 15602-2:2007 - Digital terrestrial television - Video coding, audio coding and multiplexing - Part 2: Audio coding; and ABNT NBR 15602-3:2007 - Digital terrestrial television - Video coding, audio coding and multiplexing - Part 3: Multiplexing signals.
The standard was written by telecommunications and television experts from many countries with their works coordinated by the SBTVD Forum and cover in detail all the aspects of video and audio coding that applies to SBTVD. The complete document can be found and downloaded freely in English, Spanish and Portuguese at ABNT's website.
The SBTVD Forum is a non-profit organization of private and public companies responsible for the general aspects of Digital TV deployment in Brazil. The organization was founded in 2007 in order to address all technical issues regarding the upcoming SBTVD standard, also known as ISDB-Tb.
Audio and video coding changes are some of the additional technological updates added to the standard. The adoption of Recommendation ITU-T H.264 (MPEG-4 AVC, Advanced Video Coding) as the compression tool allowed for a great leap in quality in all applications: from high definition to low resolution videos. The High Profile is the video compression profile adopted for SDTV and HDTV signals, while the Baseline Profile is used for 1-Seg content. Differently from the Japanese system, the coding level specified for the Brazilian system allows the deliver of low resolution video content of up to 30 frame/s for portable receivers. Audio coding has also seen improvements in the Brazilian specifications. The choice for the MPEG-4 AAC standard combines greater performance and flexibility with low signaling overhead.
The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors of the International Telecommunication Union (ITU); it coordinates standards for telecommunications.
MPEG-4 is a method of defining compression of audio and visual (AV) digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group (MPEG) under the formal standard ISO/IEC 14496 – Coding of audio-visual objects. Uses of MPEG-4 include compression of AV data for web and CD distribution, voice and broadcast television applications.
The first part of this specification stipulates video input format (video signal, signal sample, scanning direction, video-signal parameters), video-coding scheme (a combination of the movement-compensation prediction coding, a block-based transform and a variable-length coding), compression procedures for the video signal and the transmission procedure thereof, signal construction following the coding, and constraints on the coding parameters.
Service | Profile and Level | Resolution | Frame Rate | |
---|---|---|---|---|
HDTV or SD | Fixed and Mobile | HP@L4.0 | 480, 720, 1080 | 30/1,001 and 60/1,001 Hz |
Reduced Resolution | Portable | BP@L1.3 | 160x120, 160x90, 320x240, 320x180, 352x288 | 5, 10, 12, 15, 24 and 30 Hz |
On general terms it can be said that the selected video coding scheme is a H.264 compression with two different profiles, one referring to the fixed high definition and standard definition transmission and the other to portable services. H.264 will be employed in all services; MPEG-2 will not be supported.
MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods, which permit storage and transmission of movies using currently available storage media and transmission bandwidth. While MPEG-2 is not as efficient as newer standards such as H.264/AVC and H.265/HEVC, backwards compatibility with existing hardware and software means it is still widely used, for example in over-the-air digital television broadcasting and in the DVD-Video standard.
Note the error corrections tools of the H.264 baseline profile shall not be used. This was based upon the conclusion that the error resilient tools of H.264 are not effective compared to the applied error-correction coding of the transmission system and therefore the associated cost would have a negative impact on the cost-effectiveness of the portable receivers.
Further, the operating guidelines in the appendix specify the recommended technological conditions for actual operations concerning channel switching time and seamless switching.
Service | Profile and Level | Number of channels | Max. AAC sampling rate | |
---|---|---|---|---|
HDTV or SD | Fixed and Mobile | LC-AAC@L4 HE-AAC v1@L4 | 5 | 48 kHz |
HDTV or SD | Fixed and Mobile | LC-AAC@L2 HE-AAC v1@L2 | 2 | 48 kHz |
Reduced Resolution | Portable | HE-AAC v2@L2 | 2 | 48 kHz |
The audio-coding scheme is a combination of the time-frequency conversion coding scheme and the auditory psychology-weighted bit allocation scheme as defined by MPEG-4 AAC encoding. The second part states the audio input signal, its sampling frequency, number of quantization bits, audio-coding scheme, compression procedures and transmission procedures for the audio. The basic constraints on the audio coding parameters are defined on the table 3.
Advanced Audio Coding (AAC) is an audio coding standard for lossy digital audio compression. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at the same bit rate. The confusingly named AAC+ (HE-AAC) does so only at low bit rates and less so at high ones.
Brazilian system is based on MPEG-4 HE-AAC v2, that is it includes de SBR (spectral band replication) and PS (parametric stereo) tools. Note that, in the High efficiency profile level 4 for one or two channels with SBR present, the maximum AAC sampling rate is 48 kHz. For more than two channels with SBR present, the maximum AAC sampling rate is 24 kHz.
These documents are also officially available at ABNT website.
The audio and video compression requirements established for the Brazilian digital television standards make use of some of the most recent advances in technology available in the television market, maintaining commercial feasibility, and allowing for better picture quality and overall service perception.
The three volumes of the video and audio compression standards can be seen as evolutions suggested for better overall performance levels of the system: ABNT NBR 15602-1:2007 - Digital terrestrial television - Video coding, audio coding and multiplexing - Part 1: Video coding; ABNT NBR 15602-2:2007 - Digital terrestrial television - Video coding, audio coding and multiplexing - Part 2: Audio coding; and ABNT NBR 15602-3:2007 - Digital terrestrial television - Video coding, audio coding and multiplexing - Part 3: Multiplexing signals.
The Moving Picture Experts Group (MPEG) is a working group of authorities that was formed by ISO and IEC to set standards for audio and video compression and transmission. It was established in 1988 by the initiative of Hiroshi Yasuda and Leonardo Chiariglione, group Chair since its inception. The first MPEG meeting was in May 1988 in Ottawa, Canada. As of late 2005, MPEG has grown to include approximately 350 members per meeting from various industries, universities, and research institutions. MPEG's official designation is ISO/IEC JTC 1/SC 29/WG 11 – Coding of moving pictures and audio.
A video codec is an electronic circuit or software that compresses or decompresses digital video. It converts uncompressed video to a compressed format or vice versa. In the context of video compression, "codec" is a concatenation of "encoder" and "decoder"—a device that only compresses is typically called an encoder, and one that only decompresses is a decoder.
MPEG-1 Audio Layer II or MPEG-2 Audio Layer II is a lossy audio compression format defined by ISO/IEC 11172-3 alongside MPEG-1 Audio Layer I and MPEG-1 Audio Layer III (MP3). While MP3 is much more popular for PC and Internet applications, MP2 remains a dominant standard for audio broadcasting.
MPEG-4 Part 3 or MPEG-4 Audio is the third part of the ISO/IEC MPEG-4 international standard developed by Moving Picture Experts Group. It specifies audio coding methods. The first version of ISO/IEC 14496-3 was published in 1999.
DVB-T is an abbreviation for "Digital Video Broadcasting — Terrestrial"; it is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in the UK in 1998. This system transmits compressed digital audio, digital video and other data in an MPEG transport stream, using coded orthogonal frequency-division multiplexing modulation. It is also the format widely used worldwide for Electronic News Gathering for transmission of video and audio from a mobile newsgathering vehicle to a central receive point.
The Integrated Services Digital Broadcasting is a Japanese standard for digital television (DTV) and digital radio used by the country's radio and television networks. ISDB replaced NTSC-J analog television system and the previously used MUSE Hi-vision analogue HDTV system in Japan, and will be replacing NTSC, PAL-M and PAL-N in South America and the Philippines. Digital Terrestrial Television Broadcasting (DTTB) services using ISDB-T started in Japan in December 2003 and in Brazil in December 2007 as a trial. Since then, many countries have adopted ISDB over other digital broadcasting standards.
Advanced Television Systems Committee (ATSC) standards are a set of standards for digital television transmission over terrestrial, cable, and satellite networks. It is largely a replacement for the analog NTSC standard, and like that standard, used mostly in the United States, Mexico and Canada. Other former users of NTSC, like Japan, have not used ATSC during their digital television transition because they adopted their own system called ISDB.
Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting, particularly shortwave, and FM broadcasting. DRM is more spectrally efficient than AM and FM, allowing more stations, at higher quality, into a given amount of bandwidth, using various MPEG-4 audio coding formats.
High-Efficiency Advanced Audio Coding (HE-AAC) is an audio coding format for lossy data compression of digital audio defined as an MPEG-4 Audio profile in ISO/IEC 14496-3. It is an extension of Low Complexity AAC optimized for low-bitrate applications such as streaming audio. HE-AAC version 1 profile uses spectral band replication (SBR) to enhance the compression efficiency in the frequency domain. HE-AAC version 2 profile couples SBR with Parametric Stereo (PS) to enhance the compression efficiency of stereo signals. It is a standardized and improved version of the AACplus codec.
FAAC or Freeware Advanced Audio Coder is a software project which includes the AAC encoder FAAC and decoder FAAD2. It supports MPEG-2 AAC as well as MPEG-4 AAC. It supports several MPEG-4 Audio object types, file formats, multichannel and gapless encoding/decoding and MP4 metadata tags. The encoder and decoder is compatible with standard-compliant audio applications using one or more of these object types and facilities. It also supports Digital Radio Mondiale.
ISDB-T International, ISDB-Tb or SBTVD, short for Sistema Brasileiro de Televisão Digital, is a technical standard for digital television broadcast used in Brazil, Argentina, Peru, Botswana, Chile, Honduras, Venezuela, Ecuador, Costa Rica, Paraguay, Philippines, Bolivia, Nicaragua, El Salvador and Uruguay, based on the Japanese ISDB-T standard. ISDB-T International launched into commercial operation on December 2, 2007, in São Paulo, Brazil, as SBTVD.
ABNT NBR 15601 is the technical standard published by ABNT, the Brazilian Association of Technical Standards, that is responsible for addressing the aspects regarding transmission on the Brazilian Digital Terrestrial Television Standards, also known as SBTVD or ISDB-T version B.
The ABNT NBR 15603 is the technical document of the SBTVD standards that describes in detail aspects regarding Multiplexing and service information (SI). The document is divided in 3 separate parts that covers: SI for digital broadcasting systems ; Data structure and definition of SI basic Information ; and Syntax and definition of SI extended information.
The ABNT NBR 15604 is the document that describes in detail the mandatory and optional functions and features of receivers for the SBTVD. It's essential for the correct implementation by manufacturers of either fixed, mobile or portable receivers aimed at the Brazilian Digital TV market.
The ABNT NBR 15605 is the technical document of the SBTVD standards that describes in detail aspects regarding content security issues and copy protection, also known as Digital Rights Management (DRM). It's a detailed reference for manufacturers and content providers that aim to coordinate transmission and reception protection systems in a transparent and effective way for mass viewing.
ABNT NBR 15606 refers to a collection of technical standards that govern the transmission of digital terrestrial television in Brazil.
The standard ABNT NBR 15607-1:2008 - Digital terrestrial television – Interactivity channel establishes the ways in which a receiver device can send information back to the broadcaster through different communication mechanisms. The transmission of common broadcasting content will be done through the air through the main programming feed, while a more customized use of content can be sent through the interactive channel.
The standard ABNT NBR 15608 describes in further detail the parts of the digital television system that need clarifying, setting directives for implementation in a combination of mandatory and optional features. It can be seen as a refinement of the original specification documents focused on system implementation.