Citizendia
Your Ad Here

H. 263 is a video codec standard originally designed by the ITU-T in a project ending in 1995/1996 as a low-bitrate compressed format for videoconferencing. A video Codec is a device or Software that enables Video compression and/or decompression for digital video The ITU Telecommunication Standardization Sector ( ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication A videoconference (also known as a videoteleconference) is a set of interactive Telecommunication technologies which allow two or more locations to interact It is one member of the H. 26x family of video coding standards in the domain of the ITU-T Video Coding Experts Group (VCEG). The Video Coding Experts Group or VCEG is the informal name of Question 6 (Video coding of Working Party 3 (Media coding of Study Group 16 (Multimedia terminals systems

The codec was first designed to be utilized in H.324 based systems (PSTN and other circuit-switched network videoconferencing and videotelephony), but has since also found use in H.323 (RTP/IP-based videoconferencing), H.320 (ISDN-based videoconferencing), RTSP (streaming media) and SIP (Internet conferencing) solutions. H324 is an ITU-T recommendation for voice, Video and Data transmission over regular analog Phone lines The public switched telephone network ( PSTN) is the network of the world's public circuit-switched Telephone networks in much the same way that the In Telecommunications a circuit switching network is one that establishes a fixed bandwidth circuit (or channel) between nodes and terminals H323 is an umbrella Recommendation from the ITU Telecommunication Standardization Sector (ITU-T that defines the protocols to provide Audio-visual communication The Real-time Transport Protocol (or RTP) defines a standardized packet format for delivering audio and video over the Internet H320 is an umbrella recommendation by the ITU-T for running Multimedia (Audio/Video/Data over ISDN based networks The Real Time Streaming Protocol ( RTSP) developed by the IETF and created in 1998 as RFC 2326 is a protocol for use in Streaming media Streaming multimedia is Multimedia that is constantly received by and normally presented to an end-user while it is being delivered by a streaming provider (the The Session Initiation Protocol ( SIP) is a signalling protocol widely used for setting up and tearing down Multimedia Communication sessions

H. 263 was developed as an evolutionary improvement based on experience from H.261, the previous ITU-T standard for video compression, and the MPEG-1 and MPEG-2 standards. H261 is a 1990 ITU-T video coding standard originally designed for transmission over ISDN lines on which data rates are multiples of 64 kbit/s MPEG-1 was an early Standard for Lossy compression of Video and audio. MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information" Its first version was completed in 1995 and provided a suitable replacement for H.261 at all bitrates. H261 is a 1990 ITU-T video coding standard originally designed for transmission over ISDN lines on which data rates are multiples of 64 kbit/s It was further enhanced in projects known as H. 263v2 (also known as H. 263+ or H. 263 1998) and H. 263v3 (also known as H. 263++ or H. 263 2000).

The next enhanced codec developed by ITU-T VCEG (in partnership with MPEG) after H. The Video Coding Experts Group or VCEG is the informal name of Question 6 (Video coding of Working Party 3 (Media coding of Study Group 16 (Multimedia terminals systems The Moving Picture Experts Group, commonly referred to as simply MPEG, is a Working group of ISO / IEC charged with the development of video and 263 is the H.264 standard, also known as AVC and MPEG-4 part 10. H264 is a standard for Video compression. It is also known as MPEG-4 Part 10, or MPEG-4 AVC (for Advanced Video Coding) MPEG-4 is a collection of methods defining compression of audio and visual (AV digital data As H. 264 provides a significant improvement in capability beyond H. 263, the H. 263 standard is now considered primarily a legacy design (although this is a recent development). Most new videoconferencing products now include H. 264 as well as H. 263 and H. 261 capabilities.

Contents

Versions

Since the original ratification of H. 263 in March 1996 (approving a document that was produced in November 1995), there have been two subsequent additions which improved on the original codec by additional optional annexes (extensions). For example, the H. 263v2 added a deblocking filter via Annex J.

The original H. 263 specified the following annexes:

In March of 1997, an informative Annex I describing Error Tracking — an encoding technique for providing improved robustness to data losses and errors, was approved to provide information for the aid of implementers having an interest in such techniques.

H. 263v2 (H. 263+)

H. 263v2 (also known as H. 263+ or as the 1998 version of H. 263) is the informal name of the second edition of the ITU-T H. 263 international video coding standard. It retained the entire technical content of the original version of the standard, but enhanced H. 263 capabilities by adding several annexes which can substantially improve encoding efficiency and provide other capabilities (such as enhanced robustness against data loss in the transmission channel). The H. 263+ project was ratified by the ITU in February 1998. It added the following Annexes:

H. A deblocking filter is applied to blocks in decoded video to improve visual quality and prediction performance by smoothing the sharp edges which can form between blocks when block 263v2 also added support for flexible customized picture formats and custom picture clock frequencies. Previously the only picture formats supported in H. 263 had been Sub-QCIF, QCIF, CIF, 4CIF, and 16CIF, and the only picture clock frequency had been 30000/1001 (approximately 29. CIF ( Common Intermediate Format) also known as FCIF ( Full Common Intermediate Format) is a format used to standardize the horizontal and vertical 97) clock ticks per second.

H. 263v2 specified a set of recommended modes in an informative appendix (Appendix II, since deprecated):

Level 1 Level 2 Level 3
Advanced INTRA Coding Yes Yes Yes
Deblocking Filter Yes Yes Yes
Supplemental Enhancement Information (Full-Frame Freeze Only) Yes Yes Yes
Modified Quantization Yes Yes Yes
Unrestricted Motion Vectors No Yes Yes
Slice Structured Mode No Yes Yes
Reference Picture Resampling (Implicit Factor-of-4 Mode Only) No Yes Yes
Advanced Prediction No No Yes
Improved PB-frames No No Yes
Independent Segment Decoding No No Yes
Alternate INTER VLC No No Yes
Level 1 Level 2 Level 3

H. 263v3 (H. 263++) and Annex X

The definition of H. 263v3 (also known as H. 263++ or as the 2000 version of H. 263) consisted of the addition of three additional annexes. These annexes and an additional annex that specified profiles (approved the following year) were originally published as separate documents from the main body of the standard itself. The additional annexes specified are:

The prior informative Appendix II (recommended optional enhancement) was obsoleted by the creation of the normative Annex X.

In June 2001, another informative appendix (Appendix III, Examples for H. 263 encoder/decoder implementations) was approved. It describes techniques for encoding and for error/loss concealment by decoders.

In January 2005, a unified H. 263 specification document was produced (with the exception of Appendix III, which remains as a separately-published document).

In August 2005, an implementors guide was approved to correct a small error in the seldom-used Annex Q reduced-resolution update mode.

Applications

External links

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
 Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic