![]() AAC (Advanced Audio Codec) was standardized as an adjunct to MPEG-2 (as Part 7) before MPEG-4 was issued. MPEG-4 absorbs many of the features of MPEG-1 and MPEG-2 and other related standards, adding new features such as (extended) VRML support for 3D rendering, object-oriented composite files (including audio, video and VRML objects), support for externally-specified Digital Rights Management and various types of interactivity. Uses of MPEG-4 include compression of AV data for web (streaming media) and CD distribution, voice (telephone, videophone) and broadcast television applications. ![]() ![]() 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. MPEG-4 is a collection of methods defining compression of audio and visual (AV) digital data. The codec was first designed to be utilized in H.324 based systems (PSTN and other circuit-switched network videoconferencing and video telephony), 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. The original version of the RealVideo codec was based on H.263 up until the release of RealVideo 8. H.263 has since found many applications on the internet: much Flash Video content (as used on sites such as YouTube, Google Video, MySpace, etc.) is encoded in this format, though many sites now use VP6 encoding, which is supported since Flash 8. Its first version was completed in 1995 and provided a suitable replacement for H.261 at all bitrates. 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. It was developed by the ITU-T Video Coding Experts Group (VCEG) in a project ending in 1995/1996 as one member of the H.26x family of video coding standards in the domain of the ITU-T. H.263 is a video codec standard originally designed as a low-bitrate compressed format for videoconferencing. With some enhancements, MPEG-2 Video and Systems are also used in some HDTV transmission systems. However, it outperforms MPEG-1 at 3 Mbit/s and above. MPEG-2 video is not optimized for low bit-rates, especially less than 1 Mbit/s at standard definition resolutions. The Video section, part 2 of MPEG-2, is similar to the previous MPEG-1 standard, but also provides support for interlaced video, the format used by analog broadcast TV systems. Parts 1 and 2 of MPEG-2 were developed in a joint collaborative team with ITU-T, and they have a respective catalog number in the ITU-T Recommendation Series. MPEG-2 was the second of several standards developed by the Moving Pictures Expert Group (MPEG) and is an international standard (ISO/IEC 13818). As such, TV stations, TV receivers, DVD players, and other equipment are often designed for this standard. It also specifies the format of movies and other programs that are distributed on DVD and similar disks. MPEG-2 is widely used as the format of digital television signals that are broadcasted by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. The format describes also the synchronization and multiplexing of video and audio, some procedures to test the conformance and the reference software. This video codec can only be applied to non-interlaced pictures. Later on, the standard was used for the video cd format VCD. It was the first compression standard for audio and video which was developed by the Moving Picture Experts Group. The coding algorithm uses a hybrid of motion compensated inter-picture prediction and spatial transform coding with scalar quantization, zig-zag scanning and entropy encoding. All subsequent international video coding standards have been based on the H.261 design. H.261 was the first practical digital video coding standard. The algorithm operates at video bit rates between 40 Kbit/s and 2Mbit/s. ISDN lines have data rates which are multiples of 64kbit/s. ![]() It is designed in 1990 for transmission over ISDN lines primarily for video conferences and video telephony. H.261 is a video codec which belongs to the H.26x family of video coding standards in the domain of the ITU-T Video Coding Experts Group (VCEG).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |