Video Codecs!
MPEG-4 part 10/H.264/AVC
MPEG-4 part 10 is a standard technically aligned with the ITU-T.s H.264 and often also referred to as AVC. This new standard is the current state of the art of ITU-T and MPEG standardized compression technology, and it is rapidly gaining adoption into a wide variety of applications. It uses different profiles and levels to identify different configurations and uses. It contains a number of significant advances in compression capability, and it has recently been adopted into a number of company products, including the Xbox 360, PlayStation Portable, iPod, the Nero Digital product suite, and Mac OS X 10.4, as well as high-definition Blu-ray Disc. Though it has impressive quality at bit rates lower than older codecs like MPEG-2, it is very processor-intensive to edit, encode, and play back, and older computers or low-powered portable devices may have difficulty playing it back or may drain their batteries faster than normal when using it.
VP6
This is a proprietary video codec developed by On2 Technologies and used in Adobe Flash Player 8 and newer.
VC-1
This is an SMPTE standardized video compression standard (SMPTE 421M) based on Microsoft.s WMV 9 video codec. It is also one of the three mandatory video codecs in Blu-ray high-definition optical disc standards (MPEG-2 and H.264 are the others). It is commonly found on the Web, in portable devices, and on computers that support the WMV format. Like MPEG-4 part 10, VC-1 uses the concept of profiles to differentiate different uses and data settings it will support though its configurations are more straightforward than MPEG-4 part 10/AVC/H.264.
MPEG-2 part 2
Used on DVD, on SVCD, and in most digital video broadcasting and cable distribution systems, MPEG-2.s sweet spot in the market is the quality of video it provides for standard-definition video. When used on a standard DVD, it offers good picture quality and supports wide-screen. In terms of technical design, the most significant enhancement in MPEG-2 over its predecessor, MPEG-1 (see the next section), was the addition of support for interlaced video. MPEG-2 is now considered an aged codec, but it has tremendous market acceptance and a very large installed base, and even the relatively new high-definition video acquisition format, HDV, is based on MPEG-2. Its use will decline as a delivery format as more efficient codecs such as AVC and VC-1 are adopted for HD video.
H.261
Used primarily in older videoconferencing and video telephony products, H.261, developed by the ITU-T, was the first practical digital video compression standard. Essentially all subsequent standard video codec designs are based on it. It included such well-established concepts as YCbCr color representation, the 4:2:0 sampling format, 8-bit sample precision, 16 by 16 macroblocks, block-wise motion compensation, 8 by 8 block-wise discrete cosine transformation, zigzag coefficient scanning, scalar quantization, run+value symbol mapping, and variable length coding. H.261 supported only progressive scan video.
DV
The DV codec, in terms of file-based content (as opposed to tape), has two main versions: DV-NTSC, the 720 by 480-pixel default DV codec comes installed with QuickTime for use in accordance with the North American broadcast standard and 720 by 576 DV-PAL is also available for European playback standards.
LOSSY VS. LOSSLESS
Lossless compression recreates a compressed file as an identical match to its original form. All lossless compression uses techniques to break up a file into segments for storage or transmission that gets reassembled later. Lossless compression is used for files, such as applications, that need to be reproduced exactly like the original file. Lossy compression, on the other hand, eliminates repeated or “unnecessary” pieces of data. When a file is decompressed, you get the compression software’s reinterpretation of the original file. Lossy compression can’t be used to compress anything that needs to be reproduced exactly.
