What is an audio or video data container
A container is a file format or data stream that encodes data in one way or another.
A codec is an encoder and decoder. Something that transforms the data. In the case of media, codecs are designed to compress the data stream and are often lossy.
Within the DV formats, the container can be AVI, Quicktime or the lesser known MXF. The codecs within these containers and formats may be different.
If we are talking about video compression, then there is a general rule of thumb: the more advanced the media we encode, the smaller the data stream or the file size, but more resources will be required for playback with subjectively equal recording quality.
Codec development took place in parallel with the growth of computer performance.
In 1988 the H.261 codec appeared. Few have heard of it, although it was in it that the concepts of keyframes, block vector transforms, and other technologies appeared, which are now used in all popular codecs.
That is, the video is not stored as a sequence of frames, as in a movie. The video is analyzed by the encoder, which finds an abrupt change in the image, for example the beginning of a new scene, and saves that frame, which is called the reference frame. And until the next keyframe, describe only the changes in this frame over time, dividing the image into blocks.
A group of MPEG-1 compression standards has been developed in the 93rd Moving Images Expert Group (MPEG), formed by the International Organization for Standardization (ISO).
With respect to H.261, it was possible to construct changes not only from the previous frame of reference, but also from the next one; and also to encode some section isolated from the rest.
In 1996 MPEG-2 appeared. It is for them that DVDs will be encoded later, you can imagine the scale of distribution. Interlaced scanning is back in the game, so there is nothing radically new.
It is necessary to dwell on the DVD video in detail. These discs appeared in the distant 96, and by 2003 they had become the leading consumer video format.
Movies were recorded at 720 × 576 pixels, which is the same as the D1 format. At the same time, compression made it possible to reduce the bit rate, that is, the data stream, to 9.8 Mbps, which made it possible to write movies on 4.7 GB discs. Coding format: 4: 2: 0, with decreased resolution of the chrominance channels; This trick allows you to reduce the size of the files without significantly affecting the quality of the image, because the luminance channel remains at the original resolution.
The third MPEG does not exist separately, all its chips were absorbed by the second. It also has nothing to do with mp3. They started developing it roughly on par with the second, aiming for higher bit rates, but then they solved all their tasks within the MPEG2 framework.
