A video codec is a combination of two functions: a video encoder and a video decoder. The encoder (also called a compressor) compresses a digitized video bit stream for more efficient storage or transmission. The decoder (also called a decompressor) decompresses the bit stream produced by the encoder to recreate the video sequence. Generally, the algorithm used by a video encoder allows you to specify the tradeoff between the amount of compression and the quality of the recreated video at the output of the decoder.
The video encoder accepts video frames in the form of digital image pixmaps, one at a time. For each input frame, it produces a smaller block of data, called a compressed frame. The decoder receives the compressed frames, one at a time, and recreates the video sequence from these as a series of pixmaps.
In Ultimedia Services, video compression and decompression are supported by encoder and decoder objects. To use one of these objects, an application first calls methods to create and initialize the object. Then, for each frame, it supplies the object with pointers to input data and an output buffer, and it calls a method to compress or decompress the frame.
To learn more about Ultimedia Services video codec objects, see:
For more information on the JPEG International Standard and its technologies, see: Pennebaker, William B., and Joan L. Mitchell. JPEG: Still Image Data Compression Standard. New York: Van Nostrand Reinhold,1993.