QuickTime 4 Reference

About Image Transcoding

Transcoding has two distinct advantages over the decompress-then-recompress approach to converting the format of compressed data. The first advantage is that the operation is usually substantially faster, since much of the data can be copied directly from the source image data format to the destination image data format. The second advantage is that the operation is usually more accurate because decompressing and recompressing provides two steps for introducing rounding and quantization errors. By directly transcoding, opportunities for small errors are substantially reduced.

Image Transcoding Support