The same palette is used for a run of length between one and 32 blocks. To select one of the four entries, 2 bits per pixel are written to the bit-stream. In four color mode, each pixel in a block is decoded as one of four colors which are specified in a palette. This can be interpreted as a palette with a single color. In single color mode, all pixels in a block are decoded in the same color. Runs of skip blocks are coded in a run-length encoding scheme, enabling a high compression ratio in static areas of the picture. If a block is coded in skip mode, the content of the block at same location in the previous frame is copied to the current frame. The skip mode realizes conditional replenishment. As a tradeoff, the compression performance of Apple Video is lower. Because Apple Video operates in the image domain without motion compensation, decoding is much faster than MPEG-style codecs which use motion compensation and perform coding in a transform domain. Colors are represented by 16 bits with a bit-depth of 5 bit for each of the three components red, green, and blue, a format known as RGB555. Each block is coded in one of four coding modes: skip, single color, four color, or 16 color. Each frame is segmented into 4×4 blocks in raster-scan order. The codec operates on 4×4 blocks of pixels in the RGB colorspace.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |