Fifo feedback and control for digital video encoder

Abstract

Method and apparatus for encoding a digital video image stream in an encoder. The encoding includes spatial compression of still images in the digital video image stream and temporal compression between the still images. The spatial compression is carried out by converting a time domain image of a macroblock to a frequency domain image of the macroblock, taking the discrete cosine transform of the frequency domain image, transforming the discrete cosine transformed macroblock image by a quantization factor, and run length encoding the quantized discrete cosine transformed macroblock image. The temporal compression is carried out by reconstructing the run length encoded, quantized, discrete cosine transformed image of the macroblock, searching for a best match macroblock, and constructing a motion vector between them. This forms a bitstream of runlength encoded, quantized, discrete cosine transformed macroblocks and of motion vectors. This bitstream is passed to and through a FIFO buffer to a transmission medium. The number of run length encoded bits is fed back to the encoder for calculation of the quantization factor, to thereby avoid overrunning the buffer and interrupting the transmission.