Efficient coding of DCT coefficients by joint position-dependent encoding

In a typical MC-DCT encoding scheme, a large portion of the bit rate is used to encode the location and amplitude information of the nonzero quantized DCT coefficients. Therefore efficient encoding of the DCT coefficients is extremely important. We describe the joint position-dependent encoding (PDE) approach to encode the DCT coefficients. Joint PDE exploits the variations in statistical properties of the runlengths and amplitudes as a function of position by introducing a set of 2-D codebooks in which each quantized DCT coefficient is assigned to one codebook in the set based on its location. Utilizing an MPEG-2 codec, we compare the bit rates using the joint PDE variable length codes (VLCs) with the bit rates produced by the MPEG-2 VLCs. We also examine how performance is affected by the number of codebooks.