DCT-Q-IDCT

The DCT-Q-IDCT VirtualDub filter performs the folowing steps: color subsampling, blockwise forward DCT, matrix based quantization, source coding, inverse-DCT (IDCT), color upsampling. There is done a compression and decompression as in intraframe MPEG2 (I-Frames).

You can use different quantization matrices and immediately see the effects on your video. Also you can check if your other filters in the chain improves the compression-ratio for a fixed quality (quantizer stepsize). It creates a compatible MPEG2 video sequence consisting of a single I-frame which can be saved in a file.

Also statistical data about the input video is collected and a histogram can be created. This histogram shoes the distribution for each coefficient of the dct-transformed macroblocks, of the frames, which have been displayed.