[FFmpeg-devel] [PATCH] G.722 trellis encoder

Martin Storsjö martin
Thu Sep 23 23:43:41 CEST 2010


As in $subj, this adds a G.722 encoder codepath that uses trellis to 
improve the quality.

For the lower sub-band, it tries a few other values around the one 
suggested by encode_low. Since the lowest 2 bits of the codeword for the 
lower subband doesn't affect the predictor, testing values that don't 
change the lowest 2 bits is useless, since it's less optimal for the 
current sample but still affect the predictor in the same way.

For the higher sub-band, there's only 4 different combinations, so instead 
of testing a range around the value suggested by encode_high, it tests all 
4 of them. (This gives a much larger gain than testing more values in the 
lower sub-band.)

For one sample, using -trellis 5, the stddev is lowered from 76.49 to 
62.10 and the PSNR is increased from 58.66 to 60.47.

// Martin
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