[FFmpeg-devel] [PATCH] adpcm: Use a hash table to improve chcking for duplicate samples
Martin Storsjö
martin
Thu Nov 18 22:19:04 CET 2010
Hi,
With the attached patch #1, the runtime for -trellis 8 drops from 158 to
21 seconds, for my 30 second sample, see
http://albin.abo.fi/~mstorsjo/adpcm-graphs3/hash.pdf for details on that,
compared to the current trunk and compared to the old original code. This
speeds up things enough to actually be able to run all the way to -trellis
15 within reasonable time (running into the issue with ssd wrapping
around, as I sent a patch for earlier), and one notices that it exhausts
all testable combinations at around -trellis 10, where the PSNR doesn't
really increase any longer.
As discussed earlier, the skipping when a matching sample is found could
also be done only if the ssd actually is worse than for that one.
Curiously enough, it gives slightly worse results (and slows things down
quite a bit), see
http://albin.abo.fi/~mstorsjo/adpcm-graphs3/with_without_check.pdf.
The second patch gives a slight, 0.1 dB increase in PSNR.
// Martin
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