[FFmpeg-trac] #2686(avcodec:open): Native AAC encoder collapses at high bitrates on some samples
FFmpeg
trac at avcodec.org
Mon Feb 10 06:31:54 CET 2014
#2686: Native AAC encoder collapses at high bitrates on some samples
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Reporter: Kamedo2 | Owner:
Type: defect | Status: open
Priority: normal | Component: avcodec
Version: git-master | Resolution:
Keywords: aac | Blocked By:
regression | Reproduced by developer: 1
Blocking: |
Analyzed by developer: 0 |
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Comment (by klaussfreire):
No, it's not the loudest bin. It's a group of bins. Because the sine isn't
represented on the mdct by a single bin, but rather a ripple pattern that
has to be accurately encoded, or the resulting sine fluctuates in
amplitude (hence the clipping).
But I got a solution. I'm doing the listening tests now, but it sounds
good. Basically, a two-front approach: lower the volume of near-clipping
windows (and only those, to make it idempotent), and tweak tonal band
priorization (because the sine wave was getting too few bits after all).
--
Ticket URL: <https://trac.ffmpeg.org/ticket/2686#comment:243>
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