[FFmpeg-trac] #2686(avcodec:open): Native AAC encoder collapses at high bitrates on some samples
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Mon Jul 22 08:40:30 CEST 2013
#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):
Alright, i'm attaching a new VBR patch. CBR/ABR shouldn't have changed
(shouldn't, but might). I will probably want to apply the same logic to
CBR/ABR as well, since it works very well (ie: cutoff not with a filter
but with the bit allocator, stop spending bits on HF if we're starving for
bits).
A heads-up: VBR's q-to-kbps curve has changed, and there's some artifacts
that sound like scratchy noises (especially audible in the sine sample),
that are due to clipping. I think it's not specific to this patch, but I
just noticed it. I'm not sure how to attack it. Normally, I'd apply
compression on the IMDCT stage, but since that's on the decoder side, I'll
probably have to find a clever way to predict clipping on the encoder and
compensate. Craptastic.
Anyway, I do think VBR has been greatly improved on this patch. Let me
know what you think.
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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2686#comment:78>
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