[FFmpeg-trac] #2686(avcodec:open): Native AAC encoder collapses at high bitrates on some samples
FFmpeg
trac at avcodec.org
Sun Jul 21 23:43:24 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):
After two days of toying around, the butterworth filter used in psy is
actually counterproductive. Keeping all things equal, lowering the cutoff
actually increases bitrate, if a fixed RD is forced. So, for VBR, it's a
no-no.
I'm trying an FFT-based LP by simply zeroing coeffs, with care at the
boundary to minimize ripple, and it seems to work a lot better, at least
for VBR.
Right now, the implementation is just a POC. It's very dirty. But I'm
getting convinced this is '''the''' way for VBR... and maybe for ABR too.
I'm not sure.
--
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2686#comment:73>
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