[FFmpeg-trac] #2686(avcodec:open): Native AAC encoder collapses at high bitrates on some samples

[FFmpeg]

#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.

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2686#comment:73>
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