[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
-------------------------------------+-------------------------------------
             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 Kamedo2):

 [[Image(http://i44.tinypic.com/1zmczg5.png)]]
 aaccoder.c line 806 from
 {{{
                 ? (refbits * 1.6f * avctx->sample_rate / 1024)
 }}}
 to
 {{{
                 ? (refbits * 2.5f * avctx->sample_rate / 1024)
 }}}
 raises the LPF and the sound is much clearer(at the cost of more noise,
 but it's certainly better per real bitrate).
 I feel the sound is bad in only tonal part of the music in VBR. And this
 encoder uses fewer bits, sometimes nearly half less, for the tonal part,
 unlike Opus, which has a distinctive tonality boost function.

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2686#comment:118>
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