[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 Kamedo2):

 Replying to [comment:184 klaussfreire]:
 > Do you have an example? Could you describe in that example what you feel
 is inferior compared to abr?
 In tonal part of the music, the vbr suffers from lower S/N ratio and more
 LPF effect, because the cutoff frequency is lower. 96kbps vs -q:a 0.52 is
 more pronounced.

 > Also, do you perhaps have something that results in abnormally large
 bitrates in your std calibration sample? That could be forcing you to pick
 a lower q to match the 128k average, and thus decrease overall quality. I
 did fix a few of those in v6, but maybe there's some left, or maybe it has
 to be further constrained.
 No, the std calibration sample is from CDs, and it lacks speech samples. I
 tried these:
 http://www.rarewares.org/test_samples/
 and death2, KMFDM-Dogma, male_speech was particularly high in -q:a 0.7
 (128kbps), more than 200kbps. Male speech have more bitrates than the
 female one.

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2686#comment:186>
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