[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):

 Replying to [comment:57 Kamedo2]:
 > psymodel.h line 32:
 > {{{
 > #define AAC_CUTOFF(s) (s->bit_rate ?
 FFMIN3(FFMIN3(s->bit_rate/s->channels/2, 3000 + s->bit_rate/s->channels/4,
 12000 + s->bit_rate/s->channels/16), 20000, s->sample_rate / 2):
 (s->sample_rate / 2))
 > }}}
 > The LPF is not applied in VBR now, resulting in noticeably poor quality.

 Try this cutoff:

 {{{
 #define _AAC_CUTOFF(bit_rate,channels,sample_rate) (bit_rate ?
 FFMIN3(FFMIN3( \
     bit_rate/channels, \
     3000 + bit_rate/channels/2, \
     16000 + bit_rate/channels/8), \
     20000, \
     sample_rate / 2): (sample_rate / 2))
 #define AAC_CUTOFF(s) ( \
     (s->flags & CODEC_FLAG_QSCALE) \
     ? _AAC_CUTOFF(s->bit_rate, s->channels, s->sample_rate) \
     : _AAC_CUTOFF((int)(s->bit_rate * (s->global_quality ?
 s->global_quality : 120) / 120.0), 2, s->sample_rate) \
 )
 }}}

 I find it works better, the other was was pretty dull for 64k/ch, which
 ought to be transparent for AAC. This one also works on VBR.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2686#comment:60>
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