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

FFmpeg trac at avcodec.org
Sat Jul 20 21:02:21 CEST 2013


#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            |
-------------------------------------+-------------------------------------

Comment (by Kamedo2):

 Replying to [comment:60 klaussfreire]:
 > 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 tried, but isn't this cutoff strange? It sounds like the lowpass is
 always 20kHz.
 The problem of ffmpeg_aacvbr_pulse1.flac is solved by this.

 I'm using current git head 54813 + aac-improvements-
 wip-v2-rclookahead.2.patch + aacpsy.c Line 308
 {{{
 pctx->frame_bits   = FFMIN(2560, chan_bitrate * AAC_BLOCK_SIZE_LONG /
 ctx->avctx->sample_rate);
 }}}

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2686#comment:61>
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