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

[FFmpeg]

#2686: Native AAC encoder collapses at high bitrates on some samples
-------------------------------------+-------------------------------------
             Reporter:  Kamedo2      |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  FFmpeg       |                  Version:  1.0.7
             Keywords:  native aac   |               Blocked By:
  encoder sound quality 256kbps      |  Reproduced by developer:  0
  320kbps                            |
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 '''Summary of the bug:'''
 FFmpeg native aac encoder outputs horrible sound around 256kbps or more on
 particular samples. It happens at '''higher''' bitrates. The quality
 degrades as I '''increase''' the bitrates, and become most degraded at
 320-400kbps.


 '''How to reproduce:'''
 {{{
 ffmpeg -i ffmpeg_aac320k_collapse.flac -vn -c:a aac -strict experimental
 -b:a 320k ffmpeg_aac320k_collapse.mp4
 }}}
 I couldn't reproduce the results when I trimmed the most problematic
 sample down to 8 seconds, but by adding 10 seconds of silence before the
 sample, the bug could be reproduced. So I'm going to upload the sample
 with 10 seconds of silence attached. The native aac encoder was ok on many
 music clips at 320kbps, and only some clips exhibit noticeably bad quality
 aac files, to an extent I'd call it 'bug'.

 '''Console Output:'''
 {{{
 ffmpeg version N-54096-ge41bf19 Copyright (c) 2000-2013 the FFmpeg
 developers
   built on Jun 19 2013 00:20:06 with gcc 4.8.1 (GCC)
   configuration: --enable-gpl --enable-version3 --enable-libmp3lame
 --enable-lib
 vorbis --enable-nonfree --enable-libfdk-aac --enable-libvo_aacenc
 --enable-libfa
 ac --extra-ldflags=-static --extra-cflags='-march=nocona -mfpmath=sse'
 --optflag
 s=-O2
   libavutil      52. 37.101 / 52. 37.101
   libavcodec     55. 16.100 / 55. 16.100
   libavformat    55.  9.100 / 55.  9.100
   libavdevice    55.  2.100 / 55.  2.100
   libavfilter     3. 77.101 /  3. 77.101
   libswscale      2.  3.100 /  2.  3.100
   libswresample   0. 17.102 /  0. 17.102
   libpostproc    52.  3.100 / 52.  3.100
 [flac @ 0003f160] max_analyze_duration 5000000 reached at 5015510
 microseconds
 Input #0, flac, from '05-true_my_heart_2m50s.flac':
   Duration: 00:00:18.01, bitrate: 573 kb/s
     Stream #0:0: Audio: flac, 44100 Hz, stereo, s16
 Output #0, mp4, to '05-true_my_heart_2m50s_320k.mp4':
   Metadata:
     encoder         : Lavf55.9.100
     Stream #0:0: Audio: aac ([64][0][0][0] / 0x0040), 44100 Hz, stereo,
 fltp, 32
 0 kb/s
 Stream mapping:
   Stream #0:0 -> #0:0 (flac -> aac)
 Press [q] to stop, [?] for help
 size=     331kB time=00:00:18.01 bitrate= 150.4kbits/s
 video:0kB audio:327kB subtitle:0 global headers:0kB muxing overhead
 1.151111%
 }}}

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