[FFmpeg-trac] #2686(FFmpeg:new): Native AAC encoder collapses at high bitrates on some samples
FFmpeg
trac at avcodec.org
Tue Jun 18 20:08:57 CEST 2013
#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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