#5162: aac encoder adds extra frame(s)
---------------------------------+--------------------------------------
Reporter: slhck | Type: defect
Status: new | Priority: normal
Component: avcodec | Version: git-master
Keywords: aac | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
---------------------------------+--------------------------------------
Summary of the bug: The aac encoder adds one extra audio frame when
encoding
How to reproduce:
{{{
ffmpeg -i out.mp4 -c:v copy -c:a aac out2.mp4
ffmpeg version N-78077-g5989add-tessus Copyright (c) 2000-2016 the FFmpeg
developers
built with Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM
3.5svn)
configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg --as=yasm
--extra-version=tessus --enable-avisynth --enable-fontconfig --enable-gpl
--enable-libass --enable-libbluray --enable-libfreetype --enable-libgsm
--enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb
--enable-libopencore-amrwb --enable-libopus --enable-libschroedinger
--enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvidstab
--enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-
libvpx --enable-libwavpack --enable-libx264 --enable-libx265 --enable-
libxavs --enable-libxvid --enable-libzmq --enable-version3 --disable-
ffplay --disable-indev=qtkit --disable-indev=x11grab_xcb
libavutil 55. 13.100 / 55. 13.100
libavcodec 57. 22.100 / 57. 22.100
libavformat 57. 21.101 / 57. 21.101
%
!3491
libavdevice 57. 0.100 / 57. 0.100
libavfilter 6. 25.100 / 6. 25.100
libswscale 4. 0.100 / 4. 0.100
libswresample 2. 0.101 / 2. 0.101
libpostproc 54. 0.100 / 54. 0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'out.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf56.40.101
Duration: 00:12:53.97, start: 0.000000, bitrate: 2180 kb/s
Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p,
1920x1080, 1857 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
Metadata:
handler_name : VideoHandler
Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz,
stereo, fltp, 317 kb/s (default)
Metadata:
handler_name : SoundHandler
[mp4 @ 0x7f8f8b842a00] Codec for stream 0 does not use global headers but
container format requires global headers
Output #0, mp4, to 'out2.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf57.21.101
Stream #0:0(eng): Video: h264 ([33][0][0][0] / 0x0021), yuv420p,
1920x1080, q=2-31, 1857 kb/s, 25 fps, 25 tbr, 12800 tbn, 12800 tbc
(default)
Metadata:
handler_name : VideoHandler
Stream #0:1(eng): Audio: aac (LC) ([64][0][0][0] / 0x0040), 48000 Hz,
stereo, fltp, 128 kb/s (default)
Metadata:
handler_name : SoundHandler
encoder : Lavc57.22.100 aac
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
frame=19348 fps=353 q=-1.0 Lsize= 188726kB time=00:12:53.97
bitrate=1997.5kbits/s speed=14.1x
video:175481kB audio:12669kB subtitle:0kB other streams:0kB global
headers:0kB muxing overhead: 0.306213%
[aac @ 0x7f8f8b806600] Qavg: 691.497
}}}
The input file:
{{{
ffprobe -i out.mp4 -show_streams | grep nb_frames
…
nb_frames=36280
}}}
The output file has one extra (audio) frame:
{{{
ffprobe -i out2.mp4 -show_streams | grep nb_frames
…
nb_frames=36281
}}}
This means that if you re-encode a file multiple times, audio and video
will become more and more asynchronous.
The same bug affects libfdk_aac as well, although it adds two frames. When
I add `-shortest`, I get one frame ''less'' than the original file.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/5162>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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