[FFmpeg-trac] #10422(undetermined:new): Concatenating raw AAC files directly into MP4 using concat demuxer has wrong duration
FFmpeg
trac at avcodec.org
Sun Jun 18 18:37:05 EEST 2023
#10422: Concatenating raw AAC files directly into MP4 using concat demuxer has
wrong duration
-------------------------------------+-------------------------------------
Reporter: fireattack | Type: defect
Status: new | Priority: normal
Component: | Version:
undetermined | unspecified
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
-------------------------------------+-------------------------------------
Summary of the bug:
I often manually concat segments downloaded from HTTP live streaming (HLS)
locally.
I noticed that if you do so with audio-only raw AAC (ADTS) segments using
concat demuxer, and directly into mp4 container, the output will have
wrong duration.
{{{
ffmpeg -f concat -safe 0 -i chunkindex.txt -c copy 01_directly_concat.m4a
-y
}}}
it will generate a file that has wrong (usually longer) duration in its
metadata.
The following ways will all generate correct file instead:
{{{
ffmpeg -i input.m3u8 -c copy 02_from_m3u8.m4a -y
copy /b 24b4547ddc1a4f528422970016d82c29\*.aac copyb.aac
ffmpeg -i copyb.aac -c copy 03_copyb.m4a -y
del copyb.aac
ffmpeg -f concat -safe 0 -i chunkindex.txt -c copy -f adts - | ffmpeg -i -
-c copy 04_adts_to_m4a.m4a -y
}}}
How to reproduce:
(Removed all the "Estimating duration from bitrate, this may be
inaccurate" to save space)
{{{
>ffmpeg -f concat -safe 0 -i chunkindex.txt -c copy 01_directly_concat.m4a
-y > output_1.txt 2>&1
ffmpeg version 6.0-full_build-www.gyan.dev Copyright (c) 2000-2023 the
FFmpeg developers
built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
configuration: --enable-gpl --enable-version3 --enable-static --disable-
w32threads --disable-autodetect --enable-fontconfig --enable-iconv
--enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma
--enable-libsnappy --enable-zlib --enable-librist --enable-libsrt
--enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray
--enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libdav1d
--enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e
--enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265
--enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl
--enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-
libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-
liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-
amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec
--enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-
libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-
libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-
libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora
--enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-
libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex
--enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite
--enable-libmysofa --enable-librubberband --enable-libsoxr --enable-
chromaprint
libavutil 58. 2.100 / 58. 2.100
libavcodec 60. 3.100 / 60. 3.100
libavformat 60. 3.100 / 60. 3.100
libavdevice 60. 1.100 / 60. 1.100
libavfilter 9. 3.100 / 9. 3.100
libswscale 7. 1.100 / 7. 1.100
libswresample 4. 10.100 / 4. 10.100
libpostproc 57. 1.100 / 57. 1.100
[aac @ 00000175883e44c0] Format aac detected only with low score of 25,
misdetection possible!
[aac @ 00000175883e44c0] Estimating duration from bitrate, this may be
inaccurate (lots of this, removed for clarity)
Input #0, concat, from 'chunkindex.txt':
Duration: N/A, start: 0.000000, bitrate: 99 kb/s
Stream #0:0: Audio: aac (LC), 48000 Hz, stereo, fltp, 99 kb/s
Output #0, ipod, to '01_directly_concat.m4a':
Metadata:
encoder : Lavf60.3.100
Stream #0:0: Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo,
fltp, 99 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
size= 0kB time=00:00:00.00 bitrate=N/A speed=N/A
[ipod @ 00000175883f1740] Non-monotonous DTS in output stream 0:0;
previous: 3532404, current: 3531602; changing to 3532405. This may result
in incorrect timestamps in the output file.
[ipod @ 00000175883f1740] Non-monotonous DTS in output stream 0:0;
previous: 47332408, current: 47331976; changing to 47332409. This may
result in incorrect timestamps in the output file.
size= 14080kB time=00:21:05.63 bitrate= 91.1kbits/s speed=2.53e+03x
[ipod @ 00000175883f1740] Non-monotonous DTS in output stream 0:0;
previous: 119049597, current: 119048794; changing to 119049598. This may
result in incorrect timestamps in the output file.
size= 28928kB time=00:43:12.98 bitrate= 91.4kbits/s speed=2.59e+03x
[ipod @ 00000175883f1740] Non-monotonous DTS in output stream 0:0;
previous: 127887966, current: 127887839; changing to 127887967. This may
result in incorrect timestamps in the output file.
[ipod @ 00000175883f1740] Non-monotonous DTS in output stream 0:0;
previous: 184912256, current: 184910425; changing to 184912257. This may
result in incorrect timestamps in the output file.
[ipod @ 00000175883f1740] Non-monotonous DTS in output stream 0:0;
previous: 184912257, current: 184911449; changing to 184912258. This may
result in incorrect timestamps in the output file.
[ipod @ 00000175883f1740] Non-monotonous DTS in output stream 0:0;
previous: 186374370, current: 186373812; changing to 186374371. This may
result in incorrect timestamps in the output file.
size= 44288kB time=01:06:02.61 bitrate= 91.6kbits/s speed=2.64e+03x
size= 57088kB time=01:25:18.57 bitrate= 91.4kbits/s speed=2.56e+03x
[ipod @ 00000175883f1740] Non-monotonous DTS in output stream 0:0;
previous: 249295288, current: 249294951; changing to 249295289. This may
result in incorrect timestamps in the output file.
size= 65236kB time=01:35:41.53 bitrate= 93.1kbits/s speed=2.47e+03x
video:0kB audio:65976kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: unknown
}}}
Patches should be submitted to the ffmpeg-devel mailing list and not this
bug tracker.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/10422>
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