[FFmpeg-trac] #7257(undetermined:new): concatenating MP4 files reads all of them twice
FFmpeg
trac at avcodec.org
Wed Jun 13 15:16:15 EEST 2018
#7257: concatenating MP4 files reads all of them twice
-------------------------------------+-------------------------------------
Reporter: AyrA | Type: defect
Status: new | Priority: normal
Component: | Version: git-
undetermined | master
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
-------------------------------------+-------------------------------------
== Summary of the bug ==
When concatenating multiple mp4 files using {{{-f concat}}} each input
file is read twice but only on the second pass the file is actually
processed. This problem does not seem to be present for other formats like
AVI or MKV.
The generated output file looks as expected and works.
== How to reproduce ==
Command: {{{ffmpeg -f concat -safe 0 -i list.txt -c copy -strict
experimental output.mp4}}}
list.txt: File with at least one mp4 file in it
== Other Info ==
* My device runs Microsoft Windows 7 x64 (6.1.7601)
* The first seemingly useless pass is slower than the second actual pass
but CPU utilization stays almost at 0 during the entire time of the first
pass (Unbuffered IO or seeking weirdly?)
* First pass is performed after 51 frames have been written to the output
according to the console status line
* This behavior is only present when using {{{-f concat}}} and not when
processing a single file
* Each mp4 input file is processed twice
* The concat text file can contain different container (mixed mkv and mp4
for example) and only the MP4 files are processed twice
* The issue is present regardless of file location (Tested: local disk and
SMB share)
* This issue almost doubles encoding time
== Version Info ==
{{{
ffmpeg version N-91266-g8c20ea8ee0 Copyright (c) 2000-2018 the FFmpeg
developers
built with gcc 7.3.0 (GCC)
configuration: --disable-static --enable-shared --enable-gpl --enable-
version3
--enable-sdl2 --enable-bzlib --enable-fontconfig --enable-gnutls --enable-
iconv
--enable-libass --enable-libbluray --enable-libfreetype --enable-
libmp3lame
--enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg
--enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr
--enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack
--enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2
--enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-
libvidstab
--enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-
libspeex
--enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-
ffnvcodec
--enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-
dxva2
--enable-avisynth
libavutil 56. 18.102 / 56. 18.102
libavcodec 58. 20.101 / 58. 20.101
libavformat 58. 17.100 / 58. 17.100
libavdevice 58. 4.100 / 58. 4.100
libavfilter 7. 25.100 / 7. 25.100
libswscale 5. 2.100 / 5. 2.100
libswresample 3. 2.100 / 3. 2.100
libpostproc 55. 2.100 / 55. 2.100
}}}
--
Ticket URL: <https://trac.ffmpeg.org/ticket/7257>
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