#3859: mp4: start_time never zero
-------------------------------------+-------------------------------------
Reporter: blacktrash | Owner:
Type: defect | Status: new
Priority: normal | Component:
Version: git-master | undetermined
Keywords: | Resolution:
Blocking: | Blocked By:
Analyzed by developer: 0 | Reproduced by developer: 0
-------------------------------------+-------------------------------------
Comment (by blacktrash):
It's a problem with mp4 audio or aac, the duration is too long - I guess
ffmpeg tries to accomodate that by setting a negative start_time when
transcoding and muxing. If I encode the audio separately and mux it in
with -c:a copy start_time is 0, but that only shifts the issue because it
is still longer than the video (or the orginal audio track for that
matter). The values vary depending on the aac library (or native) used,
and sample rate.
{{{
$ ffmpeg -v quiet -i BigBuckBunny_640x360.m4v -vn -c:a copy copy.m4a
$ ffmpeg -v quiet -i BigBuckBunny_640x360.m4v -vn -strict -2 -c:a aac -b:a
64k native.m4a
$ ffmpeg -v quiet -i BigBuckBunny_640x360.m4v -vn -c:a libfdk_aac
-profile:a aac_he -b:a 64k fdk.m4a
$ ffmpeg -v quiet -i BigBuckBunny_640x360.m4v -vn -c:a libfaac -b:a 64k
faac.m4a
$ ffprobe -v quiet -show_entries stream=start_time,duration copy.m4a
[STREAM]
start_time=0.000000
duration=596.474195
[/STREAM]
$ ffprobe -v quiet -show_entries stream=start_time,duration native.m4a
[STREAM]
start_time=-0.023220
duration=596.497415
[/STREAM]
$ ffprobe -v quiet -show_entries stream=start_time,duration faac.m4a
[STREAM]
start_time=-0.023220
duration=596.497415
[/STREAM]
$ ffprobe -v quiet -show_entries stream=start_time,duration fdk.m4a
[STREAM]
start_time=-0.114694
duration=596.588889
[/STREAM]
$ ffprobe -show_entries stream=start_time,duration
BigBuckBunny_640x360.m4v
ffprobe version N-66357-g28dce3c Copyright (c) 2007-2014 the FFmpeg
developers
built on Sep 21 2014 11:24:50 with Apple LLVM version 6.0
(clang-600.0.51) (based on LLVM 3.5svn)
configuration: --enable-gpl --enable-version3 --enable-nonfree
--disable-ffserver --enable-shared --enable-libfdk-aac --enable-libx265
--enable-libx264 --enable-libxvid --enable-libfaac --enable-libmp3lame
--enable-libtheora --enable-libvorbis --enable-libvpx --enable-libvidstab
--extra-cflags=-I/sw/include --extra-libs=-L/sw/lib
libavutil 54. 7.100 / 54. 7.100
libavcodec 56. 1.101 / 56. 1.101
libavformat 56. 4.102 / 56. 4.102
libavdevice 56. 0.100 / 56. 0.100
libavfilter 5. 1.101 / 5. 1.101
libswscale 3. 0.100 / 3. 0.100
libswresample 1. 1.100 / 1. 1.100
libpostproc 53. 0.100 / 53. 0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'BigBuckBunny_640x360.m4v':
Metadata:
major_brand : M4V
minor_version : 1
compatible_brands: M4V M4A mp42isom
creation_time : 2008-06-03 05:23:28
copyright : © 2008 Blender Foundation | www.bigbuckbunny.org
title : Big Buck Bunny
artist : Peach Open Movie Team
composer : Sacha Goedegebure / Ton Roosendaal
date : 2008
Duration: 00:09:56.46, start: 0.000000, bitrate: 1626 kb/s
Stream #0:0(eng): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo,
fltp, 127 kb/s (default)
Metadata:
creation_time : 2008-06-03 05:23:28
handler_name : Apple Sound Media Handler
Stream #0:1(eng): Video: h264 (Constrained Baseline) (avc1 /
0x31637661), yuv420p(tv, smpte170m), 640x360, 1495 kb/s, 24 fps, 24 tbr,
2400 tbn, 4800 tbc (default)
Metadata:
creation_time : 2008-06-03 05:23:28
handler_name : Apple Video Media Handler
[STREAM]
start_time=0.000000
duration=596.474195
[/STREAM]
[STREAM]
start_time=0.000000
duration=596.491667
[/STREAM]
}}}
--
Ticket URL: <https://trac.ffmpeg.org/ticket/3859#comment:13>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
_______________________________________________
FFmpeg-trac mailing list
FFmpeg-trac@avcodec.org
http://avcodec.org/mailman/listinfo/ffmpeg-trac
