[FFmpeg-trac] #2938(undetermined:new): Incorrect start time and duration when transcoding audio-only (-vn) from A/V files.
FFmpeg
trac at avcodec.org
Fri Sep 6 00:10:05 CEST 2013
#2938: Incorrect start time and duration when transcoding audio-only (-vn) from
A/V files.
-------------------------------------+-------------------------------------
Reporter: rlabonte | 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 rlabonte):
Replying to [comment:1 cehoyos]:
> Replying to [ticket:2938 rlabonte]:
> > Muxing to matroska or raw AAC results in a 0.00 start time, but the
duration is still off by 40ms.
>
> Does this mean audio gets significantly longer (or shorter?) if you
encode several times?
I ran the same command as above but muxed to an MKV container.
FFprobe output from MKV output of the same command as before:
{{{
% ffprobe offset.mkv -show_streams -show_format
ffprobe version N-56052-g59b9ecc Copyright (c) 2007-2013 the FFmpeg
developers
built on Sep 5 2013 14:16:47 with gcc 4.4.3 (Ubuntu 4.4.3-4ubuntu5.1)
configuration: --enable-nonfree --enable-gpl --enable-version3 --enable-
libvpx --enable-libtheora --enable-libvorbis --enable-libfaac --enable-
libfdk_aac --enable-libx264 --enable-libfreetype
libavutil 52. 43.100 / 52. 43.100
libavcodec 55. 31.101 / 55. 31.101
libavformat 55. 16.101 / 55. 16.101
libavdevice 55. 3.100 / 55. 3.100
libavfilter 3. 83.102 / 3. 83.102
libswscale 2. 5.100 / 2. 5.100
libswresample 0. 17.103 / 0. 17.103
libpostproc 52. 3.100 / 52. 3.100
Input #0, matroska,webm, from 'offset.mkv':
Metadata:
MAJOR_BRAND : qt
MINOR_VERSION : 537199360
COMPATIBLE_BRANDS: qt
TIMECODE : 00:00:00:00
ENCODER : Lavf55.16.101
Duration: 00:09:56.50, start: 0.000000, bitrate: 130 kb/s
Stream #0:0(eng): Audio: aac, 48000 Hz, 5.1, fltp (default)
Metadata:
CREATION_TIME : 2008-05-27 18:32:32
LANGUAGE : eng
HANDLER_NAME : Apple Alias Data Handler
[STREAM]
index=0
codec_name=aac
codec_long_name=AAC (Advanced Audio Coding)
profile=unknown
codec_type=audio
codec_time_base=1/48000
codec_tag_string=[0][0][0][0]
codec_tag=0x0000
sample_fmt=fltp
sample_rate=48000
channels=6
bits_per_sample=0
id=N/A
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/1000
start_pts=0
start_time=0.000000
duration_ts=N/A
duration=N/A
bit_rate=N/A
nb_frames=N/A
nb_read_frames=N/A
nb_read_packets=N/A
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
TAG:CREATION_TIME=2008-05-27 18:32:32
TAG:LANGUAGE=eng
TAG:HANDLER_NAME=Apple Alias Data Handler
[/STREAM]
[FORMAT]
filename=offset.mkv
nb_streams=1
nb_programs=0
format_name=matroska,webm
format_long_name=Matroska / WebM
start_time=0.000000
duration=596.501000
size=9757210
bit_rate=130859
probe_score=100
TAG:MAJOR_BRAND=qt
TAG:MINOR_VERSION=537199360
TAG:COMPATIBLE_BRANDS=qt
TAG:TIMECODE=00:00:00:00
TAG:ENCODER=Lavf55.16.101
[/FORMAT]
}}}
I previously failed to mention, -c:a copy is unaffected by this bug. I
did a -c:a copy of the resulting mkv version to a new mov container and
got this:
{{{
% ffprobe offset_from_mkv.mov -show_streams -show_format
ffprobe version N-56052-g59b9ecc Copyright (c) 2007-2013 the FFmpeg
developers
built on Sep 5 2013 14:16:47 with gcc 4.4.3 (Ubuntu 4.4.3-4ubuntu5.1)
configuration: --enable-nonfree --enable-gpl --enable-version3 --enable-
libvpx --enable-libtheora --enable-libvorbis --enable-libfaac --enable-
libfdk_aac --enable-libx264 --enable-libfreetype
libavutil 52. 43.100 / 52. 43.100
libavcodec 55. 31.101 / 55. 31.101
libavformat 55. 16.101 / 55. 16.101
libavdevice 55. 3.100 / 55. 3.100
libavfilter 3. 83.102 / 3. 83.102
libswscale 2. 5.100 / 2. 5.100
libswresample 0. 17.103 / 0. 17.103
libpostproc 52. 3.100 / 52. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'offset_from_mkv.mov':
Metadata:
major_brand : qt
minor_version : 512
compatible_brands: qt
encoder : Lavf55.16.101
Duration: 00:09:56.50, start: 0.000000, bitrate: 129 kb/s
Stream #0:0(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp,
128 kb/s (default)
Metadata:
handler_name : DataHandler
[STREAM]
index=0
codec_name=aac
codec_long_name=AAC (Advanced Audio Coding)
profile=unknown
codec_type=audio
codec_time_base=1/48000
codec_tag_string=mp4a
codec_tag=0x6134706d
sample_fmt=fltp
sample_rate=48000
channels=6
bits_per_sample=0
id=N/A
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/48000
start_pts=0
start_time=0.000000
duration_ts=28632040
duration=596.500833
bit_rate=128196
nb_frames=27961
nb_read_frames=N/A
nb_read_packets=N/A
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
TAG:language=eng
TAG:handler_name=DataHandler
[/STREAM]
[FORMAT]
filename=offset_from_mkv.mov
nb_streams=1
nb_programs=0
format_name=mov,mp4,m4a,3gp,3g2,mj2
format_long_name=QuickTime / MOV
start_time=0.000000
duration=596.501000
size=9671451
bit_rate=129709
probe_score=100
TAG:major_brand=qt
TAG:minor_version=512
TAG:compatible_brands=qt
TAG:encoder=Lavf55.16.101
[/FORMAT]
}}}
--
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2938#comment:2>
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