[FFmpeg-user] ffmpeg record from usb webcam give huge sync problem

Sun Feb 22 23:14:27 CET 2015

Sorry for late post. I have an ideea and tested to see wich is exact
relation between video and audio.
So I filmed myself count of 10 speaking and pointing with fingers.
Video is show from begining but is cut in final (about 5s) and sound
is cut from begining (about 5s) so start from six until ten.
It's some kind of mix: video first 5s and sound last 5s.

On Mon, Feb 23, 2015 at 12:03 AM, Vlăduţ Frăţiman
<fratiman.vladut at gmail.com> wrote:
> Yes u are right, -s shoul be "-video_size" and -r => -framerate.
> But not here are main problem. I make more test, i read everything i
> found but still no solution (after two days).
> For moment my command is to encode as avi (xvid) because seem to be
> faster than mp4 encoding.
> So command is: ./ffmpeg -y -f v4l2 -video_size 640x360 -framerate 5 -i
> /dev/video0 -f alsa -ac 1 -i hw:1,0 -vcodec mpeg4 -vtag xvid -acodec
> libmp3lame -q 3 -ab 96k output2.avi
>
> Output is this:
> ./ffmpeg -y -f v4l2 -video_size 640x360 -framerate 5 -i /dev/video0 -f
> alsa -ac 1 -i hw:1,0 -vcodec mpeg4 -vtag xvid -acodec libmp3lame -q 3
> -ab 96k output2.avi
> ffmpeg version N-43517-gac424b2-   http://johnvansickle.com/ffmpeg/
> Copyright (c) 2000-2015 the FFmpeg developers
>   built with gcc 4.9.2 (Debian 4.9.2-10)
>   configuration: --enable-gpl --enable-version3 --disable-shared
> --disable-debug --enable-runtime-cpudetect --enable-libmp3lame
> --enable-libx264 --enable-libx265 --enable-libwebp --enable-libspeex
> --enable-libvorbis --enable-libvpx --enable-libfreetype
> --enable-fontconfig --enable-libxvid --enable-libopencore-amrnb
> --enable-libopencore-amrwb --enable-libtheora --enable-libvo-aacenc
> --enable-libvo-amrwbenc --enable-gray --enable-libopenjpeg
> --enable-libopus --enable-libass --enable-gnutls --enable-libvidstab
> --cc=gcc-4.9
>   libavutil      54. 19.100 / 54. 19.100
>   libavcodec     56. 25.101 / 56. 25.101
>   libavformat    56. 23.103 / 56. 23.103
>   libavdevice    56.  4.100 / 56.  4.100
>   libavfilter     5. 11.100 /  5. 11.100
>   libswscale      3.  1.101 /  3.  1.101
>   libswresample   1.  1.100 /  1.  1.100
>   libpostproc    53.  3.100 / 53.  3.100
> [video4linux2,v4l2 @ 0xb941a20] The driver changed the time per frame
> from 1/5 to 2/15
> Input #0, video4linux2,v4l2, from '/dev/video0':
>   Duration: N/A, start: 367.470086, bitrate: 27648 kb/s
>     Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422,
> 640x360, 27648 kb/s, 7.50 fps, 7.50 tbr, 1000k tbn, 1000k tbc
> Guessed Channel Layout for  Input Stream #1.0 : mono
> Input #1, alsa, from 'hw:1,0':
>   Duration: N/A, start: 1424641531.273806, bitrate: 768 kb/s
>     Stream #1:0: Audio: pcm_s16le, 48000 Hz, 1 channels, s16, 768 kb/s
> Output #0, avi, to 'output2.avi':
>   Metadata:
>     ISFT            : Lavf56.23.103
>     Stream #0:0: Video: mpeg4 (xvid / 0x64697678), yuv420p, 640x360,
> q=2-31, 200 kb/s, 7.50 fps, 7.50 tbn, 7.50 tbc
>     Metadata:
>       encoder         : Lavc56.25.101 mpeg4
>     Stream #0:1: Audio: mp3 (libmp3lame) (U[0][0][0] / 0x0055), 48000
> Hz, mono, s16p, 96 kb/s
>     Metadata:
>       encoder         : Lavc56.25.101 libmp3lame
> Stream mapping:
>   Stream #0:0 -> #0:0 (rawvideo (native) -> mpeg4 (native))
>   Stream #1:0 -> #0:1 (pcm_s16le (native) -> mp3 (libmp3lame))
> Press [q] to stop, [?] for help
> frame=    4 fps=0.0 q=3.0 size=      48kB time=00:00:00.53 bitrate=
> 743.1kbits/sframe=    8 fps=7.9 q=3.0 size=      75kB time=00:00:01.06
> bitrate= 578.8kbits/sframe=   10 fps=6.6 q=3.0 size=      92kB
> time=00:00:01.73 bitrate= 432.7kbits/sframe=   13 fps=6.4 q=3.0 size=
>    113kB time=00:00:02.26 bitrate= 409.4kbits/sframe=   15 fps=5.9
> q=3.0 size=     138kB time=00:00:02.80 bitrate= 403.4kbits/sframe=
> 17 fps=5.6 q=3.0 size=     161kB time=00:00:03.20 bitrate=
> 412.3kbits/sframe=   20 fps=5.7 q=3.0 size=     195kB time=00:00:03.60
> bitrate= 443.9kbits/sPast duration 0.908470 too large
> Past duration 0.732430 too large
> Past duration 0.735619 too large
> Past duration 0.799629 too large
> frame=   24 fps=5.9 q=3.0 size=     231kB time=00:00:04.13 bitrate= 457.4kbits/s
>
> I see some message that is repeated: Past duration xxxxxxxxx too large
>
> Problem i think is with uvcview driver wich is used by my cam.
> According with this post:
> https://lkml.org/lkml/2014/3/28/12
> here are some problems with timestamp in v4l2 buffers
> Follow this bugtrac: https://trac.ffmpeg.org/ticket/692#comment:15
> tested ffmpeg with all option: -ts abs or mono2abs. Loaded uvcview
> kernel module with "modprobe uvcvideo clock=realtime" but no change.
> I'm not shure if current uvcview have patch mentioned in first link.
> Everytime i get video about 7s later from sound.
>
> On Sun, Feb 22, 2015 at 9:13 PM, Moritz Barsnick <barsnick at gmx.net> wrote:
>> On Sun, Feb 22, 2015 at 09:42:40 +0200, Vlăduţ Frăţiman wrote:
>>> ffmpeg -y -f v4l2 -s 640x360 -framerate 5 -i /dev/video0 -f alsa -ac 1 -i default:CARD=HD3000 -pix_fmt yuv420p -c:v libx264 -q:v 20 -r 5 -preset ultrafast -strict -2 -c:a aac capture.mkv
>>
>> I believe "-s" should be "-video_size".
>> I believe "-q:v" has no effect on libx264, but I may be wrong.
>>
>> That said:
>>
>>> The main problem is that audio and video are totally out of sync.
>>> Probably each device (video and audio) will not start simultaneously.
>>> Is there any parameter to ensure that the two devices are ready
>>> simultaneously so when recording, video and audio will be in sync?
>>> In my case, audio start much faster. At begining video is freezing and
>>> hear audio, then both play obviously out of sync and then audio is
>>> finishing and video still playing until finish.
>>
>> Please show us the complete console output from the ffmpeg command.
>>
>> Moritz
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