[FFmpeg-user] ct a video precisly

[Henk D. Schoneveld]

On 16 Sep 2015, at 11:33, gagall at free.fr wrote:

> Hello,
> 
> I'm trying to cut a video to get 12s sequences. It needs to be accurate.
Cutting is done on begin and end of a Group Of Pictures, a GOP.
Splitting always occurs the way you mention, it is ‘about 12 seconds’
What is, could be the reason, you need it absoute accurate ?
One way around could be to 1st encode your source to all I-frame, key frames. This way you get a GOP-size of 1 and then you can get it accurate.
> But when I ask a 12 seconds sequence (not from the begining for this example) , I get around 12:01 seconds.
> The command line is :
> ffmpeg -ss 00:00:00.00 -i GOPR0151.mp4 -b:v 30150 -t 00:00:12.00 -acodec copy -vcodec copy GOPR0151_002.mp4
> 
> and even, when I start from 00:02:12.00, the output lasts 12:33 seconds.
> 
> Can anybody tell me who to get more accuracy, please ?
> I noticed that the bitrate is not the same in the orginal video than in the output. Is it important ?
> Here are the informations of the original video :
> ffprobe.exe GOPR0151.mp4
> ffprobe version N-74751-gb54e03c Copyright (c) 2007-2015 the FFmpeg developers
>  built with gcc 4.9.3 (GCC)
>  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnu
> tls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libdcadec --enable-libfreetype --enable-libgme --enab
> le-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable
> -libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --ena
> ble-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --e
> nable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enable-zlib
>  libavutil      54. 31.100 / 54. 31.100
>  libavcodec     56. 59.100 / 56. 59.100
>  libavformat    56. 40.101 / 56. 40.101
>  libavdevice    56.  4.100 / 56.  4.100
>  libavfilter     5. 40.100 /  5. 40.100
>  libswscale      3.  1.101 /  3.  1.101
>  libswresample   1.  2.101 /  1.  2.101
>  libpostproc    53.  3.100 / 53.  3.100
> Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'GOPR0151.mp4':
>  Metadata:
>    major_brand     : avc1
>    minor_version   : 0
>    compatible_brands: avc1isom
>    creation_time   : 2014-10-25 09:19:36
>  Duration: 00:17:24.30, start: 0.000000, bitrate: 30150 kb/s
>    Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt709), 1280x960 [SAR 1:1 DAR 4:3], 30002 kb/s, 100 fps, 100 tbr, 180k tbn,
> 200 tbc (default)
>    Metadata:
>      creation_time   : 2014-10-25 09:19:36
>      handler_name    :  GoPro AVC
>      encoder         : GoPro AVC encoder
>    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
>    Metadata:
>      creation_time   : 2014-10-25 09:19:36
>      handler_name    :  GoPro AAC
> 
> 
> And the output :
> ffprobe.exe GOPR0151_002.mp4
> ffprobe version N-74751-gb54e03c Copyright (c) 2007-2015 the FFmpeg developers
>  built with gcc 4.9.3 (GCC)
>  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnu
> tls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libdcadec --enable-libfreetype --enable-libgme --enab
> le-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable
> -libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --ena
> ble-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --e
> nable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enable-zlib
>  libavutil      54. 31.100 / 54. 31.100
>  libavcodec     56. 59.100 / 56. 59.100
>  libavformat    56. 40.101 / 56. 40.101
>  libavdevice    56.  4.100 / 56.  4.100
>  libavfilter     5. 40.100 /  5. 40.100
>  libswscale      3.  1.101 /  3.  1.101
>  libswresample   1.  2.101 /  1.  2.101
>  libpostproc    53.  3.100 / 53.  3.100
> Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'GOPR0151_002.mp4':
>  Metadata:
>    major_brand     : isom
>    minor_version   : 512
>    compatible_brands: isomiso2avc1mp41
>    encoder         : Lavf56.40.101
>  Duration: 00:00:12.33, start: 0.309333, bitrate: 30273 kb/s
>    Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt709), 1280x960 [SAR 1:1 DAR 4:3], 30187 kb/s, 100 fps, 100 tbr, 180k tbn,
> 200 tbc (default)
>    Metadata:
>      handler_name    : VideoHandler
>    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
>    Metadata:
>      handler_name    : SoundHandler
> 
> 
> Thanks in advance
> 
> Fridu
> _______________________________________________
> ffmpeg-user mailing list
> ffmpeg-user at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-user