[Libav-user] [resize video] Lost duration

[Hung Nguyen]

Hi Carl,

Now I can get the video duration if I force enc_ctx (AVFormatContext) ’s time_base into (AVRational){1, 24} or something like this.
The problem is the duration of input video is different from output video, even when I try with ffmpeg (the application)

The input:
ffmpeg -i original
ffmpeg version 2.4.1 Copyright (c) 2000-2014 the FFmpeg developers
  built on Oct  7 2014 09:23:21 with gcc 4.6 (Ubuntu/Linaro 4.6.4-3ubuntu1)
  configuration: --enable-libx264 --enable-libfdk-aac --enable-gpl --enable-nonfree --enable-shared --enable-avresample --enable-debug=3 --enable-libfaac --enable-libvo-aacenc --enable-version3
  libavutil      54.  7.100 / 54.  7.100
  libavcodec     56.  1.100 / 56.  1.100
  libavformat    56.  4.101 / 56.  4.101
  libavdevice    56.  0.100 / 56.  0.100
  libavfilter     5.  1.100 /  5.  1.100
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  0.100 /  3.  0.100
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  0.100 / 53.  0.100
Input #0, mpegts, from 'original.ts':
  Duration: 00:00:10.14, start: 20.818667, bitrate: 1720 kb/s
  Program 1
    Stream #0:0[0x64]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p, 854x480 [SAR 1:1 DAR 427:240], 25 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0:1[0x65]: Audio: aac ([15][0][0][0] / 0x000F), 48000 Hz, stereo, fltp, 130 kb/s


The output:
ffmpeg -i output
ffmpeg version 2.4.1 Copyright (c) 2000-2014 the FFmpeg developers
  built on Oct  7 2014 09:23:21 with gcc 4.6 (Ubuntu/Linaro 4.6.4-3ubuntu1)
  configuration: --enable-libx264 --enable-libfdk-aac --enable-gpl --enable-nonfree --enable-shared --enable-avresample --enable-debug=3 --enable-libfaac --enable-libvo-aacenc --enable-version3
  libavutil      54.  7.100 / 54.  7.100
  libavcodec     56.  1.100 / 56.  1.100
  libavformat    56.  4.101 / 56.  4.101
  libavdevice    56.  0.100 / 56.  0.100
  libavfilter     5.  1.100 /  5.  1.100
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  0.100 /  3.  0.100
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  0.100 / 53.  0.100
Input #0, mpegts, from 'ffmpeg.ts':
  Duration: 00:00:10.17, start: 1.429978, bitrate: 907 kb/s
  Program 1
    Metadata:
      service_name    : Service01
      service_provider: FFmpeg
    Stream #0:0[0x100]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv), 640x360 [SAR 1:1 DAR 16:9], max. 104857 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0:1[0x101]: Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, s16p, 372 kb/s

Duration of input is  00:00:10.14 but the output is 00:00:10.17

Command I use:
/usr/local/bin/ffmpeg -v debug -y -i original -vcodec libx264 -vb 500000 -s 640x360 -f mpegts -aspect 16:9 -vf scale=640:-1 output


How can I keep the original duration after transcoding the video?

Thanks,

Hung



On Oct 14, 2014, at 8:59 AM, Hung Nguyen <Hung.Nguyen at ambientdigitalgroup.com<mailto:Hung.Nguyen at ambientdigitalgroup.com>> wrote:

Hi Carl,

Yes, I also scale the input using scale filter.
The filter I use is as following:
filter_spec = "scale=iw*min(640/iw\\,360/ih):ih*min(640/iw\\,360/ih), pad=640:360:(640-iw*min(640/iw\\,360/ih))/2:(360-ih*min(640/iw\\,360/ih))/2”;

I still don’t understand why scale video cause duration metadata lost.

Thanks,

—
Hưng



On Oct 13, 2014, at 11:59 PM, Carl Eugen Hoyos <cehoyos at ag.or.at<mailto:cehoyos at ag.or.at>> wrote:

Hung Nguyen <Hung.Nguyen at ...> writes:

The problem I am facing now is, every time I try to
change video size when initialise encoder, the
output video does not have video duration:

enc_ctx->height = 360;
enc_ctx->width = 640;

Did you just set the dimensions in the codec context
or did you also use the scale your input (with the
scale filter)?

Carl Eugen

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