[FFmpeg-user] Why does fps == 1 for a webm videos?

Misha Penkov misha.penkov at gmail.com
Thu Mar 21 12:06:30 CET 2013


On 21 March 2013 19:38, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:

> > I have a webm video that is played back correctly with
> > ffplay. However, its fps is incorrect:
>
> (Why do you think so?)


It match the rate at which ffplay is playing it (which seems to be around
25-30fps).  Isn't that a problem?


> > While it doesn't affect playback, it creates problems
> > when I convert the video using ffmpeg.
>
> Please provide your failing command line together with
> complete, uncut console output.
>

Here it is:

misha at misha-lmd:~/git/video-signature/gitignore/cz_clusters/0003$ ffmpeg -y
-i 8szDFB30azA.webm -vcodec rawvideo -acodec none -s qcif test.yuv
ffmpeg version N-51169-gcedf276 Copyright (c) 2000-2013 the FFmpeg
developers
  built on Mar 21 2013 18:12:33 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
  configuration: --enable-gpl --enable-libass --enable-libfaac
--enable-libfdk-aac --enable-libmp3lame --enable-libopencore-amrnb
--enable-libopencore-amrwb --enable-libspeex --enable-librtmp
--enable-libtheora --enable-libvorbis --enable-libvpx --enable-x11grab
--enable-libx264 --enable-nonfree --enable-version3 --enable-shared
--enable-pic
  libavutil      52. 22.100 / 52. 22.100
  libavcodec     55.  1.100 / 55.  1.100
  libavformat    55.  0.100 / 55.  0.100
  libavdevice    55.  0.100 / 55.  0.100
  libavfilter     3. 48.100 /  3. 48.100
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
Input #0, matroska,webm, from '8szDFB30azA.webm':
  Duration: 00:15:18.62, start: 0.000000, bitrate: 546 kb/s
    Stream #0:0(eng): Video: vp8, yuv420p, 640x360, SAR 1:1 DAR 16:9, 1k
fps, 1k tbr, 1k tbn, 1k tbc (default)
    Stream #0:1: Audio: vorbis, 44100 Hz, mono, fltp (default)
Output #0, rawvideo, to 'test.yuv':
  Metadata:
    encoder         : Lavf55.0.100
    Stream #0:0(eng): Video: rawvideo (I420 / 0x30323449), yuv420p, 176x144
[SAR 16:11 DAR 16:9], q=2-31, 200 kb/s, 90k tbn, 1k tbc (default)
Stream mapping:
  Stream #0:0 -> #0:0 (vp8 -> rawvideo)
Press [q] to stop, [?] for help
frame=918501 fps=1640 q=0.0 Lsize=34099350kB time=00:15:18.50
bitrate=304128.0kbits/s dup=890945 drop=0
video:34099350kB audio:0kB subtitle:0 global headers:0kB muxing overhead
0.000000%

The problem is that test.yuv now contains many more frames that there
really were in the webm file, with a majority of those frames being
duplicates.  This is not what I want -- I want to extract all the frames
from the webm file as they are, without any duplicates.

If I play the resulting file (ffplay test.yuv -s qcif), it plays back
approximately 30 times slower than the original file:

If you're interested in the original webm file, it's available from youtube
(youtube-dl 8szDFB30azA -f 43)

Cheers,
Michael


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