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Thread: reencoding video with low fps (ffmpeg or mencoder)

  1. #1
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    reencoding video with low fps (ffmpeg or mencoder)

    I have a couple of video captures done with recordmydesktop. These desktop captures sometimes also include the playing of videos, such that you can see the time go by in the player.

    The problem which I only realized quite latter is that they were capped at 15 fps (or some other low value), using theora format, and because of that when I play then with mplayer the video looks like its being fast forwarded.

    I would like to know how can I fix this problem.
    My idea would be to have the reencoding tool (ffmpeg or mencoder) duplicate each frame and thus make it look like time flows normally (even though the end result could look like a very fast slideshow). How can I do this?

    Any other suggestions?

    Thanks

  2. #2
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    Re: reencoding video with low fps (ffmpeg or mencoder)

    Quote Originally Posted by kung fu buntu View Post
    I would like to know how can I fix this problem.
    Play it back with a different program? Don't you wish software would actually work? Try the VLC player. That's rather independent of most other media software. If that plays back at the correct speed, than you can suspect that the other playback program is at fault. Otherwise, the recording program stored the frame rate incorrectly.

    Let's see, how to fix the file? Check the ffmpeg manual??

  3. #3
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    Re: reencoding video with low fps (ffmpeg or mencoder)

    you can set the fps in tragtor
    its a fast program

  4. #4
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    Re: reencoding video with low fps (ffmpeg or mencoder)

    Quote Originally Posted by VanillaMozilla View Post
    Play it back with a different program? Don't you wish software would actually work? Try the VLC player. That's rather independent of most other media software. If that plays back at the correct speed, than you can suspect that the other playback program is at fault. Otherwise, the recording program stored the frame rate incorrectly.

    Let's see, how to fix the file? Check the ffmpeg manual??
    VLC is not any better than mplayer. The same thing happens.
    I also tried playing the video with theora_player_example and the playback is still borked.



    Quote Originally Posted by no2498 View Post
    you can set the fps in tragtor
    its a fast program
    That won't solve the problem. I already tried passing the fps option (-r) with ffmpeg using different values.






    I did some more testing and investigation into this issue...

    When I mentioned the 15-18 fps I was wrong. It was recorded at 30 fps, however how it was really captured that is another issue because the playback shows that frames are missing (thus the playback looking like it's in fast forward mode).


    Code:
    $ mediainfo foo.ogg 
    General
    ID                               : 1333266807 (0x4F780977)
    Complete name                    : foo.ogg
    Format                           : OGG
    File size                        : 70.2 MiB
    Duration                         : 2mn 28s
    Overall bit rate                 : 3 966 Kbps
    recordMyDesktop                  : 0.3.7.3
    
    Video
    ID                               : 1770862840 (0x698D38F8)
    Format                           : Theora
    Duration                         : 2mn 28s
    Bit rate                         : 3 628 Kbps
    Nominal bit rate                 : 45.0 Kbps
    Width                            : 1 280 pixels
    Height                           : 1 024 pixels
    Display aspect ratio             : 5:4
    Frame rate                       : 30.000 fps
    Bits/(Pixel*Frame)               : 0.092
    Writing library                  : libTheora 3.2.1 (UTC 2008-10-20)
    Code:
    $ theora_dump_video < foo.ogg  > foo.dump
    Encoded by Xiph.Org libTheora I 20081020 3 2 1
    theora comment header:
            recordMyDesktop=0.3.7.3
    Ogg logical stream 698d38f8 is Theora 1280x1024 30.00 fps video
    Encoded frame content is 1280x1024 with 0x0 offset
    4459 frames
    Done.
    148 seconds * 30 frames = 4440 frames
    So it confirms the 30 fps


    Based on the playback of the capture (which includes a video being played with time) I could conclude that:
    133 seconds of real world time were condensed into 101 seconds of desktop capture

    So it's possible that these captures are foobared beyond repair.
    Even if I could find a way to duplicate each frame that would produce the opposite effect. It would mean 133 seconds of real world being "slowed down" into 202 seconds of playback.
    I would need to use decimal slowdown factor, which may not be even possible to get.


    Any other ideas?
    Last edited by kung fu buntu; May 11th, 2011 at 11:56 PM.

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