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Thread: OGV-AVI Problems - mencoder/ffmpeg/xvid/x264

  1. #1
    Join Date
    May 2008
    Beans
    1,029

    Question OGV-AVI Problems - mencoder/ffmpeg/xvid/x264

    I am having all kinds of trouble converting a video that I created with recordmydesktop. I first tried encoding the OGV to AVI with mencoder:

    Code:
    mencoder apt_segfault.ogv -ovc xvid -xvidencopts pass=1:bitrate=1400 -oac mp3lame -lameopts cbr:br=128 -o apt_segfault.avi
    But only a small portion of the video is encoded and is off sync with the audio. I tried with the x264 codec as well and got the same result.

    I then decided to try ffmpeg:

    Code:
    ffmpeg -i apt_segfault.ogv -vcodec libxvid -b 1400k -acodec libmp3lame -ab 128k apt_segfault.avi
    The whole video encodes and works fine. My only complaint is that I can't improve the video quality. Setting the video bitrate (-b 1400k) didn't seem to make a difference. The video has turned out at 201Kbps. The same thing happens with mencoder, passing 'bitrate=1400' to xvidencopts doesn't affect anything.

    Also, when trying to use x264 with ffmpeg I get the following errors:

    Code:
    ffmpeg -i apt_segfault.ogv -vcodec libx264 -acodec libmp3lame -ab 128k apt_segfault.avi
    
    ...
    ...
    ...
    [ogg @ 0x8e88bc0]max_analyze_duration reached
    Input #0, ogg, from 'apt_segfault.ogv':
      Duration: 00:04:22.93, start: 0.000000, bitrate: 382 kb/s
        Stream #0.0: Data: skeleton
        Stream #0.1: Video: theora, yuv420p, 1024x768 [PAR 1:1 DAR 4:3], 15 fps, 15 tbr, 15 tbn, 15 tbc
        Stream #0.2: Audio: vorbis, 44100 Hz, mono, s16, 239 kb/s
    File 'apt_segfault.avi' already exists. Overwrite ? [y/N] y
    [libx264 @ 0x8e8c290]broken ffmpeg default settings detected
    [libx264 @ 0x8e8c290]use an encoding preset (vpre)
    Output #0, avi, to 'apt_segfault.avi':
        Stream #0.0: Video: libx264, yuv420p, 1024x768 [PAR 1:1 DAR 4:3], q=2-31, 200 kb/s, 90k tbn, 15 tbc
        Stream #0.1: Audio: libmp3lame, 44100 Hz, mono, s16, 128 kb/s
    Stream mapping:
      Stream #0.1 -> #0.0
      Stream #0.2 -> #0.1
    Error while opening encoder for output stream #0.0 - maybe incorrect parameters such as bit_rate, rate, width or height
    So if anybody has any ideas why mencoder fails to encode the entire video or can tell me how to increase the video bitrate in ffmpeg, please let me know.

  2. #2
    Join Date
    May 2008
    Beans
    1,029

    Re: OGV-AVI Problems - mencoder/ffmpeg/xvid/x264

    I figured out what was wrong with libx264 and ffmpeg. Apparently the default settings for libx264 are broken and a video preset needs to be declared with the '-vpre' flag:

    Code:
    ffmpeg -i apt_segfault.ogv -vcodec libx264 -vpre lossless_ultrafast ...

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