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Thread: How to convert flv file to Theora : best practices

  1. #1
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    How to convert flv file to Theora : best practices

    Hi,

    I already posted this message on the General Help forum, but I'm afraid it's more for this one.

    I have a video file in the .flv format, which I would like to convert in the Theora (.ogv) format (I prefer free open source format ).

    For that I type this command in the terminal :

    Code:
    ffmpeg -i myfile.flv myfile.ogv
    The video and audio streams are correctly identified, but the conversion takes a very long time and the resulting file in Theora is very heavy. Moreover, when I play it, the audio quality is okay (I don't notice any difference with the original) but the video quality is terrible .

    I would like to know if I may get better results by using additonal options to the in the ffmpeg command and what are the recommended best pratices in this kind of work.

    Many thanks

  2. #2
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    Re: How to convert flv file to Theora : best practices

    Quote Originally Posted by le_phoceen View Post
    I would like to know if I may get better results by using additonal options to the in the ffmpeg command and what are the recommended best pratices in this kind of work.
    The default encoding settings for FFmpeg are not always very good, but they can be improved with a few options. Example:
    Code:
    ffmpeg -i input -vcodec libtheora -qscale 6 -acodec libvorbis -aq 5 output.ogv
    The important options here are qscale and aq:
    • qscale - adjust video quality. I believe the qscale range for libtheora is 0 to 10. A higher value is a higher quality. Use the lowest value that still has an acceptable quality.
    • aq - adjust audio quality. Should be similar to the q option in oggenc. A higher value is higher quality. See the Recommended Vorbis Encoder Settings for more info on what values to use. Range is -2 to 10, but I'm not sure if FFmpeg can use the negative values.
    Last edited by FakeOutdoorsman; December 12th, 2011 at 12:22 AM. Reason: typo: change libvorbis to libtheora.

  3. #3
    Join Date
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    Re: How to convert flv file to Theora : best practices

    Thank you very much FakeOutdoorsman . I get much better results now.
    Last edited by le_phoceen; December 12th, 2011 at 09:50 AM.

  4. #4
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    Re: How to convert flv file to Theora : best practices

    Quote Originally Posted by FakeOutdoorsman View Post
    • qscale - adjust video quality. I believe the qscale range for libtheora is 0 to 10.
    Certainly a grep through the FFmpeg source seems to confirm this. This comment in libavcodec/libtheoraenc.c:

    Code:
    /* to be constant with the libvorbis implementation, clip global_quality to 0 - 10
    You think that's air you're breathing now?

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