Audio sync

Anonymous
2012-03-14
2012-09-15
  • Anonymous

    Anonymous - 2012-03-14

    I have an mpg file created from a video_ts file (contains vob files) from a
    DVD. I used mplayer command line with defaults to extract and create it. The
    file is 42 minutes. When I play the file with mplayer the audio and video are
    synched OK. When I open the file in Lives as a clip and want to edit it, the
    audio is shown to be about ONE second shorter than the video, and the audio is
    not synched with the video. I didn't do any editing. This is just as a reult
    of opening it. This is the version 1.6.1 that is packaged with Ubuntu 11.10.
    Don't know what that translates to as far as Live's itself goes. But I suppose
    it's from the stable branch. The mpg file is standard PAL format (but I don't
    know the audio sanple rate is it 44.1k or 48k? I'm assuming 48k.) Any ideas
    anyone?

     
  • Salsaman

    Salsaman - 2012-03-14

    You can try to resync the video with audio manually. Play back the video in
    Clip Edit mode, and use the ctrl-left and ctrl-right keys to bring the audio
    back in sync with the video. Then press the "w" key - this will show you the
    sync details in the message area. After this, if the video is ahead of audio,
    you can select the first few frames and then Audio->Insert Silence in
    selection. IF audio is ahead of video : Audio -> delete selected audio.

     
  • Salsaman

    Salsaman - 2012-03-14

    Or, assuming the video and audio should end at the same point as the audio,
    just calculate the difference between audio and video tracks, select the same
    length of frames at the start of the clip, and again, insert silence in
    selection

     
  • Anonymous

    Anonymous - 2012-03-14

    Thanks. I'll try them all. Any idea why it did this?

     
  • Salsaman

    Salsaman - 2012-03-14

    Quite simply, if you start "playing" a video from the middle, audio and video
    may not always be in sync at the point you start playing (or decoding) from.

    Depends on the format, bitrates and other factors.

    IMO it is best to do nothing and then let the user take whatever action to fix
    this.

    In svn I am experimenting with a "sync_hint", but this only works for certain
    specific formats.

     
  • Don

    Don - 2012-03-15

    One question, does ctrl-left/ctrl-right move the audio or the video?

     
  • Salsaman

    Salsaman - 2012-03-15

    Ah yes, I forgot to mention that. There is a setting in Preferences/Playback :
    Audio follows video rate/direction.

    You need to make sure this is unchecked when resyncing the audio.

     
  • Don

    Don - 2012-03-16

    OK, I changed the preferences as you suggested, I synched the audio, foun out
    the difference, adjusted the audio file as required, and everything looks and
    sounds great now. Now I'm going to do things such as enhance, adjust
    contrast/brightness, edit out portions, overlay other video/sound, etc.
    finally, to convert to NTSC, is it better to do it using the Lives tools such
    as re-size and resample frame rate, or to use the encode process?

     
  • Salsaman

    Salsaman - 2012-03-16

    Use the encode process for resize and resampling. It will suggest the best
    values for you.

     
  • Don

    Don - 2012-03-17

    I tried "back up to *.lv1" and it is taking a really long time. Is this
    normal.

     
  • Salsaman

    Salsaman - 2012-03-18

    Yes it can be. The current subversion has a much faster backup/restore, which
    will be released in the next version, 1.6.2.

     
  • Don

    Don - 2012-03-20

    Thanks. So, I've applied effects, enhanced, etc.. Aspect ratio is retained, so
    no distortions were introduced during the conversion to NTSC. Audio is
    synched. I added other audio as well. I must say the encoded file is of
    EXTREMELY high quality. If time is not a concern, this is the absolute best
    editing tool I've seen.

     
  • Salsaman

    Salsaman - 2012-03-20

    Glad you appreciate it !

     

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