audio out of sync after download

Discussion in 'Digital Video' started by Mudo2, May 7, 2010.

  1. Mudo2 macrumors newbie

    May 7, 2010

    In work each month I film some footage on a Canon HD legria camera and edit it in final cut express. When I export the final film file it always plays perfectly on my computer but i then upload to a server and back down onto some screens located around the offices and the audio moves out of sync with the video, usually by about a second.

    The camera frame size is 1440x1080, Vid rate is 25fps, the audio rate is 48.0KHz and the audio format is 16 bit integer.

    I exported using H.264 compression, I changed the dimesions to 1280 x 720 and I de-interlaced the source video, i left the sound settings in fce on default which is 48KHz and I greatly compressed the actual quality of the clip, as it needs to be uploaded to a server.

    Hopefully somebody can see the error in my approach.
  2. huntercr macrumors 65816

    Jun 6, 2006

    What bitrate did you used for the H.264 video?

    Also...This may not solve your problem at all, but did you actually shoot 25fps interlaced? My quick look at the specs of the legria suggests to me that its 25fps recording mode is already progressive.
  3. Mudo2 thread starter macrumors newbie

    May 7, 2010
    Hi and thanks for replying,

    According to the file info, the bit rate is 2.89Mbps. although i don't recall actually entering info to set the bit rate, i think it did this automatically.

    Additional info; the video track is 1.35Mbps and the audio track is 1.54 Mbps.

    Is it possible to sync audio and video within a .mov file without having having to go back to the FCE project file and changing the settings and re-saving the entire project, as the finished file is nearly 17mins in lenght?
  4. Mudo2 thread starter macrumors newbie

    May 7, 2010
    sorry in relation to the other question, the frame rate is 50i as standard (not sure what that means) but all the individual shots that I imported into FCE state that they are 25fps, when I check the item properties.

    I deinterlaced the footage before I exported as FCE doesn't seem to deal with AVCHD files particularly well if the they are not deinterlaced.
  5. huntercr macrumors 65816

    Jun 6, 2006
    Unlikely... but I'm still thinking this is some other odd thing.
    Are you sure that the resulting MOV file plays fine on your system after you encode? It only goes out of sync on other people's systems?
  6. Mudo2 thread starter macrumors newbie

    May 7, 2010
    I always play the finished file once to make sure that it is OK, on both a mac and a PC and it plays fine...........but the initial time it plays on the computers that I download it to around the office, it will play fine also, but I play it on a loop and over time the audio moves more and more out of sync.

    I think that I am supposed use the apple intermediate codec to compress avched files with fce 4.0.1 but the H.264 codec allows me to compress the file to a much greater extent. I have also tried converting to mp4 after it has been exported and it still happens.

    I don't understand how it can occassionally play in sync and then move out of sync..........

    Can de-interlacing have an effect on the audio or the frame rate?
  7. spinnerlys Guest


    Sep 7, 2008
    forlod bygningen
    What kind of software and system do you use to play the video back in your office, as the problem seems to be stemming from there and not the encoding.

    AIC (Apple Intermediate Codec) is meant for editing, H264 is meant for distribution and saving storage space, so H264 was the right choice.
  8. Mudo2 thread starter macrumors newbie

    May 7, 2010
    I just checked the files on my colleagues computer using a windows media player and they moved out of sync, they play using an adobe flash player on the devices in the office and they also move out of sync...........sometimes.

    I just realised that the easy set up on FCE was not set to AIC when I was originally ingesting the files from the memory card? could this be the problem? although the audio plays fine within FCE when the files are in the timeline.
  9. huntercr macrumors 65816

    Jun 6, 2006
    In general, de-interlacing shouldn't affect it.

    You're supposed to use AIC codec for importing to FCE ( check your sequence settings "Easy setup" ) Exporting to H.264 is fine... that's the codec you're supposed to use if you're sharing it to the web or any "final destination" point where you're not going to edit it anymore.

    deinterlacing should not normally affect the audio, but yo might want to look into the 25p mode on your camera to make sure there isn't some sort of special frame pulldown you're supposed to run. Final Cut won't do that for you IIRC.
  10. Mudo2 thread starter macrumors newbie

    May 7, 2010
    Thanks for the help.

    One final question in a bid to save the work that is already completed.
    Do you think it would be possible to rectify the video and audio sync problems by separating them and trying to save them again using different settings in a program like streamclip or even back into FCE?
  11. huntercr macrumors 65816

    Jun 6, 2006
    Well, it's possible but you will lose quality when you re-export the finished product.

    We still don't know for certain what your sync problem is. If I had to guess, I would actually think you've discovered a bug in quicktime or something since as you said, the more times you play it the more out of sync it becomes.
  12. Mudo2 thread starter macrumors newbie

    May 7, 2010
    I thought it might be related the fact that I didn't use the correct easy set-up settings in FCE.
    Another possibility, that I just thought of, is that I sometimes I import other footage into the FCE timeline that wasn't shot on my camera.......I wonder if this wasn't converted to the same settings as my own footage could it be the culprit.
    Do you have any ideas as to how I might save the completed film file. I still have the project file with all the clips and sequences. Do you think if I set up a new project in FCE with the easy setup settings set to AIC 1080i x 50i and copy and pasted the entire project into it and exported again it might work? or is there another application that I could use to try to save it again?

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