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Forums Avid Media Composer sync and frame rate confusion

  • sync and frame rate confusion

  • Philip James

    May 15, 2018 at 9:28 am

    I have some mp4 footage that plays in sync in Quicktime and when I ‘get info’ in that programme it says it is at 25 fps. When I link or import it into my 25 fps project in MC the sound is out of sync. When I check the clips in MediaInfo app I get:

    Frame rate mode : Variable
    Frame rate : 25.000 fps
    Minimum frame rate : 24.390 fps
    Maximum frame rate : 25.641 fps
    Original frame rate : 29.970 (30000/1001) fps
    Standard : NTSC

    So it is identifying this as 25 fps footage but with an orginal frame rate of 29.97. And the listed standard is NTSC. So I created a new MC project at 29.97 and then AMA linked to the footage and it’s out of sync. In the FPS column in the Bin it says that the frame rate of these linked clips is 25.03 fps. I think this frame rate might be key because I worked out that the audio sync error was around 19 frames in my 25 fps project and that matches the error caused by a clip at 25.03 fps in a 25 fps project.

    What should I do?


  • Philip James

    May 15, 2018 at 2:51 pm

    Thank you.

    I agree with you. However this was not shot on a phone. This was a multi-camera shoot by a professional production company at a music festival. Maybe their conversion of the performance screwed things up. I’m not sure. I’m trying to get a higher res conversion. I will try and find out more about how I ended up with 25.03 fps clips. Quicktime can play them fine though – in sync – is that because it can work at variable frame rates?


  • Shane Ross

    May 15, 2018 at 3:53 pm

    Wait…if you need something to use for EDITING…don’t have them send you a compressed file like that. They need to send you a master quality QT file…in ProRes or DNxHD or other editing codec. Mp4…no, that’s a delivery codec.

    Little Frog Post
    Read my blog, Little Frog in High Def

  • Philip James

    May 15, 2018 at 4:05 pm

    I suspect that ‘variable frame rate ‘ was selected when they did the .mp4 conversion.

  • Philip James

    May 15, 2018 at 4:07 pm

    I’m working on that and they say they can supply it but I wanted to do an offline with the mp4 for now. They are not my client as such – it was my performance and they were shooting it for the festival. I imagine the screw up was caused when someone converted to .mp4.

  • Shane Ross

    May 15, 2018 at 5:14 pm

    Warning…if you offline with the MP4 files, you will not be able to relink to the master file at all…you’ll need to manually over cut. There’s no metadata to make it link properly.

    Little Frog Post
    Read my blog, Little Frog in High Def

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