Latest post Tue, Jul 25 2017 2:31 PM by loki. 19 replies.
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  • Sun, Oct 26 2014 8:26 PM In reply to

    Re: different fps in same project/sync sound and video with different fps

    Sound files do not have a frame rate, but a sample rate that determines how fast they should be played. A file consisting of 480,000 samples would last precisely 10 seconds when played at a 48,000Hz sample rate.

    So you can manipulate the speed of sound files by playing them at a different sample rate.

    Say you have files that were recorded at 48,000Hz sample rate on set, while the camera was running 23.976fps. It means that when the picture is played back at 23.976 frames/second and sound at 48,000 samples/second, they will play in sync.

    Suppose you speed up the picture, so that you now run it at 25fps, so you play it back faster. You will need to change the speed of the sound as well. You could do that by setting the sample rate of the file to 50,050Hz [see http://24p.com/wordpress/?p=195 for an Excel sheet that lets you calculate the numbers].

    BWAV files have a sample rate stamp (a metadata entry) that tells any player at what sample rate the file was recorded and therefore at what sample rate it should be played back. Applications like Wave Agent (freeware, you need to register at SoundDevices.com) let you open one or multiple WAV files and change the sample rate stamp. This is merely a change of metadata, not an actual change to the audio data itself.

    Say you use Wave Agent to change the Sample Rate stamp from 48,000Hz to 50,050Hz, and you play back the file in, say, QT player, you will notice that it will play back the file faster [note that this also means that the pitch will sound higher, something you may want to compensate for in sound post].

    Now import that file into MC and tick the box that says "convert to project sample rate upon import" and what will happen is that the file, now stamped at a rate of 50,000Hz gets sample rate converted to 48,000Hz, but the shorter duration (faster playback) is maintained. The resulting sound clips in your bin should sync up to the sped-up picture.

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  • Thu, Feb 2 2017 11:50 PM In reply to

    • jed cahill
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    • Joined on Tue, May 10 2011
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    Re: different fps in same project/sync sound and video with different fps

    Hey wowzers that mix of frame rates looks nasty! Continuing on this old conversation I am a little confused. I have a project where I shot the bulk at 25FPS, however, there are about six clips that are in either 50FPS or 100FPS. In regards to setting them up for Online offline edit, I have created two projects one for 25fps and one for 50fps. Transcoded them to a proxy file then relinked the native file to the proxy. The problem is there is no project option to create a 100fps. 

    I would have thought that given the 25, 50, and 100 are divided into each other I could have done the transcode in simply the 25fps project. But on transcoding, I was asked if I wanted to convert the files which have a higher frame rate. when I do that they will not link the native to the proxy. So two questions... 

    1: Am I right in the workflow of creating two projects one for 25fps and one for 50fps. then opening the 50fps bin in the 25fps project to edit or is there a better way?

    2: If this is right above how do I work with higher frame rates like 100fps if I want to take them to a proxy as there is no project option for them? Or do I have to work with higher frame rates in native formats?  

     

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  • Fri, Feb 3 2017 12:30 AM In reply to

    • Mondo
    • Top 50 Contributor
    • Joined on Thu, Oct 13 2005
    • Sydney Australia
    • Posts 1,625
    • Points 18,630

    Re: different fps in same project/sync sound and video with different fps

    jed cahill:
    I have a project where I shot the bulk at 25FPS, however, there are about six clips that are in either 50FPS or 100FPS.

    Usually the only reason to shoot at those higher frame rates is for slow-motion. If that is not the intent then the only real reason for shooting at those higher rates is if you want that high motion "TV" look. Some call it through the window - good for sports, not so good for drama (IMO)

    If you just use frame skipping to get down to 25 then you'll end up with a very "juddery" looking image. (Essentially the same as using a faster shutter speed - unless its a lot of motion every frame will look like a still frame - very little motion blur) - if you blend the frames together at least you should get a more pleasing result and you won't end up with anything too odd as they are exact multiples. Essentially you'll be putting back in the motion blur you lost by using a higher frame rate (and I assume shiutter speed). I would just let Avid handle the speed conversion directly within a 25P project with motion adapters. The other solutions mentioned inthis thread are for more subtle speed changes (24-25) where you pitch and speed shift your audio to match.

    Bottom line - unless there is a very specific reason for it (eg you want use slow motion or you want to shoot high action sports) then you are much better off shooting everything at the more traditional frame rates. Certainly mix and matching is a no go unless you were going for a very specific look.

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    John

    Can we go back to the way audio nodes used to be selected? Please? ie if you have audio nodes at the same time on selected tracks; then selecting 1 audio node selects them all at that time. Having to shift select nodes or add an in and out is time consuming and counter productive. At least make it an option.

  • Fri, Feb 3 2017 12:54 AM In reply to

    • jed cahill
    • Not Ranked
    • Joined on Tue, May 10 2011
    • Australia
    • Posts 38
    • Points 500

    Re: different fps in same project/sync sound and video with different fps

    Thanks Mondo,

    Hence the bulk of the production is at 25fps. The two other frame rates are specific for speed ramping. I want to have the flexibility to ramp my motion down and back up again if I ingest it at 25fps, I would need to add frames to ramp the footage down. I have had an answer from another forum to use the new tab keep source frame rates Which I did (I think Avid has introduced to allow for this very thing) But I think it is a bit clunky as you can not link back to source from the project at 25fps you have to go to the specific frame rate project.

    Working on varying framerates is not ideal but necessary if you want motion capabilities. Any suggestions on actual workflow?

       

    Mondo:

    jed cahill:
    I have a project where I shot the bulk at 25FPS, however, there are about six clips that are in either 50FPS or 100FPS.

    Usually the only reason to shoot at those higher frame rates is for slow-motion. If that is not the intent then the only real reason for shooting at those higher rates is if you want that high motion "TV" look. Some call it through the window - good for sports, not so good for drama (IMO)

    If you just use frame skipping to get down to 25 then you'll end up with a very "juddery" looking image. (Essentially the same as using a faster shutter speed - unless its a lot of motion every frame will look like a still frame - very little motion blur) - if you blend the frames together at least you should get a more pleasing result and you won't end up with anything too odd as they are exact multiples. Essentially you'll be putting back in the motion blur you lost by using a higher frame rate (and I assume shiutter speed). I would just let Avid handle the speed conversion directly within a 25P project with motion adapters. The other solutions mentioned inthis thread are for more subtle speed changes (24-25) where you pitch and speed shift your audio to match.

    Bottom line - unless there is a very specific reason for it (eg you want use slow motion or you want to shoot high action sports) then you are much better off shooting everything at the more traditional frame rates. Certainly mix and matching is a no go unless you were going for a very specific look.

     

    HP Z600 Intel Xeon E5506 @2.13GHz 24GB RAM 64BIT [view my complete system specs]
  • Tue, Jul 25 2017 2:31 PM In reply to

    • loki
    • Not Ranked
    • Joined on Sat, Mar 17 2012
    • Posts 27
    • Points 325

    Re: different fps in same project/sync sound and video with different fps

    Hey all,

    I am in a similar project right now (25fps bulk, some c300 50fps clips for slow motion, 25fps project, keeping source framerate: so 50fps shows as 50fps and runs in slow motion) and I need to sync with external audio at 48khz.

    As this thread is quite old now, maybe someone could share their best workflow?

    Thanks in advance! 

    MC 8.8.4 OSX 10.12.4 MacPro 6,1 [view my complete system specs]
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