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  • Thu, Sep 14 2017 7:49 AM

    • zonik
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    discussion clean framerate conversion

    I'd like to start a discussion about the framerate conversion within media composer. Especially when changing the source playback rate. What alters the speed, but does no frame-blending. Technically it's no conversion on the video side. Every frame in the source is one in the timeline. But on the audio side you have to change the speed.

    24.976 -> 25 fps = 95,904 % of original duration.

    The ability to mix framerates in the timeline is a good starting point. When editing a documentary in the PAL area (25p) I get a lot of clips by worldwide archives with different framerates. I link the footage or import it to DNxHR, keep the source framerate and edit it to my timeline, where the timewarp does his job to match the timeline framerate. It's a quick and dirty style. Of course you get interframe-blending (or stutter).

    When the source framerate and the timeline framerate are close, like 23.976 -> 25 it's a good way to alter the playback framerate in the clip's source settings. The clip duration alters as well, but you get a clean frame by frame result without frame-blending.

    And yes, audio is treated as well. But simply by playback speed. (=pitch shift) Not by resampling.

    Now the problems begin. When exporting an AAF to the record studio for mixing, media composer tumbles over it's own conversion. After AAF export the exported timeline has different durations than the original timeline. And some frame gaps. Same result when simply consolidate the timeline to another drive.

    Next point, when editing a source altered clip (e.g. 23.976 -> 25) to the timeline it's displayed in timeline text as "CLIPNAME (25.00 FPS)". Same for audio, till you alter the pan of the audio in the mixer, then the (25.00 FPS) hint disappears. Fortunately the audio speed does not change, it's only a labeling bug I guess.

    So wouldn't it be nice to convert before editing to the timeline?

    I tried to transcode the source clip with the option "convert to project frame rate". Nowhere I found information if this option referes to source clip settings "Playback frame rate". Sometimes the conversion is done without frame blending, sometimes not. I can't predict it. (again 23.976 -> 25)

    I think there are two options:
    1. get the timeline audio work right. When media composer transcodes a clip with speed altered source. The new created audio file has to have the same frame count.

    2. add an option to the consolidate/transcode. "convert to project frame rate" by what? preserve time (= frame blending) or preserve clean frames (= alter playback framerate like in the source settings)? And in case of altering playback framerate has the audio to be altered by speed change and pitch or by resampling and preserve pitch?

    Media Composer 8.8 Windows 10 Pro [view my complete system specs]
  • Thu, Sep 14 2017 10:52 AM In reply to

    • v-block
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    Re: discussion clean framerate conversion

    I don't have any experience of using AAF in the way you describe but if I was using for example a 23.976 clip in a 29.97 project, my preferred method would be to set the playback rate of the clip to 29.97 in the source settings, put the whole clip on the timeline, with audio. This of course will give me a quite fast playing video with the audio in sync but the pitch raised, so I would then apply a Timeshift filter from the AudioSuite and in the pitch controls input 80% and render, to take the audio pitch to the original. Then do a mix down and use that new clip  in the project.

    Of course speeding up the clip might look ridiculous, in which case messing around with the original video frames using suitable timewarp effects might be necessary but keeping the original video frames would be my preferred option.

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  • Fri, Sep 15 2017 1:29 AM In reply to

    • EvanAA
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    • Joined on Mon, Mar 7 2016
    • Posts 35
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    Re: discussion clean framerate conversion

    What I is create a project for the ALT framerates. Import into that project matching source and project framerate. Then when all done you can copy those bins into your master project and use them.

     

     

  • Mon, Sep 18 2017 3:32 PM In reply to

    Re: discussion clean framerate conversion

    zonik:

    I'd like to start a discussion about the framerate conversion within media composer. Especially when changing the source playback rate. What alters the speed, but does no frame-blending. Technically it's no conversion on the video side. Every frame in the source is one in the timeline. But on the audio side you have to change the speed.

    24.976 -> 25 fps = 95,904 % of original duration.

    The ability to mix framerates in the timeline is a good starting point. When editing a documentary in the PAL area (25p) I get a lot of clips by worldwide archives with different framerates. I link the footage or import it to DNxHR, keep the source framerate and edit it to my timeline, where the timewarp does his job to match the timeline framerate. It's a quick and dirty style. Of course you get interframe-blending (or stutter).

    When the source framerate and the timeline framerate are close, like 23.976 -> 25 it's a good way to alter the playback framerate in the clip's source settings. The clip duration alters as well, but you get a clean frame by frame result without frame-blending.

    And yes, audio is treated as well. But simply by playback speed. (=pitch shift) Not by resampling.

    Now the problems begin. When exporting an AAF to the record studio for mixing, media composer tumbles over it's own conversion. After AAF export the exported timeline has different durations than the original timeline. And some frame gaps. Same result when simply consolidate the timeline to another drive.

    Next point, when editing a source altered clip (e.g. 23.976 -> 25) to the timeline it's displayed in timeline text as "CLIPNAME (25.00 FPS)". Same for audio, till you alter the pan of the audio in the mixer, then the (25.00 FPS) hint disappears. Fortunately the audio speed does not change, it's only a labeling bug I guess.

    So wouldn't it be nice to convert before editing to the timeline?

    I tried to transcode the source clip with the option "convert to project frame rate". Nowhere I found information if this option referes to source clip settings "Playback frame rate". Sometimes the conversion is done without frame blending, sometimes not. I can't predict it. (again 23.976 -> 25)

    I think there are two options:
    1. get the timeline audio work right. When media composer transcodes a clip with speed altered source. The new created audio file has to have the same frame count.

    2. add an option to the consolidate/transcode. "convert to project frame rate" by what? preserve time (= frame blending) or preserve clean frames (= alter playback framerate like in the source settings)? And in case of altering playback framerate has the audio to be altered by speed change and pitch or by resampling and preserve pitch?

     

    I'm trying to learn some basics here, having moved only recently from v7 to v8.8.4/5:

    I will be doing some shooting, then editing on a 23.97 Project with several 23.97 cameras, but I will probably also need to include some other lockdown footage shot on consumer-variety (iPhone @24p, GoPro-like cameras @ 24p).

    I started testing some of this consumer gear at home on a v5.5.5 software-only system:

    I *thought* I saw some some frame-blended artifacts on some 4K-sized 24 FPS iPhone footage (from MoviePro+ App) which I had AMA-linked into a 23.976 Test project, then transcoded to same Project rate. The artifact looked like a shadow or something I could easily describe as partial frame blending. I was kind of surprised to see it given it was theoretically just 24P >> 23.976

    Question: What is the best way to introducing any objectionable Frame-blending artifacts from those kind of 24P  cameras?

    To start, I want to Group the lockdowns plus the other 23.97 camera files before editing (it is a simple 1 hour performance), but once I'm near a locked cut, I would not mind at all re-editing any frame-blended short lockdown cuts if it means I could replace those with non-blended versions.

    At the start of the project, which method (import or link) do I use to avoid "frame-blending", legacy or AMA with Source Settings/Playback Rate changed? If I am advised to open a seperate 24P Project, I'll do that to achive cleanest results.

    Thanks for any further suggestions.

    p.s. Is the smart move to open a seperate 24P Project for those consumer cameras, doing a AMA (or legacy Import). What is the next step? Is it Source Settings /Playback Rate change 24 to 23.976, then Group? Is it that simple now with v8.8.x?

    FYI, I'm not sure I'll even be showing faces with those lock-downs, but I am curious how to deal with audio sync if for some reason I am forded to use an extended on-face section. On this project, I will not be sending it out via AAF to a mixer.

     

    Win 7 Pro; HP 820z, 16GB ram; Composer Nitris DX, Squeeze v8.5 Pro _____ Also:___ Windows 7 Pro x64 Dell T3400 workstation E8400 3.0 Ghz 4GB Ram,... [view my complete system specs]
  • Mon, Sep 18 2017 5:06 PM In reply to

    Re: discussion clean framerate conversion

    If you bring any content into AVid that doesn't match the project frame rate exactly then Avid will use a motion adapter to allow that content to play at the project framerate. 24fps isn't 23.98fps so to play 24fps in a 23.98fps project the content has to be slowed down slightly.

    You can force the 24fps to play at 23.98 by changing the playback rate in the source settings to project rather than source clip. But it will then playback slower so you may have issues with sync.

     

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  • Mon, Sep 18 2017 6:28 PM In reply to

    Re: discussion clean framerate conversion

    Thanks for replying,Pat. I understand what you said. I guess Im asking how to avoid any motion-adapter "frame-blending" artifacts. I am willing to replace motion-adapted clips (after my rough edit from a Group Clip) with a slightly out of sync version. How would I do it is my question.

     

    Win 7 Pro; HP 820z, 16GB ram; Composer Nitris DX, Squeeze v8.5 Pro _____ Also:___ Windows 7 Pro x64 Dell T3400 workstation E8400 3.0 Ghz 4GB Ram,... [view my complete system specs]
  • Mon, Sep 18 2017 8:30 PM In reply to

    • v-block
    • Top 200 Contributor
    • Joined on Fri, Nov 4 2005
    • Posts 522
    • Points 6,605

    Re: discussion clean framerate conversion

    The options as far as I have understood them are

    You could start a 23.97fps project, link your 23.97fps and 24fps clips into that project but set the source playback rate of your 24fps clips to 23.97fps. That will keep the audio in sync, both the audio and video of the 24fps clips will be treated as 23.97fps (their duration will increase slightly but no frame blending will occur when output at 23.97fps. There will be a slight pitch change in the audio which you can address with an audio effect if necessary).

    You could start a 23.97fps project, link your 23.97fps and 24fps clips into that project and let MC automatically apply a timewarp effect to the 24fps clips when placed on the timeline (their duration will be the same as the original clips but there may be some frame blending or other artifacts, when output as 23.97fps, depending on which render 'Type' you choose in the  'Motion Effects Editor'. The audio will be in sync with no pitch change.)

    You could start a separate 24fps project but ultimately you would still need to bring the 24fps clips into the 23.97fps project as with the second option, which would eventually be output as 23.97fps. So unless you intend to use the clips in future 24fps projects, this could be considered a waste of time with regard to this project.

    One other option which is possible but maybe doesn't make much sense, certainly in your case is, You could start a 23.97fps project, link your 23.97fps and 24fps clips into that project and let MC automatically apply a timewarp effect to the 24fps clips when placed on the timeline. You could then remove the timewarp that would be automatically applied when cut to a sequence. This would, I think, throw your audio out of sync with the video and might cause other issues that are beyond me. So although it's an option I can't think of a reason to use it.

    Asus X58 Sabertooth motherboard, Core i7 920 CPU, Win 7 Pro 64bit, NVIDIA GeForce GT610, 12GB Corsair 3x4GB CMX-12GX3M3A1333C9 ram in triple channel config... [view my complete system specs]
  • Mon, Sep 18 2017 10:06 PM In reply to

    Re: discussion clean framerate conversion

    v-block:

    The options as far as I have understood them are

    You could start a 23.97fps project, link your 23.97fps and 24fps clips into that project but set the source playback rate of your 24fps clips to 23.97fps. That will keep the audio in sync, both the audio and video of the 24fps clips will be treated as 23.97fps (their duration will increase slightly but no frame blending will occur when output at 23.97fps. There will be a slight pitch change in the audio which you can address with an audio effect if necessary).

    You could start a 23.97fps project, link your 23.97fps and 24fps clips into that project and let MC automatically apply a timewarp effect to the 24fps clips when placed on the timeline (their duration will be the same as the original clips but there may be some frame blending or other artifacts, when output as 23.97fps, depending on which render 'Type' you choose in the  'Motion Effects Editor'. The audio will be in sync with no pitch change.)

    You could start a separate 24fps project but ultimately you would still need to bring the 24fps clips into the 23.97fps project as with the second option, which would eventually be output as 23.97fps. So unless you intend to use the clips in future 24fps projects, this could be considered a waste of time with regard to this project.

    One other option which is possible but maybe doesn't make much sense, certainly in your case is, You could start a 23.97fps project, link your 23.97fps and 24fps clips into that project and let MC automatically apply a timewarp effect to the 24fps clips when placed on the timeline. You could then remove the timewarp that would be automatically applied when cut to a sequence. This would, I think, throw your audio out of sync with the video and might cause other issues that are beyond me. So although it's an option I can't think of a reason to use it.

     

     

    Thanks, v-block, thats all very helpful, but I'll need to let it marinate in my gray matter for a bit. For my purposes, I intend to work with a 23.976 Group clip and use one wild sound audio source only. I will try out your three options- I'm more worried about ugly frame-blending artifacts than minor sync flaws since this is for the web anyway. (I feel I can probably slip picture into place or edit around any sync issues). To be continued.

    I learned yesterday that my iPhone 4k file stayed in sync with my crappy H1 zoom wav file within a quarter frame over the course of 1 hr, that's the good news for now.

    Thank you, all.

    Win 7 Pro; HP 820z, 16GB ram; Composer Nitris DX, Squeeze v8.5 Pro _____ Also:___ Windows 7 Pro x64 Dell T3400 workstation E8400 3.0 Ghz 4GB Ram,... [view my complete system specs]
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