Latest post Wed, Feb 17 2021 8:52 AM by Pat Horridge. 8 replies.
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  • Tue, Feb 16 2021 4:25 PM

    • Roger Owen
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    20 FPS Dilemma.

    I have a slightly unusual problem. I am currently working with some material transferred from 8mm cine film. Although scanned frame by frame – which would have given a 25 fps playback rate, the telecine transfer system creates an MP4 file with a playback rate of 20 fps and a frame size of 1440 x 1080. I can create a Custom pre-set to cater for the frame size but I cannot change the frame rate to 20 fps, so on playback at 25 fps there is a lot of jerkiness in movement and in panning shots, and stepping through frame by frame shows that there is some harsh interpolation going on – image ghosting between some frames, and image quality is poor. This does not happen in a variety of Media Players or Resolve. Anyone have any ideas how I can improve the quality in Media Composer.

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  • Tue, Feb 16 2021 4:43 PM In reply to

    • jakeheat
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    Re: 20 FPS Dilemma.

    If you're 8mm was shot at 20fps, have you tried importing this into a 60fps project. As a multiple of 20 it should give you even playback of you clip without interpolation. But you should probably ensure that the motion effect on your clip is playing back progressive, or both fields.

    Jake

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  • Tue, Feb 16 2021 6:01 PM In reply to

    Re: 20 FPS Dilemma.

    If the MP4 is supposed to be 25fps just make a 25fps project and AMA link the source in and then under source settings set the playback speed from Clip to project. It will now play the 20fps at 25fps (so it will be speeded up)

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  • Tue, Feb 16 2021 6:23 PM In reply to

    • jef
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    Re: 20 FPS Dilemma.

    In the original post the Roger stated that the file he recieved was given incorrect metadata of 20FPS.

    The simple fix for this is to bring the clip into a 25 fps timeline.  (He said it should have been 25fps).  Avid will put a motion adapter on the clip to "correct" the speed.  Promote this adapter and then set the speed to 100%.  The clip will now be playing frame for frame and at 25fps.

    Jef

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  • Tue, Feb 16 2021 6:36 PM In reply to

    • Roger Owen
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    Re: 20 FPS Dilemma.

    That's an idea, thanks Jake I'll give that a try.

    Avid Media Composer 2018.11, Kona 3, HP XW8600 2x3.16 Ghz Quad Zeon (X5460), 8 Gb RAM, Windows 7 Pro 64 bit. Nvidia GeForce GTX 560 Ti. [view my complete system specs]

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  • Tue, Feb 16 2021 6:57 PM In reply to

    • Roger Owen
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    Re: 20 FPS Dilemma.

    Thanks Pat, The MP4 file is 20fps (as far as my analysis software is concerned), even though the TK is scanning every frame. At first I thought that there was an algorithm in the MP4 file that was interpolating the frame rate back down to 20 fps, but going through the file in Resolve - there is no sign of interpolation, so what I'm thinking is that the Metadata is somehow commanding a playback rate of 20 fps..... how it's doing this is a bit beyond my personal knowledge base. I've spoken to the TK manufacturer, and they tell me that the reason they elected a playback rate of 20 fps is a compromise. Amateur cine film was shot at rates of between 16-18 fps for silent film and 24-25 fps for sound movies - so 20 fps sat in the middle. Within Avid I am using a 25FPS project, and AMA linking. My problem is the quality, not the speed. Somehow Avid is interpolating the footage and making it look really horrible. With Resolve I do not need to pre-establish project parameters - I guess it interrogates to Metadata during clip linking somehow. Anyway - the files look fine in Resolve, and for this project I might just have to work in DaVinci, although I'd prefer to work in Avid.

    Avid Media Composer 2018.11, Kona 3, HP XW8600 2x3.16 Ghz Quad Zeon (X5460), 8 Gb RAM, Windows 7 Pro 64 bit. Nvidia GeForce GTX 560 Ti. [view my complete system specs]

    Lots of kit... only one pair of hands!

  • Tue, Feb 16 2021 7:02 PM In reply to

    • Roger Owen
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    Re: 20 FPS Dilemma.

    Thanks Jef, Ah, maybe this motion adapter that Avid is putting on is the cause of my 'Quality' issue. The speed is fine, it's just the sudden appearance of very blocky interpolation artefacts that I'm concerned about.

    Avid Media Composer 2018.11, Kona 3, HP XW8600 2x3.16 Ghz Quad Zeon (X5460), 8 Gb RAM, Windows 7 Pro 64 bit. Nvidia GeForce GTX 560 Ti. [view my complete system specs]

    Lots of kit... only one pair of hands!

  • Tue, Feb 16 2021 9:05 PM In reply to

    • jef
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    Re: 20 FPS Dilemma.

    Roger Owen:

    Thanks Jef, Ah, maybe this motion adapter that Avid is putting on is the cause of my 'Quality' issue. The speed is fine, it's just the sudden appearance of very blocky interpolation artefacts that I'm concerned about.

    A motion adapter should not cause blocky images.  Only speed.

    Jef

    Avid DS 11.0.2 R.I.P | MC "Well, it depends ..." 2021 iMac w Big Sur [view my complete system specs]

    _____________________________________________

    Jef Huey

    Senior Editor

  • Wed, Feb 17 2021 8:52 AM In reply to

    Re: 20 FPS Dilemma.

    In an Avid 25fps project an AMA linked file (with source setting playback speed set to clip) will be interpolated from the clips fps metadata to 25fps.

    So Avid is trying to create 5 new frames every second from the 20 available.

     By default it either duplicates frames or creates blended frames (a superimposition of one frame ande another to create an inbetween frame)

    You can promote to fluid motion to get a better job but its a slow render process and results may need tweaking.

    However you look at it for a 25fps project you are needing 5 extra frames per second so it looks like Resolve does that better.

    You could always use resolve to make a new 25fps file and bring that into MC to cut.

    HP Z840 3.1GHZ 20cores 128GB RAM M4000 GPU 1TB NVMe drive HP Z book 17 G2 2.7GHZ Quad core 32GB RAM Nvidia K3100M 1TB SSD drive ACI Moderator. I'm... [view my complete system specs]

     

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    QC/QAR Training - Understanding Digital Media - Advanced Files * Compression - Avid Ingest - PSE fixing courses and more

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    T 07581 201248 | E pat@vet-training.co.uk | www.vet-training.co.uk|

     

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