Body: <p>I use a capture device from Atomos to capture video in ProRes format over HDMI. The issue is, this device will <em>only</em> capture video in the exact same frame rate as the HDMI signal's refresh rate. So a 60hz signal MUST capture to a 60fps file. There's no way to capture in 30fps mode, and no way to do IVTC for 24fps capture either, unless the source is 1080i (which is not useful for 4K capture).</p>
  <p>Since ProRes is an I-Frame only video format, I would imagine it <strong>should</strong> theoretically be possible to simply drop the unnecessary duplicated frames, spitting out a video that contains bit-identical frames, but uses much less storage. I capture both 30fps and 24fps content using this method, so it would be especially useful to me to be able to transfer that to my computer in a reduced file size, without any loss in quality.</p>
  <p>So how would I go about doing this? I plan to create a small app that will allow me to do this for every 30/24 fps capture I make, but my experience with ffmpeg is too limited to figure out exactly what command line to use for this problem.</p>
  <p>Note that the output frame rate should be exactly 50% of the input frame rate for 30fps sources, and exactly 40% of the input frame rate for 24fps sources . I can't work with variable frame rates, or frame rates that are slightly off from the standard rates. So ffmpeg should not be dropping any more extra frames than that, even if it decides they're duplicates.</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-06-01T13:34:09.307Z
Comments.Text: See https://stackoverflow.com/q/71029418/
Comments.UserDisplayName: Gyan
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-06-01T23:23:13.003Z
Comments.Text: @Gyan that looks promising, but I'm reading the documentation for those filters and I am really confused at how they work. Could you help suggest command line usage for my examples?
Comments.UserDisplayName: morphinapg
Tags: <ffmpeg><framerate><prores>
Title: ffmpeg: How to decimate frame rate without recompressing, for I-Frame only video, like ProRes?
UserDisplayName: morphinapg
ThreadText: # ffmpeg: How to decimate frame rate without recompressing, for I-Frame only video, like ProRes?
  
  (Asked by: username_0 on 2023-06-01)
  
  I use a capture device from Atomos to capture video in ProRes format over HDMI. The issue is, this device will *only* capture video in the exact same frame rate as the HDMI signal's refresh rate. So a 60hz signal MUST capture to a 60fps file. There's no way to capture in 30fps mode, and no way to do IVTC for 24fps capture either, unless the source is 1080i (which is not useful for 4K capture).
  
  Since ProRes is an I-Frame only video format, I would imagine it **should** theoretically be possible to simply drop the unnecessary duplicated frames, spitting out a video that contains bit-identical frames, but uses much less storage. I capture both 30fps and 24fps content using this method, so it would be especially useful to me to be able to transfer that to my computer in a reduced file size, without any loss in quality.
  
  So how would I go about doing this? I plan to create a small app that will allow me to do this for every 30/24 fps capture I make, but my experience with ffmpeg is too limited to figure out exactly what command line to use for this problem.
  
  Note that the output frame rate should be exactly 50% of the input frame rate for 30fps sources, and exactly 40% of the input frame rate for 24fps sources . I can't work with variable frame rates, or frame rates that are slightly off from the standard rates. So ffmpeg should not be dropping any more extra frames than that, even if it decides they're duplicates.
  
  **Tags:** ffmpeg, framerate, prores
  
  > **Comments:**
  > **username_1**: See https://stackoverflow.com/q/71029418/  
  > **username_0**: @username_1 that looks promising, but I'm reading the documentation for those filters and I am really confused at how they work. Could you help suggest command line usage for my examples?  
  
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  ## 0 answers
  
  