[FFmpeg-user] Replacing Specific Frames with Specific Other Frames

[Sam Logan]

On 5/7/14, Sam Logan <shapableline at gmail.com> wrote:
> I have a video file "Foobar.mp4" (stream 0 is a video stream, stream 1
> is an audio stream).
>
> My goal is to replace video frames 56-98 (a total of exactly 43
> frames) of the video with a back-and-forth loop of frames 46-55 (a
> total of 10 frames). In other words, I want to replace frames 56, 57,
> 58, ..., 98 in the video with this exact sequence of 43 frames:
>
> 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 47, 48, 49, 50, 51, 52, 53,
> 54, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 47, 48, 49, 50, 51, 52,
> 53, 54, 55, 54, 53, 52, 51, 50, 49
>
> (If the pattern is not clear, it first goes down to frame 46, then
> goes up to frame 55, and then repeats until we get to 43 frames.)
>
> Does anyone know how to write a filtergraph command that will
> accomplish this? Below, I detail my failed attempt.
>
> ****
>
> Anyway, my failed attempt: I tried using the overlay filter as
> follows. First, I extracted frames to PNGs:
>
> ffmpeg -t 00:00:10 -i "Foobar.mp4" "Frame%04d.png"
>
> Then I manually copied/renamed the PNGs for frames 46-55 so that they
> were in the order I gave above, giving them new filenames:
>
> Frame0001.png = frame 55
> Frame0002.png = frame 54
> ...
> Frame0043.png = frame 49
>
> and then deleted all other PNGs except for these 43 frames. Then I did:
>
> ffmpeg -i "Foobar.mp4" -i "Frame%04d.png" -filter_complex
> "[0:v][1:v]overlay=enable='between(n,56,98)'[out]" -acodec copy -map
> "[out]" -map 0:1 "FoobarEdited.mp4"
>
> But this did not work: frames 56-98 of "FoobarEdited.mp4" were indeed
> replaced, but all 43 frames were replaced with 43 copies of
> "Frame0043.png" instead of with what I was expecting: "Frame0001.png",
> "Frame0002.png", "Frame0003.png", etc.
>
> Does again, anyone know how to write a filtergraph command that will
> accomplish my goal? Thanks.
>

No one knows? Can anyone please help? Thanks.

Sam Logan