How to increase video speed and frame rate without duplicating frames

ffmpegframeratelibavvideo

I have a long video with a frame rate of 30 FPS that I want to convert into a 200x time-lapse with a frame rate of 60 FPS. My only problem is that avconv is unnecessarily duplicating every other frame in the output, making the 60 FPS output effectively 30 FPS. I want every frame to be unique. At a 200x speed increase and 2x frame rate increase, there is no reason to duplicate frames.

For example, the problem is that the output is using source frames like 1,1,21,21,41,41,… when I want it to use frames 1,11,21,31,41,51,…

Here's the command I'm using:

avconv -i input_30fps.avi -vcodec h264 -an -r 60 -vf "setpts=(1/200)*PTS" output_200x_60fps.avi

Best Answer

As happens regularly to me, after spending hours trying to figure it out before asking for help, I find the solution myself just minutes after asking.

It turns out avconv isn't the better replacement to ffmpeg that I thought it was when Linux Mint, IIRC, removed ffmpeg from the official repository in favor of avconv. Anyway, ffmpeg is back and I installed it and found the equivalent command that doesn't duplicate frames:

ffmpeg -i input_30fps.avi -vcodec h264 -an -vf "fps=60, setpts=(1/200)*PTS" output_200x_60fps.avi

Related Solutions

Convert high -speed video to normal by subsampling frames

If you want to keep real-time i.e. 1 second of live action is played out in 1 second of video then

ffmpeg -i input.mp4 -r 30 output.mp4

This will drop 3 out of every 4 frames.

If you want to preserve all frames but cycle through them slowly then

ffmpeg -i input.mp4 -vf setpts=4*PTS -r 30 output.mp4

FFmpeg – Reduce Video Frame Rate Without Dropping Useful Frames

I managed to fix my file. I found the mpdecimate filter, which drops duplicate or near duplicate frames from a video stream. First I tried:

ffmpeg -loglevel debug -i orig.mp4 -an -vf "mpdecimate" test.mp4

I added -loglevel debug to get more info during transcoding. The info showed what mpdecimate was doing with the frames, which was lots and lots of this pattern:

lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:44032 pts_time:3.44 drop_count:1
lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:44544 pts_time:3.48 drop_count:2
lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:45056 pts_time:3.52 drop_count:3
lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:45568 pts_time:3.56 drop_count:4
781>=hi keep pts:46080 pts_time:3.6 drop_count:-1
lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:46592 pts_time:3.64 drop_count:1
lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:47104 pts_time:3.68 drop_count:2
lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:47616 pts_time:3.72 drop_count:3
lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:48128 pts_time:3.76 drop_count:4
821>=hi keep pts:48640 pts_time:3.8 drop_count:-1
lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:49152 pts_time:3.84 drop_count:1
lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:49664 pts_time:3.88 drop_count:2
lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:50176 pts_time:3.92 drop_count:3
lo:0<217 lo:0<-2147483648 lo:0<-2147483648 drop pts:50688 pts_time:3.96 drop_count:4
793>=hi keep pts:51200 pts_time:4 drop_count:-1

I.e., it was consistently dropping 4 frames in a row as duplicates and keeping every 5th. This showed that the original frame rate was 1/5th of what it was now. I was lucky! Since the video's current 25 fps was a multiple of the original frame rate, there shouldn't be a problem with temporal misalignment of the kept and dropped frames. Therefore I retranscoded the original video with nothing more complex than -vf "fps=5", and the output seemed to be fine. Just to be sure, I piped the output through the mpdecimate filter, and it detected all remaining frames as a "keep". So the original file was not so messed up as I thought.

Best Answer

Related Solutions

Convert high -speed video to normal by subsampling frames

FFmpeg – Reduce Video Frame Rate Without Dropping Useful Frames

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