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• ffmpeg : how to extract keyframes from certain time ranges into filenames with timestamps from the original video ?

  18 mai 2023, par Display Name

  I have as input specific timestamps I'm interested in, and I wish to extract keyframes closest to them. I thus use skip_frame nokey and a select='between(t,...,...)+between(t,...,...)+...' where I add a few seconds around each time I'm interested in (enough so that at least one keyframe will fall in that range based on the input video I have, and then can manually delete if more than one came out in a given time range in my sequence). Chaining the between()s lets me use a single command to extract all of these images in order to avoid seeking from the beginning of the video for each image, were I to use separate command per image. So this part works fine.

  


  The problem is that I want the output image filenames to correspond to the timestamps, in seconds (or some decimal fraction of seconds like tenths or milliseconds) of the extracted frames with respect to the INPUT video. With older versions of ffmpeg, I used to be able for example to get output filenames being times in terms of tenths of a second with -vsync 0 -r 10 -frame_pts true %05d.webp but with recent versions, that results in the error One of -r/-fpsmax was specified together a non-CFR -vsync/-fps_mode. This is contradictory. Replacing the deprecated -vsync with -fps_mode and one of the CFR values results in ffmpeg DUPLICATING frames to fulfill the specified -r value which results in a huge number of output images. The way I am able to get just the set of keyframes I want and no duplications is to drop the -r and use -fps_mode passthrough, but then I lose the naming of the output files by their time in the original video. Searching around here and elsewhere on the web, I have tried things like setting settb=...,setpts=... and -copyts but in the end couldn't get it to work.

  


  As a complete example, the command
ffmpeg -skip_frame nokey -i "input.mp4" -vf "select='between(t,15,25)+between(t,40,50)+between(t,95,105)+between(t,120,130)+between(t,190,200)',scale='min(480,iw)':-2:flags=lanczos" -fps_mode passthrough -copyts -c:v libwebp -quality 75 -preset photo -frame_pts true %05d.webp gives me the right set of output images, but not the filenames that would make it easy for me to quickly manually find frames corresponding to specific times in the original video.

  


• ffmpeg extract keyframes from certain time ranges to filenames with timestamps from original video

  17 mai 2023, par Display Name

  I have as input specific timestamps I'm interested in, and I wish to extract keyframes closest to them. I thus use skip_frame nokey and a select='between(t,...,...)+between(t,...,...)+...' where I add a few seconds around each time I'm interested in (enough so that at least one keyframe will fall in that range based on the input video I have, and then can manually delete if more than one came out in a given time range in my sequence). Chaining the between()s lets me use a single command to extract all of these images in order to avoid seeking from the beginning of the video for each image, were I to use separate command per image. So this part works fine.

  


  The problem is that I want the output image filenames to correspond to the timestamps, in seconds (or some decimal fraction of seconds like tenths or milliseconds) of the extracted frames with respect to the INPUT video. With older versions of ffmpeg, I used to be able for example to get output filenames being times in terms of tenths of a second with -vsync 0 -r 10 -frame_pts true %05d.webp but with recent versions, that results in the error One of -r/-fpsmax was specified together a non-CFR -vsync/-fps_mode. This is contradictory. Replacing the deprecated -vsync with -fps_mode and one of the CFR values results in ffmpeg DUPLICATING frames to fulfill the specified -r value which results in a huge number of output images. The way I am able to get just the set of keyframes I want and no duplications is to drop the -r and use -fps_mode passthrough, but then I lose the naming of the output files by their time in the original video. Searching around here and elsewhere on the web, I have tried things like setting settb=...,setpts=... and -copyts but in the end couldn't get it to work.

  


  As a complete example, the command
ffmpeg -skip_frame nokey -i "input.mp4" -vf "select='between(t,15,25)+between(t,40,50)+between(t,95,105)+between(t,120,130)+between(t,190,200)',scale='min(480,iw)':-2:flags=lanczos" -fps_mode passthrough -copyts -c:v libwebp -quality 75 -preset photo -frame_pts true %05d.webp gives me the right set of output images, but not the filenames that would make it easy for me to quickly manually find frames corresponding to specific times in the original video.

  


• Is there any way to have a number of video feeds cycle in rotation with ffmpeg ?

  1er novembre 2020, par Brennan

  Is there any way I could take, lets say, 4 live video streams and have them cycle in a rotation on the screen ? I want to take a video feed and play, wait for 5 seconds, go to next video feed, wait 5 seconds, etc...Below is the actual ffmpeg command I want to use and the only idea I have thus far is :

  


  for rotation in $source4 $source5 $source6 $source7; do
    ffmpeg -rtsp_transport tcp -stimeout 100 -i $source1\
           -rtsp_transport tcp -stimeout 100 -i $source2\
           -rtsp_transport tcp -stimeout 100 -i $source3\
           -rtsp_transport tcp -stimeout 100 -i $rotation\
           -filter_complex "nullsrc=size=3840x2160 [base];\
           [0:v] setpts=PTS-STARTPTS [upperleft];\
           [1:v] setpts=PTS-STARTPTS [upperright];\
           [2:v] setpts=PTS-STARTPTS [lowerleft];\
           [3:v] setpts=PTS-STARTPTS [lowerright];\
           [base][upperleft] overlay=shortest=1 [tmp1];\
           [tmp1][upperright] overlay=shortest=1:x=1920 [tmp2];\
           [tmp2][lowerleft] overlay=shortest=1:y=1080 [tmp3];\
           [tmp3][lowerright] overlay=shortest=1:x=1920:y=1080"\
           -c:v h264_nvenc -preset llhq -f matroska - | ffplay -
           sleep 5
    done


  


  As you can see, this would not be very efficient or even usable considering how long it takes to get everything going. If anyone has any ideas I would appreciate it. I am only fluent in Linux shell scripting (Bash) so any other language would be out of my reach at this time. I am defiantly open to suggestions for other tools or frameworks to try. The main goal is to make a script for a group of security cameras with one in the mosaic that rotates through all the additional camera feeds that do not include the 3 already on the screen. It needs to be as low maintenance as possible i.e. a network issue drops connection it should automatically keep checking for connectivity and restart when established. I can do this in a Bash script very easily but getting the videos all up on screen is been a challenge. I considered making completely separate invocations of ffplay for each feed then using wmctrl or similar to arrange them on screen but I am still left with the issue of restarting the rotating one all the time.