vf "bwdif=0,select='between(mod(n\,$ips)\,1\,2)'" - $ips is images per second Here is my call w/a filter that works correctly for progressive video source : ffmpeg -i $infile -vf "select='if(eq(n\,0),1,floor(t)-floor(prev_selected_t))" -vsync 0 $outfilethe following still return only half-height images for interlaced source. I've chosen an endpoint 0.5 seconds greater than the start point under the assumption that the video is 30 frames per second. i've tried various combinations of deinterlacing (`yadif/bwdif`) with `select` but the filter chains i create either cause errors or still return a half-sized image. ffmpeg -i inVideo.mp4 -vf 'select'between(t,30,30.5)+between(t,45,45.5)+between(t,73,73.5)'' -s 320x240 -vsync 0 outd.png The select filter expression selects all frames in each of the three ranges. my script works ok if the video is progressive, but doesn't work so well for interleaved video (only the first field is output in that case, creating a half-height image). Where total number of select clauses is equal to the number of frames needed from each set of X frames.I'm trying to write a shell script to analyse some videos by using the first frame of each second of video as a basis. You can use the offset device n+c or n-c if one of the denominators is a multiple of the others.Ī cruder way to do this is ffmpeg -i in.mp4 -vf select='not(mod(n,12))+not(mod(n+3,12))+not(mod(n+5,12))+not(mod(n+7,12))+not(mod(n+11,12))` -vsync 0 frames%d.jpg
#Ffmpeg extract frames time range mp4
The idea is to represent your frequency as a sum of reciprocals, 1/f = 1/m + 1/n + 1/p. I am trying to convert a MP4 video file into a series of jpg images (out-1.jpg, out-2.jpg etc.) using FFMPEG with, mkdir frames ffmpeg -i '1' -r 1 frames/out-03d. Since, in this case, the latter will coincide with the former selection, we can pick one frame earlier i.e. You can decompose that as 1 out of 3 + 1 out of 12. So that means you need 5 frames from every 12. Let's take f = 2.4 which is the same as 12/5. There is a way to do this directly with select filter if you can decompose the frequency into a rational number (and do a bit of maths). If you have a list of frames, you can just run ffmpeg -i in.mp4 -vf select='eq(n,5)+eq(n,11)+eq(n,15).' -vsync 0 frames%d.jpg Then am I able to pass that (the frames list) into the ffmpeg command? Or can I tell ffmpeg to do something similar? So that means you need 5 frames from every 12.
to get the frames I would do something like this: nframes = 72 # number of frames in video
Maybe I could use a for loop to generate a list of the frames closest to the desired interval and then pass that in as the select filter?Į.g. Once you have your video files on your Pi, it is time to get down to coding.
Whats the best way to get exactly 30? - obviously the interval wouldn't be identical but thats fine. The -startnumber#Ffmpeg extract frames time range mod
I think the mod has to be an integer (?) so I could either round down and use 2 which gives me 36 images or round up which gives me 24 images I'm running this from a python script so i'm doing something like the following for the filter: select='not(mod(n\," + str(mod) + "))' Then run it as follows FFmpeg -ss 4.6 - i input.mp4 c : v libx264 -c : a aac -frames : v 60 out.mp4. That would be 138/30 4.6 Next, encode a specific number of frames, using the -frames: v. ffmpeg -i -ss 00:23:00 -frames:v 1 out2.jpg This example will also produce one image frame (out2. The flags can be found here : AVSEEKFLAGBACKWARD. Searches by time previous key frame within the specified AVStream index. int avseekframe(AVFormatContext s, int streamindex, int64t timestamp, int flags) Seek to the keyframe at timestamp. mp4 The constant frame rate cures the issues mentioned above. I've tried using the 'select' with 'mod' but if the total number of frames does not fit neatly into the desired number of images (30) then I sometimes end up with more images, sometimes less.įor example if my video is 72 frames long, my 'mod' would be 72 / 30, which is 2.4. So, for a video that is at 30 fps, and you wish to start at 138 frames, divide the frames with the fps to get the timestamp. Answer: Found: FFmpeg Docs or Libav Docs. In this part 1 of FFmpeg encoding comparisons I look at x264 presets. I want to create a maximum of 30 images from a video (and tile them for a sprite sheet).
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