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• ffmpeg : is there a fast way for extracting several thumbnails from a video without parsing the video from the beginning every time ?

  18 mars, par archie

  I tried several ways for extracting sample frames from a video file with ffmpeg. I found out that the fastest way is by placing the following command in a loop :

  


  ffmpeg -ss $frame_time -i "$input_video" -frames:v 1 -vf scale=256:-1 "$Work_dir/thumb$thumb_index.jpg"


  


  (I have omitted the parts of the command that are not relevant to the question, such as drawtext, hide_banner, loglevel). The variables frame_time and thumb_index are initialized before the loop and incremented by a fixed amount at every step : +1 for thumbs_index and $duration/25 for frame_time. I read in the ffmpeg documentation (https://trac.ffmpeg.org/wiki/Seeking) that having the -ss part before the -i part is very fast because the input is parsed by keyframe. For the same reason, the loop containing the command above is also much faster than commands based on "-vf fps=$thumbs_number/$duration".

  


  In fact, the code works pretty well. However, I can't escape a feeling of programming discomfort, because ffmpeg is called several times for each video file, and every time it has to parse the file from the beginning. I mean, if I had a function doing the same as the command above — it would parse a video from the beginning to search for a frame at a certain time — calling it n times to extract a regular sequence of n frames would be bad programming. I should change the function to parse the video file once and get all the frames I need in a single pass.

  


  My question is : is there a fast way for having ffmpeg parse a video file a single time, searching by keyframes and extracting a given number of frames at a given distance from one another ? I am ready to take No for an answer, but one who is deeper into ffmpeg than I am might know a way. Thanks

  


• Seeking issues on larger video files on HTML page (ffmpeg)

  5 juillet 2023, par Xenons

  After testing out numerous of "html video players" and even making our own making sure to wait for events such as player.oncanplaythrough to fire before even attempting to start videos
we've had the same issue for months now.

  


  Mainly we offer 3 resolutions for same video (720, 1080, 4k)
and out of the 3, 2 have the seeking issue where trying to skip to any time or even trying to fast forward by x amount of seconds with arrow keys would just bring the video back to 00:00 time
this only happens on 1080 and 4k resolutions and after refreshing the page it just works as normal afterwards

  


  we've tried pretty much anything we could think of to combat this but with no luck

  


  ffmpeg line for 1080 and 4k (these files are webm but same happened for mp4 on these resolutions with same encoding)

  


  -c:v libvpx-vp9 -pix_fmt yuv420p -crf 24 -b:v 0 -c:a libopus -b:a 128k -movflags +faststart


  


  ffmpeg line for 720 (mp4 file)

  


  -c:v libx264 -preset slow -pix_fmt yuv420p -crf 20 -b:a 128k


  


  To be quite frank at this point I am at a loss and without many ideas left so I am turning to stack overflow in case someone might have an idea on what would cause this

  


  I am contemplating to attempt perhaps loading videos as blobs and playing them that way, not sure if this would fix it but it does bring the load times up drastically so I would save it as last resort

  


  Thus far I have tried two html video players (plyr and videojs) and after that I just wrote my own "player"
of course it's just regular html and js but that's what makes me even more confused as there is nothing that should hinder the files in any way from working as intended

  


  we've also tried changing ffmpeg encoding a few times but to no avail either.

  


  EDIT :
The issue was caused by cloudflare caching, we simply made two rules to exclude webm and mp4 url's from being cached and that completely fixed all of our seeking issues

  


• Converting MPD (MPEG-DASH) stream to m3u8

  1er avril 2023, par veedoni

  I am currently doing research about how to convert MPEG-DASH stream to m3u8. So far I couldn't find anything helpful. What I know is that I need to decrypt mpd file using license key which I have and then convert it to m3u8. I have tried multiple times in last 7 days to do this but unsuccessful. I was using axios along with crypto, fetch, xml2js, m3u8stream and a lot of others tools. I am looking for directions where to start and examples of what to do because I feel like I'm lost. Anything would be helpful, Thanks !