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• Is there a way to eliminate seek time when decoding part of a video using ffmpeg ?

  17 décembre 2019, par Babis

  I’ve got some MKV videos encoded with FFV1. For each of the frames, I want to run some complex and time-intensive python or matlab code, so I’m using multithreading, where each thread works on an individual image.

  I’ve tried extracting a single frame from the video using -ss, but it’s terribly inefficient.

  The most efficient way is to decompress everything into images in one go, but then I’m writing to disk, and then I’ll be reading from disk, therefore it’s not ideal either.

  I’ve tried using a ram disk to export images to, and reading them from python/matlab, but it’s not great performance-wise either. Also, I have to split the export into several batches, as the video file is 20GB and all of the exported images will not fit into memory

  Is there a way to rapidly extract individual frames from ffmpeg directly into RAM (or ram disk), so that they can be used by another program ? For example using something like a lookup-table.

  For reference, each video is about 20GB, comprised of 50000 frames, and they are all keyframes (it’s for archival purposes)

• ffmpeg use complex_filter with alphamerge only for a part of the video

  7 mars 2019, par Andy P

  I am trying to apply a filter to only the first few seconds of a video clip - and leave the rest of the video unchanged.

  why ?
  I got some video clips that I wanted to put on a website - unfortunatelly those clips are starting with a black background, which does not fit the website’s design. Therefor I was changing the background to transparent.

  I got that filter working from many of the great answers here (thanks to Gyan) and those videos are playing fine in common browsers :

  ffmpeg -i ${1} -filter_complex "[0]split[m][a];
  
  [a]geq='if(lt(lum(X,Y),16),0,255)',hue=s=0[al];
  
  [m][al]alphamerge,format=yuva420p" -c:v libvpx-vp9 -b:v 0 -crf 18 -an -auto-alt-ref 0 ${1}.webm

  the problem now : of course this replaces all black pixels during the video, which leads to many artefacts later on. Therefor I am searching for a way to apply that filter only to the first 5-ish seconds.

  I think I need a second split and a crop or a trim and a concat filter with a timestamp - but I can’t make it work :(

  ffmpeg -i ${1} -filter_complex "[0]split[f][s];
  
  [f]trim=start=0,duration=5[ft];
  
  [s]trim=start=6[st];
  
  [st]split[m][a];
  
  [a]geq='if(lt(lum(X,Y),16),0,255)',hue=s=0[al];
  
  [m][al]alphamerge,format=yuva420p[mal];
  
  [ft][mal]concat" -c:v libvpx-vp9 -b:v 0 -crf 18 -an -auto-alt-ref 0 ${1}.webm

  /edit : I am changing the subject slighty, to reflect the actual problem.

• youtube-dl, is there a way to extract the "specific format" video URL ? [closed]

  29 juillet 2020, par karma

  Following my question before in this link,
  
It seems that the copied version is from the highest resolution format, as the resulting video portion is 1920x1080 resolution.

  


  The available format :

  


  C:\Standalone Program\YoutubeDL>youtube-dl -F https://www.youtube.com/watch?v=kGDgGsrA78s
[youtube] kGDgGsrA78s: Downloading webpage
[info] Available formats for kGDgGsrA78s:
format code  extension  resolution note
249          webm       audio only tiny   52k , opus @ 50k (48000Hz), 7.49MiB
250          webm       audio only tiny   65k , opus @ 70k (48000Hz), 9.45MiB
251          webm       audio only tiny  114k , opus @160k (48000Hz), 17.07MiB
140          m4a        audio only tiny  164k , m4a_dash container, mp4a.40.2@128k (44100Hz), 21.06MiB
278          webm       256x144    144p  103k , webm container, vp9, 30fps, video only, 15.78MiB
160          mp4        256x144    144p  117k , avc1.4d400c, 30fps, video only, 12.96MiB
242          webm       426x240    240p  231k , vp9, 30fps, video only, 33.40MiB
133          mp4        426x240    240p  254k , avc1.4d4015, 30fps, video only, 25.10MiB
243          webm       640x360    360p  420k , vp9, 30fps, video only, 60.81MiB
134          mp4        640x360    360p  652k , avc1.4d401e, 30fps, video only, 61.92MiB
244          webm       854x480    480p  781k , vp9, 30fps, video only, 105.14MiB
135          mp4        854x480    480p 1190k , avc1.4d401f, 30fps, video only, 114.76MiB
247          webm       1280x720   720p 1550k , vp9, 30fps, video only, 211.07MiB
136          mp4        1280x720   720p 2383k , avc1.4d401f, 30fps, video only, 213.18MiB
248          webm       1920x1080  1080p 2752k , vp9, 30fps, video only, 408.32MiB
137          mp4        1920x1080  1080p 4443k , avc1.640028, 30fps, video only, 435.80MiB
18           mp4        640x360    360p  640k , avc1.42001E, 30fps, mp4a.40.2@ 96k (44100Hz), 106.07MiB (best)


  


  So after I do :

  


  youtube-dl -g https://www.youtube.com/watch?v=kGDgGsrA78s


  


  and the video URL result :

  


  https://r2---sn-uigxxi0ujipnvo-q2ne.googlevideo.com/videoplayback?expire=1596034295&ei=lzghX6SHKMOD8QPlx5SQBw&ip=223.255.228.87&id=o-AK6cYo88zJXe5Xb4y1QsXspuRnVCy-zPFpMaHcAaTQ-_&itag=137&aitags=133%2C134%2C135%2C136%2C137%2C160%2C242%2C243%2C244%2C247%2C248%2C278&source=youtube&requiressl=yes&mh=DA&mm=31%2C29&mn=sn-uigxxi0ujipnvo-q2ne%2Csn-npoe7nlz&ms=au%2Crdu&mv=m&mvi=2&pl=24&initcwndbps=173750&vprv=1&mime=video%2Fmp4&gir=yes&clen=456970484&dur=1389.955&lmt=1521825834085900&mt=1596012582&fvip=5&keepalive=yes&fexp=23883098&c=WEB&sparams=expire%2Cei%2Cip%2Cid%2Caitags%2Csource%2Crequiressl%2Cvprv%2Cmime%2Cgir%2Cclen%2Cdur%2Clmt&sig=AOq0QJ8wRgIhAMvZrHYvC1YrkvtARzhjyD8dnMnlefobGrOFM1rX6QZPAiEAqqeIsKdZ19y-SlHf-l8YwTx2yYbo1p5sFlVoC87oXEQ%3D&lsparams=mh%2Cmm%2Cmn%2Cms%2Cmv%2Cmvi%2Cpl%2Cinitcwndbps&lsig=AG3C_xAwRAIgAIwAVMPrcMhAL476uN_ZzWj8vKPGGW58KCpHBYBsKeICICRgVWgthNvgbGl8VgQwscjJ0n8ib4XBNjRxRgSg2T5r&ratebypass=yes


  


  I think the URL is for :

  


  137          mp4        1920x1080  1080p 4443k , avc1.640028, 30fps, video only, 435.80MiB


  


  Since I want a smaller file size, I wonder if it's possible to get the video URL (for example) for :

  


  243          webm       640x360    360p  420k , vp9, 30fps, video only, 60.81MiB


  


  So then later when I feed the URL to ffmpeg to extract some portion of that lower quality video URL, the result has a smaller file size.

  


  Any kind of help would be greatly appreciated.
Thank you in advanced.

  


  BTW, I use Windows 10 command prompt (administrator).