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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)

• Parsing An ArrayList of BufferedImages From FFmpeg

  4 juin 2015, par user3725743

  I am using FFmpeg in my java app to turn a video into an ArayList of BufferedImages. Im am using this code to split a video file into individual jpg frames :

  builder.command(FFmpeg, "-i", "<video url="url">", "-vf", "fps=5,scale=128:128,format=rgb8,format=rgb24", "out%d.jpg");
  
  </video>

  This produces a folder full of jpg frames, it works fine. But I would rather not write them to individual files, I would rather make that output turned into an ArrayList of BufferedImages, WITHOUT having to write each frame to a seperate file.

  This should be what the command line would look like for the above code :

  FFmpeg.exe -i <video url="url"> -vf fps=5,scale=128:128,format=rgb8,format=rgb24 out%d.jpg
  
  </video>

  If its not possible to parse the ArrayList directly, what other solutions do I have which would be more elegant ?

• ffmpeg shell script globbing

  10 novembre 2015, par AD0AE

  I have a pretty straight forward question. I have a bunch of individual directories that are labeled as ./001 ./002 ... ./201
  within each directory contains files that have the identifier *_IO.PNG

  I can use the shell command : ffmpeg -framerate 20 -pattern_type glob -i './066/*IO.PNG' -c:v libx264 -pix_fmt yuv420p 066.mp4 and this works great. It does exactly what I want.

  However, I tried to write a shell script, which is below but this does not work. It seems to be loading individual files instead of all of them at once. Any help would be appreciated.

   #!/bin/bash
  
   for i in {1..5}
  
   do
  
     FILE=$(printf %03d $i)
  
     echo " This file: $FILE"
  
     infile='./$FILE/*IO.PNG'
  
     echo $infile
  
     ffmpeg -framerate 20 -pattern_type glob -i $infile -c:v libx264 -pix_fmt yuv420p './$FILE.mp4'
  
   done