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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)

• create animated gif from video using ffmpeg and c#

  18 décembre 2019, par king

  I am trying to get animated gif from an video file.I cant create gif from below code. could any one help me in solving this problem.

        Process ffmpeg; // creating process
  
      string video;
  
      string thumb;
  
   //   string text = System.IO.File.ReadAllText(@"C:\xampp\htdocs\h\myText.txt");
  
      video = Page.MapPath("") + "\\o.avi";
  
      thumb = Page.MapPath("") + "\\output\\o.gif"; // thumb name with path !
  
      ffmpeg = new Process();
  
      int num = 3;
  
      int secpos = 1;
  
  
  
      // ffmpeg.StartInfo.Arguments = "ffmpeg -i o.avi -vf scale=320:-1,format=rgb8,format=rgb24 -t 10 -r 10 output.gif"; // arguments !
  
      ffmpeg.StartInfo.Arguments = " -i \"" + video + "\" -s 108*80 -ss " + secpos + " -t " + num + "\" -vf scale=320:-1,format=rgb8,format=rgb24 \"" + thumb + "\"";
  
      ffmpeg.StartInfo.FileName = Page.MapPath("ffmpeg//ffmpeg.exe");
  
      ffmpeg.Start(); // start !  

  I think there is a mistake in ffmpeg.StartInfo.Arguments .

• Command line ffmpeg, to insert part of a mp3 audio to another file

  14 janvier 2020, par tgkprog

  Want to copy from 3rd second of b.mp3 till 2:05 seconds of b.mp3 and append to the end of a.mp3 (its 3:23 long).

  Command :

  ffmpeg -i a.mp3 -i b.mp3

  Output :

  ffmpeg version 4.0.4-0ubuntu1 Copyright (c) 2000-2019 the FFmpeg developers   built with gcc 8 (Ubuntu 8.2.0-7ubuntu1)
  
    configuration: --prefix=/usr --extra-version=0ubuntu1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  
    libavutil      56. 14.100 / 56. 14.100
  
    libavcodec     58. 18.100 / 58. 18.100
  
    libavformat    58. 12.100 / 58. 12.100
  
    libavdevice    58.  3.100 / 58.  3.100
  
    libavfilter     7. 16.100 /  7. 16.100
  
    libavresample   4.  0.  0 /  4.  0.  0
  
    libswscale      5.  1.100 /  5.  1.100
  
    libswresample   3.  1.100 /  3.  1.100
  
    libpostproc    55.  1.100 / 55.  1.100
  
  Input #0, mp3, from 'a.mp3':
  
    Metadata:
  
      encoder         : Lavf58.12.100
  
    Duration: 00:02:48.00, start: 0.011021, bitrate: 144 kb/s
  
      Stream #0:0: Audio: mp3, 48000 Hz, stereo, fltp, 144 kb/s
  
      Metadata:
  
        encoder         : Lavc58.18
  
  Input #1, mp3, from 'b.mp3':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2mp41
  
      encoder         : Lavf58.12.100
  
    Duration: 00:01:33.02, start: 0.011995, bitrate: 117 kb/s
  
      Stream #1:0: Audio: mp3, 44100 Hz, stereo, fltp, 117 kb/s
  
      Metadata:
  
        encoder         : Lavc58.18
  
  At least one output file must be specified