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• How to use FFmpeg(v 4.0) HwAccell in Android

  21 novembre 2018, par 심상원

  I’m making an app that uses FFmpeg on Android to show the screen.

  I have a few questions to ask you.

  std::vector <avhwdevicetype> GetSupportHwDeviceType ()
  
  {
  
      unsigned int idx {};
  
      std::vector <avhwdevicetype> hwDevTypes;
  
  
  
      AVHWDeviceType hwDevType = AVHWDeviceType::AV_HWDEVICE_TYPE_NONE;
  
      while ((hwDevType = av_hwdevice_iterate_types (hwDevType)) ! = AVHWDeviceType::AV_HWDEVICE_TYPE_NONE)
  
      {
  
          __android_log_print (ANDROID_LOG_DEBUG, __func__, "[Index% d]", idx ++);
  
          __android_log_print (ANDROID_LOG_DEBUG, __func__,
  
                          "[Support Device Name% s]", av_hwdevice_get_type_name (hwDevType));
  
  
  
          hwDevTypes.push_back (hwDevType);
  
      }
  
  
  
      return hwDevTypes;
  
  }
  
  </avhwdevicetype></avhwdevicetype>

  I would like to use hardware acceleration with the above function, and as a result I could not find any type.

  At https://trac.ffmpeg.org/wiki/HWAccelIntro, it says that Android can use MediaCodec. Why can not I retrieve any type from Android NDK with GetSupportHwDeviceType () ?

  The Configure argument used while building FFmpeg for Android.

  --disable-asm
  
  --enable-cross-comile
  
  --disable-static
  
  --disable-programs
  
  --disable-doc
  
  --enable-shared
  
  --enable-protocol=file
  
  --enable-pic
  
  --enable-small
  
  --enable-mediacodec
  
  --enable-jni
  
  --enable-decoder=h264_mediacodec
  
  --enable-opengl
  
  
  
  /* The argument was not supported by ./configure --list-hwaccel in FFmpeg v4.0.3. */
  
  
  
  --enable-hwaccel=h264_mediacodec 

• ffmpeg - multiple output with thumbnails

  9 décembre 2016, par Thomas

  I would like ffmpeg to do the following :

  • read an input mp4 (-i movie.mp4)
  • skip the first 5 seconds (-ss 5)
  • find scene changes and display the frame numbers (-vf "select=gt(scene\, 0.4, showinfo))
  • output #1 - a gif file (output.gif)
  • output #2 - a contact sheet with all the thumbnails (-vf "select scale=320 :-1, tile=12x200" thumbnails.png)

  This will generate the thumbnails :

  ffmpeg -hide_banner -i d:/Test/movie01.mp4 -ss 5 -vf "select=gt(scene\,0.4), showinfo, scale=320:-1, tile=12x200" -vsync 0 thumbnails%03d.png

  this will generate the gif :

  ffmpeg -hide_banner -i d:/Test/movie01.mp4 -ss 5 -vf "select='not(mod(n,60))',setpts='N/(30*TB)', scale=320:-1" -vsync 0 output.gif

  I would like to do both at once with 2 more features :

  • set fps and resolution for the gif ; I would like the gif to represent the whole movie in X seconds, at Y fps (I know the duration of the input movie so I can calculate how often a frame needs to be captured)

  • set the width only for the thumbnail picture (tile=12 for example) and let ffmpeg determine the appropriate height

  I have tried to compose a command line from what I read on this page : https://trac.ffmpeg.org/wiki/Creating%20multiple%20outputs, using the split / map commands but I couldn’t get it to work

• Fast seeking ffmpeg multiple times for screenshots

  14 septembre 2021, par user3786834

  I have come across https://askubuntu.com/questions/377579/ffmpeg-output-screenshot-gallery/377630#377630, it's perfect. That has done exactly what I wanted.

  



  However, I'm using remote URLs to generate the screenshot timeline. I do know it's possible to fast seek with remote files using https://trac.ffmpeg.org/wiki/Seeking%20with%20FFmpeg (using -ss before the -i) but this only runs the once.

  



  I'm looking for a way to use the

  



  ./ffmpeg -i input -vf "select=gt(scene\,0.4),scale=160:-1,tile,scale=600:-1" \
-frames:v 1 -qscale:v 3 preview.jpg


  



  command but using the fast seek method as it's currently very slow when used with a remote file. I use PHP but I am aware that a C method exists by using av_seek_frame, I barely know C so I'm unable to implement this into a PHP script I'm writing. So hopefully, it is possible to do this directly with ffmpeg in the PHP system() function.

  



  Currently, I run seperate ffmpeg commands (with the -ss method) and then combine the screenshots together in PHP. However, with this method it will be refetching the metadata each time and a more optimized method would be to have it all happen in the same command line because I want to reduce the amount of requests made to the remote url so I can run more scripts in sequence with each other.

  



  Thank you for your help.