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• Rendering images starting from the last image

  5 juillet 2016, par M.M

  I have a series of images (named : example001.jpg to example100.jpg) and I want to output a video for these images starting from the last picture and back to the first one (i.e., in descending order).
  I use the folloing command :

  ffmpeg -r 10 -i example%03d.png -start_number 100 output.mp4

  But, the output video is not showing the desired video.
  What is wrong in the used command ?

• FFMpeg Commands definition in library source code

  25 janvier 2013, par SKC

  I tried running the ffmpeg commands from Android activity using an emulator in Windows OS, but i get errors.
  I tried keeping both my resource files in /mnt/sdcard as well the application package within /data/data, but none of the options worked out for running the ffmpeg commands.

  These are the following approach i had taken while running the command through an android activity.
  (Command to convert a series if images into a video)
  Approach 1 :

      String[] cmd =new String[4];
  
      cmd[0]="/data/data/com.example.commandlineffmpeg/files/ffmpeg";
  
      cmd[1]="-i";
  
      cmd[2]="/data/data/com.example.commandlineffmpeg/images/bpc_%03d.png";
  
      cmd[3]="/data/data/com.example.commandlineffmpeg/out/out.avi";
  
  
  
      Process p = Runtime.getRuntime().exec(cmd, null, new File("/data/data/com.example.ffmpegnew/out"));

  I have solved this, basically there was system permission issues and hence we were not allowed to access the system properties required to run the FFMpeg commands.
  Thus we need to sign the apps with the system certificates and hence we can use FFMpeg commands directly from any android activity.

• FFMPEG x264 encoding on Android - error with lookahead

  6 janvier 2013, par Tishu

  I am using FFMPEG + x264 on Android to encode YUV420 frames to a video file. I use the following code on each frame to encode them :

  avcodec_encode_video2(gVideoWriteCodecCtx, &packet, pCurrentFrame, &gotPacket);

  On the first few calls, the frame buffer gets filled and nothing is encoded. When the first encoding happens, a call is made to x264_lookahead_get_frames. I can see there that my frame array is correctly populated, but the first item is NULL. As a consequence, in x264_weights_analyse the reference frame gotten as frames[p0] is NULL and I get an exception there.

  slicetype.c, the first frame in "frames" is NULL

  if( h->param.analyse.i_weighted_pred && b == p1 )
  
      {
  
          x264_emms();
  
          x264_weights_analyse( h, fenc, frames[p0], 1 );
  
          w = fenc->weight[0];
  
      }

  And the exception happens there, ref is NULL

  static void x264_weights_analyse( x264_t *h, x264_frame_t *fenc, x264_frame_t *ref, int b_lookahead )
  
      {
  
          int i_delta_index = fenc->i_frame - ref->i_frame - 1;

  I surely am missing something as I am sure this encoder works for most people :) Does anyone have an idea why this first frame in the "frames" array is null ?

  Many thanks