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• Yes or no, will ffmpeg api do hardware decoding on iOS ?

  15 janvier 2019, par Fattie

  There seems to be conflicting information on this.

  https://trac.ffmpeg.org/wiki/HWAccelIntro

  notice the first diagram, it firmly marks iOS as “Y” on VideoToolbox

  

  however in the comments down the bottom it says

  VideoToolbox. ​VideoToolbox, only supported on macOS. H.264 decoding is available in FFmpeg/libavcodec.

  And in the confusing second diagram it says "Standalone" is not done for VideoToolbox.

  We have found that using ffmpeg compiled in to iOS .... it seems to not use hardware decoding, which is really a pain.

  1. With avcodec_get_hw_config() we get AV_PIX_FMT_VIDEOTOOLBOX, AV_HWDEVICE_TYPE_VIDEOTOOLBOX which is seemingly correct.

  2. But usage and framerates clearly shows everything is being done in CPU. The code is in ff_hevc_hls_residual_coding all the time. (That’s fffmpeg’s software decoder.)

  3. This very diff very long git.videolan.org URL here seems to suggest again it should all be working.

  4. Have tried every iPhone etc. of course

• ffmpeg-Error "Buffer queue overflow, dropping." when merging two videos with delay

  20 septembre 2016, par Stefan Urbansky

  I want to merge two videos (as example the iphone video from https://peach.blender.org/trailer-page/). The videos are placed on an background image with the overlay filter and the second video starts 3 seconds later.

  And I need that the audio is mixed.

  Here is my code :

  ffmpeg \
  
      -loop 1 -i background.png  \
  
      -itsoffset 0  -i trailer_iphone.m4v \
  
      -itsoffset 3  -i trailer_iphone.m4v \
  
      \
  
      -y \
  
      -t 36 \
  
      -filter_complex "
  
          [2:a] adelay=3000 [2delayed];
  
          [1:a][2delayed] amerge=inputs=2 [audio];
  
          [0][1:v] overlay=10:10:enable='between(t,0,33)' [lv1];
  
          [lv1][2:v] overlay=10:300:enable='between(t,0,36)' [video]
  
      " \
  
      \
  
      -threads 0 \
  
      -map "[video]" -map "[audio]" \
  
      -vcodec libx264 -acodec aac \
  
      merged-video.mp4

  I get the error message :

  [Parsed_overlay_3 @ 0x7fe892502ac0] [framesync @ 0x7fe892502b88] Buffer queue overflow, dropping.

  And the merged video has many dropped frames.

  I know that are some other posting with this error message. But the suggested solutions doesn’t work for me.

  How can I fix the problem ?

• CVOpenGLESTextureCacheCreateTextureFromImage from uint8_t buffer

  6 novembre 2015, par resident_

  I’m developing an video player for iPhone. I’m using ffmpeg libraries to decode frames of video and I’m using opengl 2.0 to render the frames to the screen.

  But my render method is very slowly.

  A user told me :
  iOS 5 includes a new way to do this fast. The trick is to use AVFoundation and link a Core Video pixel buffer directly to an OpenGL texture.

  My problem now is that my video player send to render method a uint8_t* type that I use then with glTexSubImage2D.

  But if I want to use CVOpenGLESTextureCacheCreateTextureFromImage I need a CVImageBufferRef with the frame.

  The question is : How I can create CVImageBufferRef from uint8_t buffer ?

  This is my render method :

  - (void) render: (uint8_t*) buffer

  
  NSLog(@"render") ;

  [EAGLContext setCurrentContext:context];
  
  
  
  glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebuffer);
  
  glViewport(0, 0, backingWidth, backingHeight);
  
  
  
  glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
  
  
  
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  
  
  
  // OpenGL loads textures lazily so accessing the buffer is deferred until draw; notify
  
  // the movie player that we're done with the texture after glDrawArrays.         
  
  glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, mFrameW, mFrameH, GL_RGB,GL_UNSIGNED_SHORT_5_6_5, buffer);   
  
  
  
  glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
  
  
  
  [moviePlayerDelegate bufferDone];
  
  
  
  glBindRenderbuffer(GL_RENDERBUFFER, colorRenderbuffer);
  
  [context presentRenderbuffer:GL_RENDERBUFFER];

  Thanks,