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• OpenGL ES glReadPixels exc_bad_access

  6 décembre 2011, par Yanny

  I'm trying to create video from images using OpenGL ES and ffmpeg, but on iPad(4.3) I have a crash on glReadPixels

  -(NSData *) glToUIImage {
  
  
  
      int numberOfComponents = NUMBER_OF_COMPONENTS; //4
  
      int width = PICTURE_WIDTH; 
  
      int height = PICTURE_HEIGHT;
  
  
  
      NSInteger myDataLength = width * height * numberOfComponents;   
  
  
  
      NSMutableData * buffer= [NSMutableData dataWithLength :myDataLength];    
  
  
  
      [self checkForGLError]; 
  
  
  
      GLenum type = NUMBER_OF_COMPONENTS == 3 ? GL_RGB : GL_RGBA; //RGBA
  
      glReadPixels(0, 0, width, height, type, GL_UNSIGNED_BYTE, [buffer mutableBytes]);   //EXC_BAD_ACCESS here
  
  
  
      return buffer; 
  
  }

  It is working on iPhone 4 (4.3) and iPod Touch, but have problems on iPhone 3G(3.0) and iPad(4.3). Can you help me with this issue ?

  Also on iPhone 3G(3.0) and iPad(4.3) I have problems with Video - first 5-20 video frames have trash. Maybe issue with optimization ? Or architecture ?

  EDITED
  Stack :

  #0  0x33be3964 in void BlockNxN<64ul, 16ul, 1, BLOCK_CONVERTER_NULL_32>(unsigned long, int, int, unsigned long, int, int, unsigned int, unsigned int, unsigned int, unsigned int) ()
  
  #1  0x33be1c76 in glrBIFDetile ()
  
  #2  0x33b586b2 in sgxGetImage(SGXImageReadParams const*) ()
  
  #3  0x33b50d38 in gldReadPixels ()
  
  #4  0x31813e16 in glReadPixels_Exec ()
  
  #5  0x31e3c518 in glReadPixels ()

• Multi bitrate live HLS with FFmpeg on Windows

  16 mai 2014, par Nioreh

  I am trying to encode a live stream into Apple HLS for iPhone on windows. I was looking at different options and wowza can do it, but doesn’t support CDN distribution of HLS as far as I can see. Plus it costs a lot of money.

  What I did find was this site : http://www.espend.de/artikel/iphone-ipad-ipod-http-streaming-segmenter-and-m3u8-windows.html

  I can now set up a single bitrate stream easily, but my goal is an adapive multi-bitrate live stream. Is it possible ? For VOD content it can easily be accomplished with creating the different qualities then linking to them in a new m3u8, but how would this be done in live ?

  I can of course set up three quality live streams and link to them in an m3u8, but how will I get them GOP-aligned in this case ?

  My initial thought was to have one ffmpeg instance create all qualities and re-stream those outputs to new ffmpeg-instances that just remux and pipe to the segmenter. But I would need some way of streaming locally between instances. Can that be done ?

  If anyone has a nice solution to this, or can link to other software capable of live HLS on windows, I would appreciate any input.

  Have a great day !
  Regards
  Carl

• ffmpeg override the same file for every second of the video [on hold]

  5 février 2017, par Dorin Pleava

  I want to get one image for every 10 seconds from a livestream/video, but the image should have the same name, meaning I want to override it every cycle.

  This is my command :

  ffmpeg.exe -i http://iphone-streaming.ustream.tv/uhls/17074538/streams/live/iphone/playlist.m3u8 -bt 20M -s 480x300 -vf fps=1/10 -y photo.jpg

  This code works for one image but for the next I get this

  "Could not get frame filename number 2 from pattern ’photo.jpg’ (either set updatefirst or use a pattern like %03d within the filename pattern)
  av_interleaved_write_frame() : Invalid argument"

  If I replace photo.jpeg with photo%03d.jpg I get photo001.jpec, followed by photo002.jpeg, etc.