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• OpenGLES glReadPixels exc_bad_access

  29 novembre 2011, par Yanny

  I'm trying to create video from images using OpenGLES 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 ?

• Using ffmpeg to display a static image if an RTMP input source is missing

  19 mars 2016, par iameli

  Here is what I would like ffmpeg to output :

  • If I am streaming from my iPhone to my RTMP server, ffmpeg should output the live video from my iPhone.
  • If not, ffmpeg should output a blank red screen.

  Here’s what I have so far. It sort of works.

  ffmpeg \
  
    -f lavfi \
  
    -re \
  
    -i 'color=s=320x240:r=30:c=red' \
  
    -thread_queue_size 512 \
  
    -i 'rtmp://localhost/stream/iphone' \
  
    -c:v libx264 \
  
    -f flv \
  
    -filter_complex "\
  
      [1:v]scale=320:240[stream]; \
  
      [0:v][stream]overlay=0:0:eof_action=pass[output] \
  
    "\
  
    -map '[output]' \
  
    -tune zerolatency \
  
    'rtmp://localhost/stream/output'

  What happens : it boots up and starts streaming my iPhone’s output no problem. When I disconnect, it hangs for a long time, perhaps 20 seconds. Then it starts outputting red, okay. But then if I reconnect my phone, it doesn’t resume. It’s still red. Two questions :

  • Is there a way to configure the buffering so that it starts outputting red as soon as it stops getting data from the RTMP stream ?
  • Is there a way to have it auto-retry, so after the RTMP stream returns, it will switch back ?

  Full verbose output, if that’s helpful. I’m using the latest git version of ffmpeg as of 2016-03-18 on Ubuntu Wily. The RTMP server is nginx-rtmp.

• FFmpeg Concat Filter High Memory Usage

  14 février 2020, par user2248702

  I’m using FFmpeg to join many short clips into a single long video using the concat filter. FFmpeg seems to load all clips into memory at once and quickly runs out of RAM (For 100 clips it eats over 32GB). Is there a way to limit the memory used by the concat filter ?

  The command I would use for 3 inputs is as follows :

  ffmpeg -i 0.mp4 -i 1.mp4 -i 2.mp4 -filter_complex "[0:v][0:a][1:v][1:a][2:v][2:a]concat=n=3:v=1:a=1" out.mp4

  It seems to use around 200MB per additional input, which quickly uses all the memory in my system.