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• Encoding FFMPEG to MPEG-DASH – or WebM with Keyframe Clusters – for MediaSource API

  6 août 2018, par Chris Nolet

  I’m currently sending a video stream to Chrome, to play via the MediaSource API.

  As I understand it, MediaSource only supports MP4 files encoded with MPEG-DASH, or WebM files that have clusters beginning with keyframes (otherwise it raises the error : Media segment did not begin with keyframe).

  Is there any way to encode in MPEG-DASH or keyframed WebM formats with FFMPEG in real-time ?

  Edit :

  I just tried it with ffmpeg ... -f webm -vcodec vp8 -g 1 so that every frame is a keyframe. Not the ideal solution. It does work with MediaStream now though. Any way to sync up the segments with the keyframes in WebM so not every frame needs to be a keyframe ?

  ---

  Reference Questions on WebM / MP4 and MediaSource :

  Media Source Api not working for a custom webm file (Chrome Version 23.0.1271.97 m)

  MediaSource API and mp4

• 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.