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• Convert ffmpeg yuv420p AVFrame to CMSampleBufferRef (kcvPixelFormatType_420YpCbCr8BiPlanarFullRange)

  21 juillet 2014, par user3272750

  I have a foscam ip camera and have access to the rtsp stream. I used DFURTSPPlayer to view the stream on my iOS device which works fine. I use a webrtc provider that lets me inject frames as CMSampleBufferRef in addition to directly reading from any of the on board cameras. I wish to use this to broadcast the IP camera stream over a secure webrtc session.

  The main loop in the DFURTSPPLayer checks if a frame is available and then converts into UIimage and sets it to an imageview.

  -(void)displayNextFrame:(NSTimer *)timer
  
  {
  
      NSTimeInterval startTime = [NSDate timeIntervalSinceReferenceDate];
  
      if (![video stepFrame]) {
  
          [timer invalidate];
  
          [playButton setEnabled:YES];
  
          [video closeAudio];
  
          return;
  
      }
  
      imageView.image = video.currentImage;
  
      float frameTime = 1.0/([NSDate timeIntervalSinceReferenceDate]-startTime);
  
      if (lastFrameTime<0) {
  
          lastFrameTime = frameTime;
  
      } else {
  
          lastFrameTime = LERP(frameTime, lastFrameTime, 0.8);
  
      }
  
      [label setText:[NSString stringWithFormat:@"%.0f",lastFrameTime]];
  
  }

  I’m trying to do something similar, but instead of (or in addition to) setting the UIImage I wish to also inject the frames into my webrtc service. This is an example where they use an avcapturesession. I believe I could do something similar to the runloop here and inject the frame (provided I can convert the yuv420p AVFrame into a CMSampleBufferRef :

  - (void) captureOutput:(AVCaptureOutput*) captureOutput
  
   didOutputSampleBuffer:(CMSampleBufferRef) sampleBuffer
  
          fromConnection:(AVCaptureConnection*) connection
  
  {
  
      self.videoFrame.frameBuffer = sampleBuffer;
  
  
  
      // IMPORTANT: injectFrame expects a 420YpCbCr8BiPlanarFullRange and frame
  
      //            gets timestamped inside the service.
  
      NSLog(@"videoframe buffer %@",self.videoFrame.frameBuffer);
  
      [self.service injectFrame:self.videoFrame];
  
  }

  Hence my question. Most of the questiosn on stack overflow involve going in the other direction (typically broadcasting on board camera input via rtsp). I’m a n00b as far as avfoundation/corevideo is concerned. I’m prepared to put in the groundwork if someone can suggest a path. Thanks in advance !

  Edit : After reading some more on this, it seems that most important step is a conversion from 420p to 420f.

• Alternative to ffmpeg for dynamically creating video thumbnails [closed]

  4 juillet 2021, par Daniel Rusev

  The server hosting my website doesn't have ffmpeg and I am not allowed to install any additional extensions. Is there any other way I can make video thumbnails dynamically ? Perhaps some kind of web service, where I pass the video file and as a result I get a picture file. I'm using php, by the way.

  


• Do ffmpeg and ffprobe share the same code for metadata extraction ?

  3 décembre 2013, par user931392

  I want to make a simple transcoding service and I want to use ffprobe (because of the -print_format option) to get the metdata of a file (duration, width x height (if required), bit rate, etc) and ffmpeg for the transcoding itself.

  My question is :
  Is it safe to use the metadata from the ffprobe output to generate a command line for ffmpeg ?