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• ffmpeg how to calculate complete frame ['I' frame ] from [ 'P' frame ]. It is conceptually correct ?

  15 février 2014, par Whoami

  I am trying to get the knowledge of ffmpeg streaming video handling.

  what I understood :

  I get from the IPed Camaera, the frames like 'IPPPPPPPPPPPPPPPPIPPPPPPP'..

  Frame 'I' is a complete frame, where as frame 'P' depends on the previous either 'P' or 'I' frame which ever is the closes.

  I get the frame by using avcodec_decode_video2

  while (av_read_frame (context, &packet) >=0)
  
  {   
  
          //LOGD (" Received PACKET...DTS and PTS  %ld and %ld ", packet.pts, packet.dts);
  
  
  
          if(packet.stream_index == videoStreamIndex ) { 
  
                  avcodec_decode_video2 (pCodecCtx, pFrame, &finished, &packet);
  
                  if ( finished) {
  
                  // Here is my frame, getting the type by av_get_picture_type_char(pFrame->pict_type).
  
            }
  
   }

  Now, When i display just the frames that i have received, looks like whenever 'I' frame received, it displays properly, when received 'P' frames, the image goes for a toss.

  1) We need to manually do any calculation to convert 'P' Frame to 'I' Frame so that it can be rendered ?

  2) If not (1), what do i have to take care ?..Does DTS/PTS calcuation do the magic here ?

• Stream camera/video from python to client using ffmpeg

  31 janvier 2018, par Rahul

  So I’m making an application where I have connected my camera with python code through opencv.

  Now I can process each frame inside my python code but I want to stream this live feed to users.

  I found that FFmpeg can be used to achieve this but I’m wondering how.
  Also please do suggest any solution to achieve this with any other library.

  The only condition is that I should be able to stream from my python code may be via a subprocess.

  thanks in advance :)

• Extended client ownership of MediaCodec encoder output buffers for RTMP streaming

  13 février 2014, par dbro

  Background :

  I've connected Android's MediaCodec to FFmpeg for muxing a variety of formats not supported by MediaMuxer, including rtmp:// output via a .flv container. Such streaming muxers require longer, unpredictable ownership of MediaCodec's output buffers, as they may perform networking I/O on any packet processing step. For my video stream, I'm using MediaCodec configured for Surface input. To decouple muxing from encoding, I queue MediaCodec's ByteBuffer output buffers to my muxer via a Handler.

  All works splendidly if I mux the .flv output to file, rather than rtmp endpoint.

  Problem :

  When muxing to rtmp://... endpoint I notice my streaming application begins to block on calls to eglSwapBuffers(mEGLDisplay, mEncodingEGLSurface) at dequeueOutputBuffer() once I'm retaining even a few MediaCodec output buffers in my muxing queue as MediaCodec seems to be locked to only 4 output buffers.

  Any tricks to avoid copying all encoder output returned by MediaCodec#dequeueOutputBuffers and immediately calling releaseOutputBuffer(...) ?

  The full source of my project is available on Github. Specifically, see :

  • AndroidEncoder.java : Abstract Encoder class with shared behavior between Audio and Video encoders : mainly drainEncoder(). Writes data to a Muxer instance.
  • FFmpegMuxer.java : Implements Muxer
  • CameraEncoder.java. Sends camera frames to an AndroidEncoder subclass configured for Video encoding.

  Systrace

  

  Here's some systrace output streaming 720p @ 2Mbps video to Zencoder.

  Solved

  Copying then releasing the MediaCodec encoder output ByteBuffers as soon as they're available solves the issue without significantly affecting performance. I recycle the ByteBuffer copies in an ArrayDeque<bytebuffer></bytebuffer> for each muxer track, which limits the number of allocations.