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• Faster Real Time A.R Drone Video Streaming

  5 septembre 2017, par mike

  I’ve attempted ffplay tcp://192.168.1.1:5555 to video stream from the AR Drone 2.0 ; however, the delay is way too high.

  My second attempt was with the following :

  var arDrone = require('ar-drone');
  
  var http    = require('http');
  
  
  
  console.log('Connecting png stream ...');
  
  
  
  var pngStream = arDrone.createClient().getPngStream();
  
  
  
  var lastPng;
  
  pngStream
  
    .on('error', console.log)
  
    .on('data', function(pngBuffer) {
  
      lastPng = pngBuffer;
  
    });
  
  
  
  var server = http.createServer(function(req, res) {
  
    if (!lastPng) {
  
      res.writeHead(503);
  
      res.end('Did not receive any png data yet.');
  
      return;
  
    }
  
  
  
    res.writeHead(200, {'Content-Type': 'image/png'});
  
    res.end(lastPng);
  
  });
  
  
  
  server.listen(8080, function() {
  
    console.log('Serving latest png on port 8080 ...');
  
  });

  This only streamed images. I had to refresh browser every second.

  My third option was using this option :

  var arDrone=require('ar-drone')
  
  var client= arDrone.createclient();
  
  require('ar-drone-png-stream')(client,{port:8000})

  It streamed a lot of images in a short amount of time. The delay is still significant and I’m looking for a video.

  Are there other approaches that will significantly lower the delay of the video stream ?

• How to give real timestamp information to encoded frames inside mpeg1 container

  24 août 2021, par jackey balwani

  I referred following link for my implementation. https://ffmpeg.org/doxygen/trunk/muxing_8c_source.html
I am converting raw data rgb to yuv420 format through scaling and conversion apis available in FFMPEG and then passing the frames to MPEG1 encoder.
I observe that the encoded video plays too fast. Below is the code of encoding the frame and then writing it to output file.

  


    static int write_frame(AVFormatContext *fmt_ctx, AVCodecContext *c,
                    AVStream *st, AVFrame *frame)
  {
    int ret;

    // send the frame to the encoder
    ret = avcodec_send_frame(c, frame);
    if (ret < 0) {
     fprintf(stderr, "Error sending a frame to the encoder: %s\n",
             av_err2str(ret));
     exit(1);
   }

   while (ret >= 0) {
     AVPacket pkt = { 0 };

     ret = avcodec_receive_packet(c, &pkt);
     if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
         break;
     else if (ret < 0) {
         fprintf(stderr, "Error encoding a frame: %s\n", av_err2str(ret));
         exit(1);
     }

     /* rescale output packet timestamp values from codec to stream timebase */
     av_packet_rescale_ts(&pkt, c->time_base, st->time_base);
     pkt.stream_index = st->index;

     /* Write the compressed frame to the media file. */
     log_packet(fmt_ctx, &pkt);
     ret = av_interleaved_write_frame(fmt_ctx, &pkt);
     av_packet_unref(&pkt);
     if (ret < 0) {
         fprintf(stderr, "Error while writing output packet: %s\n", av_err2str(ret));
         exit(1);
     }
 }

 return ret == AVERROR_EOF ? 1 : 0;
}


  


  resulting mpeg video's playback time is very quick, hence video gets played so fast.

  


  so to match output video duration with input video coming from source, I am trying to pass following realtime information to Avframe structure before calling avcodec_send_frame() -

  


  


  1. realtime PTS value (current time + duration got through av_gettime() in microseconds) to AvFrame structure before calling avcodec_send_frame().

     


  


  2. populating pkt_duration with time difference between frames (current_PTS - previous_PTS)

     


  


  3. Removed this call av_packet_rescale_ts(&pkt, c->time_base, st->time_base) ; which is used after avcodec_receive_packet.

     


  


  


  below highlighted code are the changes done for real time info-

  


  **static int64_t m_currVideopts = 0;
static int64_t m_prevVideopts = 0;**

static int write_frame(AVFormatContext *fmt_ctx, AVCodecContext *c, AVStream *st, AVFrame *frame)
{
  **int64_t pts = av_gettime();  // returns current time in micro seconds
  int64_t duration = 90000/STREAM_FRAME_RATE;    /*duration for first frame taken default as 
   3600 as we dont have reference frame to compare diff */
  pts = av_rescale_q(pts, (AVRational){1, 1000000}, st->time_base);    //pAvStream->time_base - stream time base (1:90000)
  if((m_prevVideopts > 0LL) && (pts > m_prevVideopts))
  {
    duration = pts - m_prevVideopts;
  }
  else if (pts < m_prevVideopts)
  {
    pts = m_prevVideopts + duration;
  }
  m_prevVideopts = pts;
  /* Going with the approach of pts value is equal to pts value for every  packet */
  frame->pts = m_currVideopts;    /*AV_NOPTS_VALUE; */
  m_currVideopts += duration;
  //pFfmpegVidCtx->next_pts = m_currVideopts;
  frame->pkt_duration = duration;**

 // send the frame to the encoder
 ret = avcodec_send_frame(c, frame);
 if (ret < 0) {
     fprintf(stderr, "Error sending a frame to the encoder: %s\n",
             av_err2str(ret));
     exit(1);
 }
 ....
 // receive the packet avcodec_receive_packet()
 ...
 
 // removed or commented av_packet_rescale_ts
 **/* av_packet_rescale_ts(&pkt, c->time_base, st->time_base) */**
 ret = av_interleaved_write_frame(fmt_ctx, &pkt);


  


  }

  


  with the above changes, video is not playing proper.
There are couple of issues with respect to total duration (some time it is not proper on player) and also some frames are getting dropped or lost while playing in vlc or media player.

  


  

  


  I am unable to find the cause of these frames loss while playing. Is it the correct way of passing real time pts information to the encoder or any mistake in above code.
Any suggestion would help me proceed further,
thanks.

  


• Revision 18d323606d : Fix test to call clear system state in convolve_test. Assembly tests should cle

  12 décembre 2014, par Jim Bankoski

  Changed Paths :
   Modify /test/convolve_test.cc

  
  
  Fix test to call clear system state in convolve_test.

  Assembly tests should clear system state, as we have no
  expectation of proper system state in between test runs..

  Change-Id : I0f591996c1f17ef2a5a8572a6b445f757223a144