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• spawn ffmpeg in nodejs and pipe to express's response

  18 décembre 2017, par ViGi

  i am spawning ffmpeg and pipe it’s output (the video stream i want) to express’s response object like this :

  app.get('/stream', (req, res) => {
  
      let _url = req.query.url;
  
  
  
      if(_url){   
  
  
  
          res.writeHead(200, {
  
              'Access-Control-Allow-Origin': '*',
  
              'Connection': 'Keep-Alive',
  
              'Content-Type': 'video/mp4'
  
          });
  
  
  
          // transcode rtsp input from ip-cam to mp4 file format (video: h.264 | audio: aac)
  
          let ffmpeg = child_process.spawn("ffmpeg",[
  
              "-probesize","2147483647",
  
              "-analyzeduration","2147483647",
  
              "-i", _url,
  
              "-vcodec","copy",
  
              "-f", "mp4",            
  
              "-movflags","frag_keyframe+empty_moov+faststart",
  
              "-frag_duration","3600",
  
              "pipe:1"              
  
          ]);         
  
  
  
  
  
          // redirect transcoded ip-cam stream to http response
  
          ffmpeg.stdout.pipe(res);
  
  
  
          // error logging
  
          ffmpeg.stderr.setEncoding('utf8');      
  
          ffmpeg.stderr.on('data', (data) => {
  
              console.log(data);
  
          });
  
      }
  
      else{
  
          res.end();
  
      }

  so far it’s working like a charm.
  however somewhere in there seems to be a cap. i can get only 3 streams running at the same time. when a 4th spawn occurs the 4th thread will block one of the cpu cores :

  

  and naturally the 4th stream does not reach the browser..
  has somebody any idea of what am i missing ?

  EDIT : it’s not tied to the fact that i am running the nodejs project on the raspberry pi. it also behaves the same way on my windows 10 machine

• Encoding 4K 60Hz lossless from a capture card

  13 décembre 2017, par Alex Pizzi

  Windows 10 64-bit
  Ryzen 7
  GTX 1080
  32GB RAM

  Hi all,

  I’m trying to encode 4K 30/60Hz video in a lossless format from a 4K capture card and everything I’ve tried gives me a similar error as in the linked image, [real-time buffer too full or near too full frame dropped]

  [Not mine]
  https://cloud.githubusercontent.com/assets/4932401/22171307/ef5c9864-df58-11e6-8821-4b74ce3f32d0.png

  This is the command I’ve tried most recently :

  ffmpeg.exe -f dshow -video_size 3840x2160 -framerate 30 -pixel_format bgr24 -rtbufsize INT_MAX -i video="MZ0380 PCI, Analog 01 Capture" -vf fps=30 out%d.BMP

  With the images dumped to a 10G RAM disk or 850 EVO. I’m doing this to skip the encoding step.

  I get the same error when encoding with h265 lossless and NVENC h265 lossless.

  I need the video to be lossless as it will be used to test hardware h265 encoders.

  Video source is a 4K Blu-ray.

  Any help would be greatly appreciated. Thank you.

  -Alex P

• Trouble understanding XHR streams and express

  17 janvier 2017, par Jon

  I’m having some trouble understanding how I can trigger an XHR response from an express server res.write.

  I’m creating a request on the client with the following code :

   var xhr = new XMLHttpRequest();
  
  
  
   xhr.open(opts.method || 'get', url);
  
  
  
   for (var k in opts.headers||{}) {
  
     xhr.setRequestHeader(k, opts.headers[k]);
  
   }
  
  
  
   xhr.onload = e => res(e.target.responseText);
  
   xhr.onerror = rej;
  
  
  
   if (xhr.upload && progressCb) {
  
     xhr.upload.onprogress = progressCb;
  
   }
  
  
  
   xhr.send(opts.body);

  On the node server, I’m doing multiple res.write() in response to this request.

  For example, I’m creating a video using ffmpeg() and throughout the creation process, I’ll res.write() a JSON.stringified status update.

  The client will receive the last .write(), but the xhr.upload.onprogress callback is not triggered, so I don’t think I understand how to use it correctly. I’m guessing that the xhr.upload.onprogress is meant solely for callbacks related to uploading data to the server, not for triggering a response to multiple writes

  Is there a way for an XHR request to fire a callback every time it receives a res.write() from express ? If not, what’s a better way of achieving this goal ?