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• Unhandled stream error in pipe : write EPIPE in Node.js

  13 juillet 2020, par Michael Romanenko

  The idea is to serve screenshots of RTSP video stream with Express.js server. There is a continuously running spawned openRTSP process in flowing mode (it's stdout is consumed by another ffmpeg process) :

  



  function spawnProcesses (camera) {
  var openRTSP = spawn('openRTSP', ['-c', '-v', '-t', camera.rtsp_url]),
      encoder = spawn('ffmpeg', ['-i', 'pipe:', '-an', '-vcodec', 'libvpx', '-r', 10, '-f', 'webm', 'pipe:1']);

  openRTSP.stdout.pipe(encoder.stdin);

  openRTSP.on('close', function (code) {
    if (code !== 0) {
      console.log('Encoder process exited with code ' + code);
    }
  });

  encoder.on('close', function (code) {
    if (code !== 0) {
      console.log('Encoder process exited with code ' + code);
    }
  });

  return { rtsp: openRTSP, encoder: encoder };
}

...

camera.proc = spawnProcesses(camera);


  



  There is an Express server with single route :

  



  app.get('/cameras/:id.jpg', function(req, res){
  var camera = _.find(cameras, {id: parseInt(req.params.id, 10)});
  if (camera) {
    res.set({'Content-Type': 'image/jpeg'});
    var ffmpeg = spawn('ffmpeg', ['-i', 'pipe:', '-an', '-vframes', '1', '-s', '800x600', '-f', 'image2', 'pipe:1']);
    camera.proc.rtsp.stdout.pipe(ffmpeg.stdin);
    ffmpeg.stdout.pipe(res);
  } else {
    res.status(404).send('Not found');
  }
});

app.listen(3333);


  



  When i request http://localhost:3333/cameras/1.jpg i get desired image, but from time to time app breaks with error :

  



  stream.js:94
  throw er; // Unhandled stream error in pipe.
        ^
Error: write EPIPE
    at errnoException (net.js:901:11)
    at Object.afterWrite (net.js:718:19)


  



  Strange thing is that sometimes it successfully streams image to res stream and closes child process without any error, but, sometimes, streams image and falls down.

  



  I tried to create on('error', ...) event handlers on every possible stream, tried to change pipe(...) calls to on('data',...) constructions, but could not succeed.

  



  My environment : node v0.10.22, OSX Mavericks 10.9.

  



  UPDATE :

  



  I wrapped spawn('ffmpeg',... block with try-catch :

  



  app.get('/cameras/:id.jpg', function(req, res){
....
    try {
      var ffmpeg = spawn('ffmpeg', ['-i', 'pipe:', '-an', '-vframes', '1', '-s', '800x600', '-f', 'image2', 'pipe:1']);
      camera.proc.rtsp.stdout.pipe(ffmpeg.stdin);
      ffmpeg.stdout.pipe(res);
    } catch (e) {
      console.log("Gotcha!", e);
    }
....
});


  



  ... and this error disappeared, but log is silent, it doesn't catch any errors. What's wrong ?

  


• Unhandled stream error in pipe : write EPIPE in Node.js

  28 novembre 2013, par Michael Romanenko

  The idea is to serve screenshots of RTSP video stream with Express.js server. There is a continuously running spawned openRTSP process in flowing mode (it's stdout is consumed by another ffmpeg process) :

  function spawnProcesses (camera) {
  
    var openRTSP = spawn('openRTSP', ['-c', '-v', '-t', camera.rtsp_url]),
  
        encoder = spawn('ffmpeg', ['-i', 'pipe:', '-an', '-vcodec', 'libvpx', '-r', 10, '-f', 'webm', 'pipe:1']);
  
  
  
    openRTSP.stdout.pipe(encoder.stdin);
  
  
  
    openRTSP.on('close', function (code) {
  
      if (code !== 0) {
  
        console.log('Encoder process exited with code ' + code);
  
      }
  
    });
  
  
  
    encoder.on('close', function (code) {
  
      if (code !== 0) {
  
        console.log('Encoder process exited with code ' + code);
  
      }
  
    });
  
  
  
    return { rtsp: openRTSP, encoder: encoder };
  
  }
  
  
  
  ...
  
  
  
  camera.proc = spawnProcesses(camera);

  There is an Express server with single route :

  app.get('/cameras/:id.jpg', function(req, res){
  
    var camera = _.find(cameras, {id: parseInt(req.params.id, 10)});
  
    if (camera) {
  
      res.set({'Content-Type': 'image/jpeg'});
  
      var ffmpeg = spawn('ffmpeg', ['-i', 'pipe:', '-an', '-vframes', '1', '-s', '800x600', '-f', 'image2', 'pipe:1']);
  
      camera.proc.rtsp.stdout.pipe(ffmpeg.stdin);
  
      ffmpeg.stdout.pipe(res);
  
    } else {
  
      res.status(404).send('Not found');
  
    }
  
  });
  
  
  
  app.listen(3333);

  When i request http://localhost:3333/cameras/1.jpg i get desired image, but from time to time app breaks with error :

  stream.js:94
  
    throw er; // Unhandled stream error in pipe.
  
          ^
  
  Error: write EPIPE
  
      at errnoException (net.js:901:11)
  
      at Object.afterWrite (net.js:718:19)

  Strange thing is that sometimes it successfully streams image to res stream and closes child process without any error, but, sometimes, streams image and falls down.

  I tried to create on('error', ...) event handlers on every possible stream, tried to change pipe(...) calls to on('data',...) constructions, but could not succeed.

  My environment : node v0.10.22, OSX Mavericks 10.9.

  UPDATE :

  I wrapped spawn('ffmpeg',... block with try-catch :

  app.get('/cameras/:id.jpg', function(req, res){
  
  ....
  
      try {
  
        var ffmpeg = spawn('ffmpeg', ['-i', 'pipe:', '-an', '-vframes', '1', '-s', '800x600', '-f', 'image2', 'pipe:1']);
  
        camera.proc.rtsp.stdout.pipe(ffmpeg.stdin);
  
        ffmpeg.stdout.pipe(res);
  
      } catch (e) {
  
        console.log("Gotcha!", e);
  
      }
  
  ....
  
  });

  ... and this error disappeared, but log is silent, it doesn't catch any errors. What's wrong ?

• Trolls in trouble

  6 juin 2013, par Mans — Law and liberty

  Life as a patent troll is hopefully set to get more difficult. In a memo describing patent trolls as a “drain on the American economy,” the White House this week outlined a number of steps it is taking to stem this evil tide. Chiming in, the Chief Judge of the Court of Appeals for the Federal Circuit (where patent cases are heard) in a New York Times op-ed laments the toll patent trolling is taking on the industry, and urges judges to use powers already at their disposal to make the practice less attractive. However, while certainly a step in the right direction, these measures all fail to address the more fundamental properties of the patent system allowing trolls to exist in the first place.

  System and method for patent trolling

  Most patent trolling operations comprise the same basic elements :

  1. One or more patents with broad claims.
  2. The patents of (1) acquired by an otherwise non-practising entity (troll).
  3. The entity of (2) filing numerous lawsuits alleging infringement of the patents of (1).
  4. The lawsuits of (3) targeting end users or retailers.
  5. The lawsuits of (3) listing as plaintiffs difficult to trace shell companies.

  The recent legislative actions all take aim at the latter entries in this list. In so doing, they will no doubt cripple the trolls, but the trolls will remain alive, ready to resume their wicked ways once a new loophole is found in the system.

  To kill a patent troll

  As Judge Rader and his co-authors point out in the New York Times, “the problem stems largely from the fact that, [...] trolls have an important strategic advantage over their adversaries : they don’t make anything.” This is the heart of the troll, and this is where the blow should be struck. Our weapon shall be the mightiest judicial sword of all, the Constitution.

  The United States Constitution contains (in Article I, Section 8) the foundation for the patent system (emphasis mine) :

  The Congress shall have Power [...] To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries.

  Patent trolls are typically not inventors. They are merely hoarders of other people’s discarded inventions, and that allowing others to reap the benefits of an inventor’s work would somehow promote progress should be a tough argument. Indeed, it is the dissociation between investment and reward which has allowed the patent trolls to rise and prosper.

  In light of the above, the solution to the troll menace is actually strikingly simple : make patents non-transferable.

  Having the inventor retain the rights to his or her inventions (works for hire still being recognised), would render the establishment of non-practising entities, which most trolls are, virtually impossible. The original purpose of patents, to protect the investment of inventors, would remain unaffected, if not strengthened, by such a change.

  Links

  • Taking on Patent Trolls to Protect American Innovation
  • Fact Sheet : White House Task Force on High-Tech Patent Issues
  • Make Patent Trolls Pay in Court
  • Constitution of the United States