使用 Content-Range 在 Node.js 中流式传输音频

Question

I'm using a streaming server in Node.js to stream MP3 files. While the whole file streaming it is ok, I cannot use the Content-Range header to stream the file seeking to a start position and util a end position.

I calculate the start and end bytes from seconds using ffprobe like

ffprobe -i /audio/12380187.mp3 -show_frames -show_entries frame=pkt_pos -of default=noprint_wrappers=1:nokey=1 -hide_banner -loglevel panic -read_intervals 20%+#1

That will give me the exact bytes from 10 seconds in this case to the first next packet.

This becomes in Node.js as simple as

  const args = [
      '-hide_banner',
      '-loglevel', loglevel,
      '-show_frames',//Display information about each frame
      '-show_entries', 'frame=pkt_pos',// Display only information about byte position
      '-of', 'default=noprint_wrappers=1:nokey=1',//Don't want to print the key and the section header and footer
      '-read_intervals', seconds+'%+#1', //Read only 1 packet after seeking to position 01:23
      '-print_format', 'json',
      '-v', 'quiet',
      '-i', fpath
    ];
    const opts = {
      cwd: self._options.tempDir
    };
    const cb = (error, stdout) => {
      if (error)
        return reject(error);
      try {
        const outputObj = JSON.parse(stdout);
        return resolve(outputObj);
      } catch (ex) {
        return reject(ex);
      }
    };
    cp.execFile('ffprobe', args, opts, cb)
      .on('error', reject);
  });

Now that I have start and end bytes, my media server will get the ranges in this way from a custom value passed to it like bytes=120515-240260

var getRange = function (req, total) {
  var range = [0, total, 0];
  var rinfo = req.headers ? req.headers.range : null;

  if (rinfo) {
    var rloc = rinfo.indexOf('bytes=');
    if (rloc >= 0) {
      var ranges = rinfo.substr(rloc + 6).split('-');
      try {
        range[0] = parseInt(ranges[0]);
        if (ranges[1] && ranges[1].length) {
          range[1] = parseInt(ranges[1]);
          range[1] = range[1] < 16 ? 16 : range[1];
        }
      } catch (e) {}
    }

    if (range[1] == total)
     range[1]--;

    range[2] = total;
  }

  return range;
};

At this point I will get this range [ 120515, 240260, 4724126 ] , where I have like [startBytes,endBytes,totalDurationInBytes]

I therfore can create a file read stream passing that range:

var file = fs.createReadStream(path, {start: range[0], end: range[1]});

and then compose the response header using

  var header = {
    'Content-Length': range[1],
    'Content-Type': type,
    'Access-Control-Allow-Origin': req.headers.origin || "*",
    'Access-Control-Allow-Methods': 'POST, GET, OPTIONS',
    'Access-Control-Allow-Headers': 'POST, GET, OPTIONS'
  };

  if (range[2]) {
    header['Expires'] = 0;
    header['Pragma'] = 'no-cache';
    header['Cache-Control']= 'no-cache, no-store, must-revalidate';
    header['Accept-Ranges'] = 'bytes';
    header['Content-Range'] = 'bytes ' + range[0] + '-' + range[1] + '/' + total;
    header['Content-Length'] = range[2];
    //HTTP/1.1 206 Partial Content
    res.writeHead(206, header);
  } else {
    res.writeHead(200, header);
  }

so to obtain

{
 "Content-Length": 4724126,
  "Content-Type": "audio/mpeg",
  "Access-Control-Allow-Origin": "*",
  "Access-Control-Allow-Methods": "POST, GET, OPTIONS",
  "Access-Control-Allow-Headers": "POST, GET, OPTIONS",
  "Accept-Ranges": "bytes",
  "Content-Range": "bytes 120515-240260/4724126"
}

before doing the pipe of the read stream to the output

file.pipe(res);

The problem is that the browser I don't get any audio in the HTML5 <audio> tag, while it was streaming the contents when not using any Content-Range header. Here you can see the dump of the ReadStream object from the node api that shows how the range was ok

  start: 120515,
  end: 240260,
  autoClose: true,
  pos: 120515

So what is happening on the browser side that prevents to load the file?

[UPDATE]

It turns out that it works Safari but not in Google's Chrome ! I can then assume that the Content-Range it correctly devised, but Chrome has some flawness with it. Now the specification is by rfc2616 and I'm following strictly that one for the byte-range-resp-spec so I pass

  "Accept-Ranges": "bytes",
  "Content-Range": "bytes 120515-240260/4724126"

and this should work on Chrome too according to the RFC specs. This it should work as-it-is as specified by Mozilla docs as well here

Answer 1

I'm using expressjs framework and I've made it like this:

// Readable Streams Storage Class
class FileReadStreams {
  constructor() {
    this._streams = {};
  }
  
  make(file, options = null) {
    return options ?
      fs.createReadStream(file, options)
      : fs.createReadStream(file);
  }
  
  get(file) {
    return this._streams[file] || this.set(file);
  }
  
  set(file) {
    return this._streams[file] = this.make(file);
  }
}
const readStreams = new FileReadStreams();

// Getting file stats and caching it to avoid disk i/o
function getFileStat(file, callback) {
  let cacheKey = ['File', 'stat', file].join(':');
  
  cache.get(cacheKey, function(err, stat) {
    if(stat) {
      return callback(null, stat);
    }
    
    fs.stat(file, function(err, stat) {
      if(err) {
        return callback(err);
      }
      
      cache.set(cacheKey, stat);
      callback(null, stat);
    });
  });
}

// Streaming whole file
function streamFile(file, req, res) {
  getFileStat(file, function(err, stat) {
    if(err) {
      console.error(err);
      return res.status(404).end();
    }
    
    let bufferSize = 1024 * 1024;
    res.writeHead(200, {
      'Cache-Control': 'no-cache, no-store, must-revalidate',
      'Pragma': 'no-cache',
      'Expires': 0,
      'Content-Type': 'audio/mpeg',
      'Content-Length': stat.size
    });
    readStreams.make(file, {bufferSize}).pipe(res);
  });
}

// Streaming chunk
function streamFileChunked(file, req, res) {
  getFileStat(file, function(err, stat) {
    if(err) {
      console.error(err);
      return res.status(404).end();
    }
    
    let chunkSize = 1024 * 1024;
    if(stat.size > chunkSize * 2) {
      chunkSize = Math.ceil(stat.size * 0.25);
    }
    let range = (req.headers.range) ? req.headers.range.replace(/bytes=/, "").split("-") : [];
    
    range[0] = range[0] ? parseInt(range[0], 10) : 0;
    range[1] = range[1] ? parseInt(range[1], 10) : range[0] + chunkSize;
    if(range[1] > stat.size - 1) {
      range[1] = stat.size - 1;
    }
    range = {start: range[0], end: range[1]};
    
    let stream = readStreams.make(file, range);
    res.writeHead(206, {
      'Cache-Control': 'no-cache, no-store, must-revalidate',
      'Pragma': 'no-cache',
      'Expires': 0,
      'Content-Type': 'audio/mpeg',
      'Accept-Ranges': 'bytes',
      'Content-Range': 'bytes ' + range.start + '-' + range.end + '/' + stat.size,
      'Content-Length': range.end - range.start + 1,
    });
    stream.pipe(res);
  });
}

router.get('/:file/stream', (req, res) => {

  const file = path.join('path/to/mp3/', req.params.file+'.mp3');
    
  if(/firefox/i.test(req.headers['user-agent'])) {
    return streamFile(file, req, res);
  }
  streamFileChunked(file, req, res);
});

Full sources of site here

Try to fix to Your code:

this will enforce browser to act with resource as chunked.

var header = {
    'Content-Length': range[1],
    'Content-Type': type,
    'Access-Control-Allow-Origin': req.headers.origin || "*",
    'Access-Control-Allow-Methods': 'POST, GET, OPTIONS',
    'Access-Control-Allow-Headers': 'POST, GET, OPTIONS',
    'Cache-Control': 'no-cache, no-store, must-revalidate',
    'Pragma': 'no-cache',
    'Expires': 0
  };

  if(/firefox/i.test(req.headers['user-agent'])) {  
    res.writeHead(200, header);
  }
  else {
    header['Accept-Ranges'] = 'bytes';
    header['Content-Range'] = 'bytes ' + range[0] + '-' + range[1] + '/' + total;
    header['Content-Length'] = range[2];
    res.writeHead(206, header);
  }