HTML5 Audio (mp3) and Video (webm) live transcoding streams

gistfile1.md

The following two functions will stream just about any audio or video file to any browsers supporting mp3 and/or webm. Due to the unknown number of bytes, a custom html5 audio/video player will have to be written (my next step) to allow seeking.

For w/e reason node.js didn't want to spawn a child process with a unix pipe in it. This could be so that they can keep support for windows computers. As such I've created the following bash script:

#!/bin/bash
START_TIME=${2:-0}
VARIABLE_BIT_RATE=${3:-4}
ABSOLUTE_PATH=$1

if [ -z $ABSOLUTE_PATH ];
then
	echo "{ \"ERROR\" : \"Not given an absolute path to the media file\" }" 
else
	ffmpeg -ss $START_TIME -i $ABSOLUTE_PATH -f wav - | lame --vbr-new -V $VARIABLE_BIT_RATE - -
fi

The relavent node.js code to transcode and stream audio/video on the fly

exports.sendVideoFile = function(params, res) {
    res.writeHead({
        'X-Content-Duration' : params.source.duration, //in seconds
        'Content-Duration'   : params.source.duration, //in seconds
        'Content-Type'       : 'video/webm'
    });
    var ffmpeg = childProcess.spawn('ffmpeg',  [
        '-i', params.location,      //location of our video file (use absolute, else you'll have a bad time)
        '-ss', '0',                 //starting time offset
        '-c:v', 'libvpx',           //video using vpx (webm) codec
        '-b:v', '1M',               //1Mb/s bitrate for the video
        '-cpu-used', '2',           //total # of cpus used
        '-threads', '4',            //number of threads shared between all cpu-used
        '-deadline', 'realtime',    //speeds up transcode time (necessary unless you want frames dropped)
        '-strict', '-2',            //ffmpeg complains about using vorbis, and wanted this param
        '-c:a', 'libvorbis',        //audio using the vorbis (ogg) codec
        "-f", "webm",               //filetype for the pipe
        'pipe:1'                    //send output to stdout
    ]); 
    ffmpeg.stdout.pipe(res);
    res.on('close', function() {
        ffmpeg.kill();
    });
}
  
  
  
exports.sendAudioFile = function(params, res) {
    res.writeHead({
      'X-Content-Duration' : params.source.duration,
      'Content-Duration'   : params.source.duration,
      'Content-Type'       : 'audio/mp3'
    });
    var audioConv = childProcess.spawn(__dirname + '/audioConv.sh',[
        params.location,  //first parameter is the file's location relative to the bash script
        0,                //second parameter specifies a start time offset
        3,                //third parameter specifies which variable encoding to use 0-9, with 0 being the best 9 the worst
    ]);
    audioConv.stdout.pipe(res);
    res.on('close', function() {
      audioConv.kill();
    });
    audioConv.stderr.on('data', function(d) {
       console.log(d.toString());
    });
};