gistfile1.js

var _mergeChunks = function(id, chunksArr, callback){
	var exec   = require('child_process').exec,
		tmpDir = config.getUploadPath(),
		fileHash = crypto.createHash('md5').update(id + moment().unix()).digest('hex'),
		txtFile =  'concat_' + fileHash + '_' + id + '.txt',
		videoOut = 'concat_' + fileHash + '_' + id + '.mp4',
		stream = fs.createWriteStream(tmpDir + '/' + txtFile),
		cmd;

	stream.once('open', function(fd) {
		_.each(chunksArr, function(chunk, chunkIndex){
			stream.write('file ' + '\'' + chunk.file.path + '\'' + "\n");
			if(chunkIndex == chunksArr.length -1) stream.end();
		});
	});

	cmd = 'ffmpeg -f concat'
		+ ' -i ' + tmpDir + '/' + txtFile
		+ ' -c copy ' + tmpDir + '/' + videoOut;

	console.log('FFMPEG', moment().unix(), cmd);

	exec(cmd, function(err, stdout, stderr){
		if(err) console.error('err: ' + err);
		console.info('stdout: ' + stdout);
		console.info('stderr: ' + stderr);

		if(null == err){
			_.each(chunksArr, function(chunkObj){
				console.log('Cleanup chunk ', chunkObj.file.path);
				fs.unlink(chunkObj.file.path);
			});
			console.log('Cleanup ffmpeg txt ', tmpDir + '/' + txtFile);
			fs.unlink(path.join(tmpDir, txtFile));

			callback(null, {outFile: path.join(tmpDir, videoOut), outFileName: videoOut});
		} else {
			callback(true, err);
		}
	});
}