quickndirty: serving a /dev/video0 webcam via network

devvideo0.js

#!/usr/bin/env ndoe


var devicepath = '/dev/v4l/by-id/usb-Hewlett_Packard_HP_Webcam_HD_4310-video-index0';
var devicefps = 15;
var width = 1280;
var height = 720;
var bufsize = 512 * 1024 * 1024; // 512 MiB (perfect for a RPi)


var net = require('net');
var http = require('http');
var EventEmitter = require('events').EventEmitter;
var v4l2camera = require("v4l2camera");
var exec = require('child_process').exec;
var CronJob = require('cron').CronJob;

var stream = new EventEmitter();

var preframetime = Date.now();
var framerate = 0;
var framebuffer = new Buffer(0);
var jpegheader = new Buffer([0xFF, 0xD8, 0xFF, 0xDB]);
var framecounter = 0;

var log = function () {
	console.log.bind(this).apply(this, ['\r\33[2K' + new Date()].concat(Array.prototype.slice.call(arguments)));
};

var autoexposure = function (cb1, cb2) {
	log('Setting exposure to automatic');
	exec('v4l2-ctl -c exposure_auto=3 -d ' + devicepath, function (err, stdout, stderr) {
		if (typeof cb1 === 'function') {
			cb1();
		}
		setTimeout(function () {
			log('Setting exposure to fixed');
			exec('v4l2-ctl -c exposure_auto=1 -d ' + devicepath, function (err, stdout, stderr) {
				if (typeof cb2 === 'functioon') {
					cb2();
				}
			});
		}, 5000);
	});
};

/*new CronJob('0 0 * * * *', function () {
	autoexposure();
}, null, true, 'Etc/UTC');*/

exec('v4l2-ctl -v width=' + width + ',height=' + height + ',pixelformat=MJPG -d ' + devicepath, function (err, stdout, stderr) {
exec('v4l2-ctl -p ' + devicefps + ' -d ' + devicepath, function (err, stdout, stderr) {
exec('v4l2-ctl -c focus_auto=0 -d ' + devicepath, function (err, stdout, stderr) {
exec('v4l2-ctl -c focus_absolute=0 -d ' + devicepath, function (err, stdout, stderr) {
	var firstframe = true;
	var cam = new v4l2camera.Camera(devicepath);
	if (cam.configGet().formatName !== "MJPG") {
		log('NOTICE: MJPG camera required');
		process.exit(1);
	}
	cam.start();
	autoexposure();
	var getimage = function () {
		cam.capture(function (success) {
			if (stream.listeners('frame').length) {
				process.nextTick(getimage);
			} else {
				setTimeout(getimage, 1000);
			}
			if (!success) {
				return;
			}
			var frame = Buffer(cam.frameRaw());
			if (!frame.slice(0, 4).equals(jpegheader)) {
				return;
			}
			if (firstframe) {
				//exec('v4l2-ctl -c exposure_auto=1 -d ' + devicepath);
				firstframe = false;
			}
			var curframetime = Date.now();
			stream.emit('frame', curframetime, frame);
			framecounter++;
			framerate = (framerate * 99 + 1000 / (curframetime - preframetime)) / 100;
			preframetime = curframetime;
			framebuffer = frame;
		});
	};
	getimage();
});
});
});
});

setInterval(function () {
	process.stdout.write([
		'\r\33[2K' + (new Date()),
		'framebuffer.length=' + framebuffer.length,
		'frame.rate=' + Math.round(framerate * 100) / 100,
		'listeners.length=' + stream.listeners('frame').length,
		'framecounter=' + framecounter
	].join(' '));
}, 500);

var tcpserver = net.createServer(function (socket) {
	var addr = socket.remoteAddress;
	log(addr, 'connect', 'tcp');
	var stats = {total:0,sent:0,dropped:0};
	var forward = function (frametime, frame) {
		stats.total++;
		if (socket._writableState.length < bufsize / stream.listeners('frame').length) {
			stats.sent++;
			socket.write(frame);
		} else {
			stats.dropped++;
		}
	};
	stream.on('frame', forward);
	socket.on('error', new Function());
	socket.on('close', function () {
		log(addr, 'disconnect', 'tcp', 'total=' + stats.total, 'sent=' + stats.sent, 'dropped=' + stats.dropped, '(' + Math.round(stats.sent / stats.total * 10000) / 100 + '%/' + Math.round(stats.dropped / stats.total * 10000) / 100 + '%)');
		stream.removeListener('frame', forward);
	});
});

var httpserver = http.createServer(function (req, res) {
	var addr = req.socket.remoteAddress;
	log(addr, 'connect', 'http');
	var stats = {total:0,sent:0,dropped:0};
	var forward = function (frametime, frame) {
		stats.total++;
		if (res._writableState.length < bufsize / stream.listeners('frame').length) {
			stats.sent++;
			socket.write(frame);
		} else {
			stats.dropped++;
		}
	};
	stream.on('frame', forward);
	req.on('error', new Function());
	res.on('error', new Function());
	req.on('close', function () {
		log(addr, 'disconnect', 'http', 'total=' + stats.total, 'sent=' + stats.sent, 'dropped=' + stats.dropped, '(' + Math.round(stats.sent / stats.total * 10000) / 100 + '%/' + Math.round(stats.dropped / stats.total * 10000) / 100 + '%)');
	});	
});

var picserver = net.createServer(function (socket) {
	socket.on('error', new Function());
	socket.end(framebuffer);
});

tcpserver.listen(9000);
httpserver.listen(8000);
picserver.listen(7000);