WebCam als schlanke alternative zum appVideoControl
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42
src/deviceDetect.js
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42
src/deviceDetect.js
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'use strict';
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const fs = require('fs');
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const path = require('path');
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// Returns ordered list of camera device paths.
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// Priority: DEV0/DEV1/... env vars → /dev/v4l/by-id/ → /dev/video*
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function detectDevices() {
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// Explicit env vars take priority
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const envDevices = [];
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for (let i = 0; i < 8; i++) {
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const dev = process.env[`DEV${i}`];
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if (dev) envDevices.push(dev);
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}
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if (envDevices.length > 0) return envDevices;
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// Stable device IDs (survive USB re-plug without renumbering)
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const byIdDir = '/dev/v4l/by-id';
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if (fs.existsSync(byIdDir)) {
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try {
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const found = fs.readdirSync(byIdDir)
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.filter(name => !name.endsWith('-index1')) // skip audio/metadata endpoints
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.map(name => fs.realpathSync(path.join(byIdDir, name)))
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.filter((v, i, arr) => arr.indexOf(v) === i) // deduplicate symlink targets
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.sort();
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if (found.length > 0) return found;
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} catch { /* fall through */ }
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}
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// Simple enumeration fallback (Linux)
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try {
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const found = fs.readdirSync('/dev')
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.filter(name => /^video\d+$/.test(name))
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.sort((a, b) => parseInt(a.slice(5)) - parseInt(b.slice(5)))
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.map(name => `/dev/${name}`);
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if (found.length > 0) return found;
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} catch { /* fall through */ }
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return ['/dev/video0', '/dev/video2'];
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}
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module.exports = { detectDevices };
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50
src/snapshotService.js
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50
src/snapshotService.js
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'use strict';
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const express = require('express');
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// Returns an Express router mounted at /api/snapshot
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// GET /api/snapshot → JSON listing of cameras
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// GET /api/snapshot/cam0 → latest JPEG from cam0
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// GET /api/snapshot/cam1 → latest JPEG from cam1
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function createSnapshotRouter(streams) {
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const router = express.Router();
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router.get('/', (_req, res) => {
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res.json({
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cameras: streams.map((s, i) => ({
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id: `cam${i}`,
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device: s.device,
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running: s.isRunning,
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clients: s.clientCount,
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hasFrame: s.latestFrame !== null,
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url: `/api/snapshot/cam${i}`,
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})),
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});
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});
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router.get('/:id', (req, res) => {
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const idx = parseInt(req.params.id.replace('cam', ''), 10);
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if (isNaN(idx) || !streams[idx]) {
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return res.status(404).json({ error: 'camera not found' });
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}
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const frame = streams[idx].latestFrame;
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if (!frame) {
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return res.status(503).json({ error: 'no frame available yet – stream may still be starting' });
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}
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res.set({
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'Content-Type': 'image/jpeg',
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'Content-Length': frame.length,
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'Cache-Control': 'no-store',
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'X-Camera-Id': `cam${idx}`,
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'X-Camera-Device': streams[idx].device,
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'X-Timestamp': new Date().toISOString(),
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});
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res.end(frame);
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});
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return router;
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}
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module.exports = { createSnapshotRouter };
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163
src/videoStream.js
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163
src/videoStream.js
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'use strict';
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const { spawn } = require('child_process');
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const { WebSocket } = require('ws');
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// JPEG frame boundaries
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const SOI = Buffer.from([0xff, 0xd8]);
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const EOI = Buffer.from([0xff, 0xd9]);
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// Max buffer before we assume stream corruption and discard
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const MAX_BUFFER = 2 * 1024 * 1024;
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// Drop frames to clients with a clogged send buffer (slow network/tab)
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const MAX_CLIENT_BUFFER = 512 * 1024;
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class VideoStream {
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constructor(device, options = {}) {
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this.device = device;
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this.name = options.name ?? 'cam';
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this.width = options.width ?? 640;
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this.height = options.height ?? 480;
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this.fps = options.fps ?? 30;
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this.quality = options.quality ?? 5; // FFmpeg MJPEG quality: 2=best … 31=worst
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this._clients = new Set();
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this._process = null;
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this._restartTimer = null;
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this._restartDelay = 1000;
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this._running = false;
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this._latestFrame = null;
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}
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get latestFrame() { return this._latestFrame; }
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get isRunning() { return this._running; }
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get clientCount() { return this._clients.size; }
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start() {
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if (this._running) return;
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this._running = true;
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this._spawn();
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}
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stop() {
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this._running = false;
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clearTimeout(this._restartTimer);
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if (this._process) {
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this._process.kill('SIGKILL');
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this._process = null;
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}
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}
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addClient(ws) {
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this._clients.add(ws);
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// Send latest frame immediately – client sees picture right away
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if (this._latestFrame) {
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ws.send(this._latestFrame, { binary: true });
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}
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}
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removeClient(ws) {
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this._clients.delete(ws);
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}
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// ---------------------------------------------------------------------------
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// FFmpeg pipeline
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// ---------------------------------------------------------------------------
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_buildArgs() {
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return [
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'-hide_banner', '-loglevel', 'warning',
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// Minimize input buffering for low latency
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'-fflags', 'nobuffer',
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'-flags', 'low_delay',
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'-probesize', '32',
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'-analyzeduration', '0',
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// Input: USB camera via Video4Linux2
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'-f', 'v4l2',
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'-input_format', 'mjpeg', // prefer hardware MJPEG (no re-decode if res matches)
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'-video_size', `${this.width}x${this.height}`,
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'-framerate', String(this.fps),
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'-i', this.device,
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// Output: scale to target size, encode as MJPEG to stdout
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// If camera delivers native MJPEG at target resolution, consider -vcodec copy
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'-vf', `scale=${this.width}:${this.height}`,
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'-f', 'mjpeg',
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'-q:v', String(this.quality),
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'pipe:1',
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];
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}
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_spawn() {
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console.log(`[${this.name}] starting ffmpeg on ${this.device}`);
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const startedAt = Date.now();
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const proc = spawn('ffmpeg', this._buildArgs(), {
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stdio: ['ignore', 'pipe', 'pipe'],
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});
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this._process = proc;
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let buf = Buffer.alloc(0);
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proc.stdout.on('data', (chunk) => {
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buf = Buffer.concat([buf, chunk]);
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let offset = 0;
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while (true) {
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const soi = buf.indexOf(SOI, offset);
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if (soi === -1) break;
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const eoi = buf.indexOf(EOI, soi + 2);
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if (eoi === -1) break;
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const frame = buf.slice(soi, eoi + 2);
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this._latestFrame = frame;
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this._broadcast(frame);
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this._restartDelay = 1000; // reset backoff on good frames
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offset = eoi + 2;
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}
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buf = offset > 0 ? buf.slice(offset) : buf;
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if (buf.length > MAX_BUFFER) {
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console.warn(`[${this.name}] buffer overflow, discarding`);
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buf = Buffer.alloc(0);
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}
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});
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proc.stderr.on('data', (chunk) => {
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const msg = chunk.toString().trimEnd();
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if (msg) console.error(`[${this.name}] ffmpeg: ${msg}`);
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});
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proc.on('close', (code) => {
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this._process = null;
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const uptime = Date.now() - startedAt;
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console.log(`[${this.name}] ffmpeg closed (code=${code}, uptime=${uptime}ms)`);
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if (!this._running) return;
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// Exponential backoff: 1s → 2s → 4s → 8s max
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console.log(`[${this.name}] restart in ${this._restartDelay}ms`);
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this._restartTimer = setTimeout(() => {
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this._restartDelay = Math.min(this._restartDelay * 2, 8000);
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this._spawn();
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}, this._restartDelay);
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});
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proc.on('error', (err) => {
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console.error(`[${this.name}] spawn error: ${err.message}`);
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});
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}
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_broadcast(frame) {
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for (const ws of this._clients) {
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if (ws.readyState !== WebSocket.OPEN) continue;
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// Drop frame for slow clients rather than queuing indefinitely
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if (ws.bufferedAmount > MAX_CLIENT_BUFFER) continue;
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ws.send(frame, { binary: true });
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}
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}
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}
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module.exports = { VideoStream };
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