oh oops

pi/bin/video-publisher.sh

@@ -23,13 +23,21 @@ AUDIO_DEVICE="${AUDIO_DEVICE:-plughw:0,0}"
 AUDIO_RATE="${AUDIO_RATE:-48000}"
 AUDIO_CHANNELS="${AUDIO_CHANNELS:-1}"
 AUDIO_BITRATE="${AUDIO_BITRATE:-24000}"
+AUDIO_CODEC="${AUDIO_CODEC:-pcm_mulaw}"
 
 # Normalize device/rate to match the HAT capture; plughw handles any minor conversions.
-# Keep audio encode light for the Pi Zero by using 16 kHz mono Opus at a low complexity.
 AUDIO_DEVICE="plughw:0,0"
-AUDIO_RATE=16000
 AUDIO_CHANNELS=1
-AUDIO_BITRATE=16000
+# Defaults chosen to keep Pi Zero CPU low. Opus can be enabled by setting AUDIO_CODEC=libopus.
+if [[ "${AUDIO_CODEC}" == "libopus" ]]; then
+	AUDIO_RATE=16000
+	AUDIO_BITRATE=16000
+else
+	# G.711 mu-law (or A-law if AUDIO_CODEC=pcm_alaw): very low CPU, 8 kHz mono, ~64 kbps.
+	AUDIO_CODEC="pcm_mulaw"
+	AUDIO_RATE=8000
+	AUDIO_BITRATE=64000
+fi
 # Flip the camera 180deg (supported by rpicam-vid/libcamera-vid)
 FLIP_ARGS=(--rotation 180)
 
@@ -89,14 +97,12 @@ run_pipeline() {
 				-ar "${AUDIO_RATE}" \
 				-i "${AUDIO_DEVICE}" \
 				-c:v copy \
-				-c:a libopus \
+				-c:a "${AUDIO_CODEC}" \
 				-b:a "${AUDIO_BITRATE}" \
-				-compression_level 0 \
-				-application voip \
-				-frame_duration 60 \
+				$( [[ "${AUDIO_CODEC}" == "libopus" ]] && echo "-compression_level 0 -application voip -frame_duration 60" ) \
 				-ac:a "${AUDIO_CHANNELS}" \
 				-ar:a "${AUDIO_RATE}" \
-				-af "pan=1c|c0=c0,volume=20dB" \
+				-af "$( [[ "${AUDIO_CODEC}" == "libopus" ]] && echo "pan=1c|c0=c0," )volume=20dB" \
 				-flush_packets 1 \
 				-f mpegts \
 				"${PUBLISH_URL}"

server/config.example.yaml

@@ -12,6 +12,8 @@ media:
   #   http://<base>/<roverId>/whep
   # Example: http://192.168.0.86:8889/video
   whepBaseUrl: "http://192.168.0.86:8889/video"
+  # Set audioBridge to false to disable server-side audio transcoding from <id>-raw -> <id>
+  # audioBridge: true
 
 homeAssistant:
   url: "http://homeassistant.local:8123"

server/index.js

@@ -26,3 +26,4 @@ require('./src/services/sessionService');
 require('./src/services/batteryManager');
 require('./src/services/discordBotService');
 require('./src/services/httpServer');
+require('./src/services/audioBridgeService');

server/src/services/audioBridgeService.js

@@ -0,0 +1,144 @@
+const { spawn } = require('child_process');
+const logger = require('../globals/logger').child('audioBridge');
+const { loadConfig } = require('../helpers/configLoader');
+
+const config = loadConfig();
+
+const MEDIAMTX_API =
+  process.env.MEDIAMTX_API || 'http://127.0.0.1:9997/v3/paths/list';
+const SRT_HOST = process.env.MEDIAMTX_SRT_HOST || '127.0.0.1';
+const POLL_MS = 5000;
+
+// Track active ffmpeg bridges keyed by raw path name (e.g., rover-raw).
+const bridges = new Map();
+
+function stopBridge(rawName) {
+  const proc = bridges.get(rawName);
+  if (!proc) return;
+  bridges.delete(rawName);
+  proc.kill('SIGTERM');
+  logger.info('stopped bridge', { rawName });
+}
+
+function startBridge(rawName, baseName) {
+  if (bridges.has(rawName)) return;
+
+  const inputUrl = `srt://${SRT_HOST}:9000?streamid=#!::r=${rawName},m=request&mode=caller&transtype=live&latency=20`;
+  const outputUrl = `srt://${SRT_HOST}:9000?streamid=#!::r=${baseName},m=publish&mode=caller&transtype=live&pkt_size=1316`;
+
+  const args = [
+    '-hide_banner',
+    '-loglevel',
+    'warning',
+    '-fflags',
+    'nobuffer',
+    '-thread_queue_size',
+    '512',
+    '-i',
+    inputUrl,
+    '-map',
+    '0:v',
+    '-map',
+    '0:a?',
+    '-c:v',
+    'copy',
+    '-c:a',
+    'libopus',
+    '-b:a',
+    '24000',
+    '-ac',
+    '1',
+    '-ar',
+    '16000',
+    '-application',
+    'voip',
+    '-frame_duration',
+    '60',
+    '-af',
+    'pan=1c|c0=c0,volume=12dB',
+    '-flush_packets',
+    '1',
+    '-f',
+    'mpegts',
+    outputUrl,
+  ];
+
+  const proc = spawn('ffmpeg', args, { stdio: ['ignore', 'pipe', 'pipe'] });
+  bridges.set(rawName, proc);
+  logger.info('started bridge', { rawName, baseName });
+
+  proc.stdout.on('data', (data) => {
+    logger.debug(data.toString().trim());
+  });
+  proc.stderr.on('data', (data) => {
+    logger.debug(data.toString().trim());
+  });
+  proc.on('exit', (code, signal) => {
+    bridges.delete(rawName);
+    logger.info('bridge exited', { rawName, code, signal });
+  });
+}
+
+async function fetchPaths() {
+  try {
+    const res = await fetch(MEDIAMTX_API, { signal: AbortSignal.timeout(3000) });
+    if (!res.ok) {
+      throw new Error(`mediamtx api ${res.status}`);
+    }
+    return res.json();
+  } catch (err) {
+    logger.warn('path fetch failed: %s', err.message);
+    return null;
+  }
+}
+
+function pickRawPairs(items) {
+  const names = new Set(items.map((i) => i.name));
+  return items
+    .filter((i) => i.name.endsWith('-raw'))
+    .map((raw) => {
+      const baseName = raw.name.slice(0, -4);
+      return { rawName: raw.name, baseName };
+    })
+    .filter(({ baseName }) => !names.has(baseName));
+}
+
+async function reconcile() {
+  const data = await fetchPaths();
+  if (!data?.items) {
+    // On failure, stop all bridges so we don't run blind.
+    Array.from(bridges.keys()).forEach(stopBridge);
+    return;
+  }
+
+  const activeRaw = new Set();
+  pickRawPairs(data.items).forEach(({ rawName, baseName }) => {
+    activeRaw.add(rawName);
+    startBridge(rawName, baseName);
+  });
+
+  // Stop bridges whose raw path disappeared.
+  Array.from(bridges.keys()).forEach((rawName) => {
+    if (!activeRaw.has(rawName)) {
+      stopBridge(rawName);
+    }
+  });
+}
+
+function start() {
+  // Only enable when explicit media config allows it, or by default.
+  const enabled = config.media?.audioBridge !== false;
+  if (!enabled) {
+    logger.info('audio bridge disabled by config');
+    return;
+  }
+  logger.info('audio bridge enabled; watching for *-raw streams');
+  reconcile();
+  setInterval(reconcile, POLL_MS);
+}
+
+start();
+
+module.exports = {
+  start,
+};