Use FFmpeg’s machine-readable -progress output as a heartbeat, and have a supervisor detect when complete progress updates stop arriving. Treat that as evidence about FFmpeg’s activity—not proof that YouTube is receiving a healthy stream. Check YouTube’s Live Control Room separately for ingest status and inspect playback for viewer-facing audio and video quality.
What a watchdog can—and cannot—tell you
A YouTube streaming setup has several distinct signals. No single one establishes that the stream is healthy from encoder to viewer:
- FFmpeg progress updates: indicate that FFmpeg is reporting encoding progress. A stale feed may mean the process is hung, blocked, or otherwise not producing updates.
- Process exit status and stderr: indicate whether FFmpeg terminated and may give diagnostic context for an error.
- YouTube Live Control Room: reports the status and health of the stream YouTube is receiving, including specific error messages. See YouTube’s live stream metrics guidance.
- Playback inspection: helps catch viewer-facing problems such as missing audio, frozen video, or poor quality that a running encoder does not rule out.
Pair the watchdog with YouTube’s dashboard and, where possible, a separate playback check. YouTube advises monitoring stream health and reviewing messages during an event, as well as monitoring continuous audio and video quality in its encoder settings guidance and live streaming tips.
How FFmpeg’s progress output works
FFmpeg’s -progress option emits machine-readable key=value lines. Each complete update ends with a progress key whose value is continue or end. Use -stats_period to choose the reporting interval; the FFmpeg documentation gives a default of 0.5 seconds. A one-second interval is a reasonable illustrative choice for a watchdog, not a required or universally optimal setting. See the FFmpeg CLI documentation.
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Count an update only when its terminating progress line arrives. If you refresh the heartbeat for every line, a partial record could make a stalled encoder look active. Keep progress output separate from human-readable diagnostics: send it to stdout with -progress pipe:1, and capture stderr separately.
Set up the YouTube destination safely
- Get the ingest URL and stream key. In YouTube Live Control Room, create or select the live stream and copy its server URL and stream key. YouTube’s RTMPS instructions explain that RTMPS is RTMP over TLS/SSL and describe finding the URL and key in the Control Room.
- Prefer RTMPS where available. YouTube documents RTMP and RTMPS for encoder streaming and recommends RTMPS. Keep the key out of public scripts, source control, command transcripts, and logs. Restrict access to any environment file or secret store that contains it.
- Choose encoding settings for the actual output. YouTube documents H.264, H.265/HEVC, and AV1, frame rates up to 60 fps, and a recommended two-second keyframe interval that should not exceed four seconds. Bitrate recommendations vary by codec, resolution, and frame rate; consult the current table in YouTube’s encoder settings guidance for the combination you will send.
- Confirm the stream in Live Control Room. A successful FFmpeg launch does not establish that YouTube has accepted the stream or that its audio and video are suitable for viewers.
A watchdog pattern for POSIX systems
The following Python 3 example supervises FFmpeg on POSIX-like systems. It reads progress records without blocking the timeout check, writes stderr to a separate log, notices process exits, terminates the child process group on shutdown or stale progress, and limits retries with exponential backoff. It is a starting point, not a tested deployment for every host or FFmpeg build; validate it with your input, service manager, and signal-handling requirements before an event.
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Save as watch_ffmpeg.py. Set INPUT to a valid FFmpeg input and provide the YouTube RTMPS URL and key through protected environment variables. The script deliberately does not print the output URL or key.
#!/usr/bin/env python3
import os
import selectors
import signal
import subprocess
import sys
import time
INPUT = os.environ.get("INPUT", "input.mp4")
RTMPS_URL = os.environ["YOUTUBE_RTMPS_URL"]
STREAM_KEY = os.environ["YOUTUBE_STREAM_KEY"]
OUTPUT = f"{RTMPS_URL.rstrip('/')}/{STREAM_KEY}"
STALE_SECONDS = float(os.environ.get("STALE_SECONDS", "30"))
MAX_RESTARTS = int(os.environ.get("MAX_RESTARTS", "5"))
BACKOFF_SECONDS = float(os.environ.get("BACKOFF_SECONDS", "2"))
LOG_PATH = os.environ.get("FFMPEG_LOG", "ffmpeg-stderr.log")
STOP = False
def request_stop(signum, frame):
global STOP
STOP = True
signal.signal(signal.SIGINT, request_stop)
signal.signal(signal.SIGTERM, request_stop)
def run_once():
cmd = [
"ffmpeg", "-nostdin", "-re", "-i", INPUT,
"-c:v", "libx264", "-c:a", "aac",
"-f", "flv",
"-stats_period", "1", "-progress", "pipe:1",
OUTPUT,
]
with open(LOG_PATH, "ab", buffering=0) as errlog:
proc = subprocess.Popen(
cmd, stdin=subprocess.DEVNULL, stdout=subprocess.PIPE,
stderr=errlog, start_new_session=True,
)
sel = selectors.DefaultSelector()
sel.register(proc.stdout, selectors.EVENT_READ)
last_update = time.monotonic()
record = {}
reason = "process exited"
try:
while not STOP:
if proc.poll() is not None:
return proc.returncode, "process exited"
events = sel.select(timeout=1)
for key, _ in events:
line = key.fileobj.readline()
if not line:
continue
text = line.decode("utf-8", errors="replace").strip()
if "=" not in text:
continue
name, value = text.split("=", 1)
record[name] = value
if name == "progress":
last_update = time.monotonic()
ended = value == "end"
record.clear()
if ended:
return proc.wait(), "progress=end"
if time.monotonic() - last_update > STALE_SECONDS:
reason = f"no complete progress update for {STALE_SECONDS:g} seconds"
return None, reason
return None, "shutdown requested"
finally:
sel.close()
if proc.poll() is None:
try:
os.killpg(proc.pid, signal.SIGTERM)
proc.wait(timeout=10)
except subprocess.TimeoutExpired:
os.killpg(proc.pid, signal.SIGKILL)
proc.wait()
proc.stdout.close()
restarts = 0
while not STOP:
code, reason = run_once()
print(f"{time.strftime('%Y-%m-%dT%H:%M:%SZ', time.gmtime())} {reason}; exit={code}", file=sys.stderr, flush=True)
if STOP or reason == "progress=end":
break
if restarts >= MAX_RESTARTS:
print("restart limit reached; stopping", file=sys.stderr, flush=True)
sys.exit(code if code is not None else 1)
delay = BACKOFF_SECONDS * (2 ** restarts)
restarts += 1
time.sleep(delay)
Example environment variables (store them in a file readable only by the service account, or inject them using your secret manager):
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INPUT=/srv/video/program.mp4
YOUTUBE_RTMPS_URL=rtmps://YOUR_INGEST_HOST/YOUR_PATH
YOUTUBE_STREAM_KEY=YOUR_PRIVATE_STREAM_KEY
STALE_SECONDS=30
MAX_RESTARTS=5
BACKOFF_SECONDS=2
FFMPEG_LOG=/var/log/ffmpeg-stderr.logReplace the ingest host and path with the exact URL shown in Live Control Room. The example uses -re for a file input so it is read at its native rate; for a live capture or another real-time source, adapt the input options rather than copying that flag blindly. The sample encoding choices are illustrative; use YouTube’s current settings table for your chosen codec, resolution, and frame rate.
Choose and validate the stale timeout
STALE_SECONDS is an operator-selected threshold, not an FFmpeg or YouTube standard. Give ordinary network interruptions, irregular sources, and host load enough room that routine pauses do not trigger restarts. A short threshold can cause unnecessary disconnects; an overly long one delays recovery. Test with the real source and host, then adjust. The script counts restarts per run and stops at the configured limit rather than retrying forever.
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Read the outcomes correctly
- Progress is stale while the PID remains alive: the watchdog stops the FFmpeg process group and retries within its limit. Inspect the timestamped supervisor output and stderr log to diagnose the cause.
- FFmpeg exits: the supervisor records the exit status and retries within its limit. An exit is distinct from a live process with a stale progress feed.
- FFmpeg reports
progress=end: the example treats this as normal completion and does not restart. For a finite file that is intended to loop, configure the FFmpeg input or playlist for looping rather than treating normal completion as a hang. - The process reports progress but YouTube shows an error: investigate the ingest status and message in Live Control Room; the local heartbeat cannot diagnose YouTube’s receiving state.
The sample appends FFmpeg stderr to a log but does not rotate it; set up log rotation and access controls appropriate to your host. If you manage FFmpeg with systemd, a container orchestrator, or another supervisor, avoid stacking independent unlimited restart loops. Choose one layer to own retries, and keep the other’s policy bounded and observable.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Test recovery before relying on it
Test the primary and backup path before an event, and confirm that viewers actually see the intended result. YouTube’s live streaming tips recommend testing a backup encoder by stopping the primary encoder or disconnecting its Ethernet, then checking that the player rolls over to the backup. Also test how your watchdog responds to a stopped FFmpeg process, a deliberately stalled source, and a rejected or unavailable ingest destination. Confirm that a recovery does not expose the stream key in logs.
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