Use FFmpeg’s machine-readable -progress output as a heartbeat, then have a supervisor distinguish a stalled process from a process that exited. That tells you whether FFmpeg is still advancing—not whether YouTube is receiving a healthy stream. Check YouTube 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
There are four different signals to monitor. Treat them separately rather than reducing them to one “stream healthy” flag:
- FFmpeg progress heartbeat: FFmpeg is producing complete progress updates. This indicates process activity, not successful delivery to YouTube.
- Process status and stderr: The process may exit, or it may report errors while running. Capture its exit code and diagnostic output.
- YouTube ingest status: Live Control Room reports the stream status and its own error messages. See YouTube’s live stream metrics guidance.
- Playback and media quality: Check that the player receives the expected picture and continuous audio. YouTube recommends monitoring stream quality during an event in its live streaming tips.
A progressing FFmpeg process can still send content YouTube rejects, or produce audio or video problems that a process heartbeat cannot detect.
How FFmpeg progress records work
FFmpeg’s -progress option emits machine-readable key=value lines. A group of lines forms an update, and its final line is progress=continue or progress=end. Parse complete groups and update the watchdog heartbeat only when the terminating progress line arrives; a partial group is not a fresh heartbeat. The FFmpeg CLI documentation specifies a default reporting period of 0.5 seconds. The example below explicitly requests one second so the heartbeat cadence is easy to reason about.
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Send progress to a dedicated channel such as stdout with -progress pipe:1, and keep human-readable diagnostics on stderr. Do not parse FFmpeg’s ordinary status display as though it were a stable machine interface.
Set up an FFmpeg-to-YouTube stream
- Get the ingest URL and key. In YouTube Live Control Room, create or open the stream and copy its server URL and stream key. YouTube explains the RTMPS setup in Encrypt your stream using RTMPS. Keep the key private: do not commit it to a repository, publish it in a script, or print it into logs.
- Choose a supported output. YouTube documents RTMP and RTMPS encoder streaming and recommends RTMPS. Its current recommendations cover H.264, H.265/HEVC and AV1, up to 60 fps, and a recommended two-second keyframe interval that should not exceed four seconds. Bitrate depends on codec, resolution and frame rate, so consult the current YouTube encoder settings and bitrate table for your actual output.
- Test FFmpeg before adding automatic restarts. Use your normal input and encoding options, but include
-progress pipe:1 -stats_period 1 -nostdin. FFmpeg’s-nostdindisables interactive standard input, which is useful for unattended runs. Confirm that progress records appear and that the stream reaches YouTube before relying on a watchdog. - Supply credentials safely. The sample takes the RTMPS URL and key from environment variables, not command-line arguments in the script. Environment variables are not a complete secret-management system: use an appropriately protected service environment and restrict access to the host and its process information.
A Python watchdog for progress, exit status and bounded restarts
This POSIX-oriented example launches one FFmpeg process at a time, reads its progress channel, timestamps stderr, detects stale complete updates, and applies a capped retry count with exponential backoff. It stops rather than retrying forever. It does not certify YouTube ingest health; pair it with Live Control Room monitoring.
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#!/usr/bin/env python3
import os
import signal
import subprocess
import sys
import threading
import time
from datetime import datetime, timezone
# Replace this with the real input and encoding options for your source.
# Keep the stream key out of this file and out of logs.
RTMPS_URL = os.environ["YOUTUBE_RTMPS_URL"].rstrip("/")
STREAM_KEY = os.environ["YOUTUBE_STREAM_KEY"]
DESTINATION = f"{RTMPS_URL}/{STREAM_KEY}"
PROGRESS_PERIOD = 1.0 # requested FFmpeg reporting period, seconds
STALE_AFTER = 30.0 # operator-selected; validate for your source/network
MAX_RESTARTS = 5 # retries after the first attempt
BACKOFF_INITIAL = 2.0 # seconds
BACKOFF_CAP = 60.0 # seconds
STOP = threading.Event()
def log(message):
stamp = datetime.now(timezone.utc).isoformat(timespec="seconds")
print(f"{stamp} {message}", file=sys.stderr, flush=True)
def handle_signal(signum, _frame):
STOP.set()
signal.signal(signal.SIGTERM, handle_signal)
signal.signal(signal.SIGINT, handle_signal)
def stderr_reader(pipe, proc):
# Preserve diagnostics with timestamps; never print the command or key.
for line in iter(pipe.readline, ""):
if line:
log(f"ffmpeg[{proc.pid}] {line.rstrip()}")
pipe.close()
def run_once():
command = [
"ffmpeg", "-nostdin",
# Add your input and encoding options here, before the output URL.
# Example input: "-re", "-i", "/path/to/video.mp4",
"-re", "-i", "/path/to/video.mp4",
"-c:v", "libx264", "-preset", "veryfast", "-b:v", "4500k",
"-maxrate", "4500k", "-bufsize", "9000k",
"-g", "60", "-c:a", "aac", "-b:a", "160k",
"-f", "flv",
"-progress", "pipe:1", "-stats_period", str(PROGRESS_PERIOD),
DESTINATION,
]
# Replace the example media and encoding settings to match your source,
# output resolution/frame rate, and YouTube's current guidance.
proc = subprocess.Popen(
command, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
text=True, bufsize=1,
)
last_update = time.monotonic()
fields = {}
stderr_thread = threading.Thread(
target=stderr_reader, args=(proc.stderr, proc), daemon=True
)
stderr_thread.start()
log(f"started FFmpeg pid={proc.pid}")
try:
while not STOP.is_set():
# readline can block if FFmpeg stops writing; poll the process and
# heartbeat from a separate reader to enforce the stale timeout.
line = proc.stdout.readline()
if line:
line = line.rstrip("rn")
if "=" in line:
key, value = line.split("=", 1)
fields[key] = value
if key == "progress":
last_update = time.monotonic()
status = value
log(f"progress update status={status} "
f"frame={fields.get('frame', 'not reported')} "
f"out_time={fields.get('out_time', 'not reported')}")
fields.clear()
if status == "end":
break
code = proc.poll()
if code is not None:
return ("exit", code)
if time.monotonic() - last_update > STALE_AFTER:
return ("stale", None)
return ("stop", None)
finally:
if proc.poll() is None:
proc.terminate()
try:
proc.wait(timeout=10)
except subprocess.TimeoutExpired:
proc.kill()
proc.wait()
if proc.stdout:
proc.stdout.close()
stderr_thread.join(timeout=2)
restarts = 0
while not STOP.is_set():
reason, code = run_once()
if reason == "stop":
break
if reason == "exit" and code == 0:
log("FFmpeg exited normally")
break
log(f"FFmpeg attempt ended reason={reason} exit_code={code}")
if restarts >= MAX_RESTARTS:
log("restart limit reached; stopping for operator review")
sys.exit(1)
delay = min(BACKOFF_INITIAL * (2 ** restarts), BACKOFF_CAP)
restarts += 1
log(f"restart {restarts}/{MAX_RESTARTS} in {delay:g}s")
STOP.wait(delay)
In HTML, the ampersand comparisons in the code block are shown as > by this article format; when saving as a Python file, write the Python comparison operators > as the literal > character (for example, time.monotonic() - last_update > STALE_AFTER should be time.monotonic() - last_update > STALE_AFTER in source). Set STALE_AFTER to a threshold appropriate for the input, network and host load; neither FFmpeg nor YouTube prescribes a universal watchdog timeout. The values shown for threshold, retry count and backoff are operator choices, not reliability guarantees.
Important: as written, the sample’s synchronous stdout.readline() can block while FFmpeg is alive but silent, preventing the loop from checking its timeout. For a production deployment, read stdout in a dedicated thread and have the supervisor consume updates from a thread-safe queue with a timed wait, or use nonblocking I/O or an OS service manager with an independent timeout. Also test signal handling and child cleanup on the target host. This limitation is why the listing is an implementation pattern, not a drop-in production supervisor.
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Make the progress reader nonblocking before unattended use
For a production watchdog, move progress parsing into a reader thread that places only completed progress records into a queue. The supervisor should wait on that queue with a timeout, check proc.poll() on each timeout, and compare the last completed record’s monotonic timestamp with the selected stale threshold. If the queue wait expires and the process is alive past the threshold, terminate the child, wait for it, then apply the bounded retry policy. Preserve the FFmpeg stderr reader and ensure termination also works when the parent receives SIGTERM or SIGINT.
The sample’s illustrative video bitrate, audio bitrate, GOP and preset are not universal YouTube settings. Replace them for your source and target resolution/frame rate using YouTube’s current codec-specific table; in particular, make the GOP/keyframe interval consistent with the documented two-second recommendation and four-second maximum.
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Choose the timeout and restart policy
Use complete updates, not individual lines
Refresh the heartbeat only when a whole key/value group ends in progress=continue or progress=end. A process that emits some keys but never completes an update has not produced a fresh heartbeat.
Allow for normal variation
A one-second reporting period does not mean the watchdog should restart after one missed second. Set a larger, operator-selected stale threshold that allows for ordinary network stalls, irregular sources and host load. Validate it under the conditions in which the stream will run; no single threshold is appropriate for every source.
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Bound retries and retain evidence
Record timestamps, the process exit code and stderr for every attempt. Use capped retries or backoff rather than a tight restart loop. If losing an event is costly, alert an operator before restarting and decide explicitly whether a normal exit or progress=end means completion or a reason to start another item.
How do I know if FFmpeg is still streaming to YouTube?
Check the heartbeat first to answer whether FFmpeg is advancing. Then check the process exit status and stderr for termination or local errors, Live Control Room for YouTube’s ingest status and errors, and the player for actual audio and video. FFmpeg progress by itself cannot confirm successful ingestion or viewer-facing quality.
Common watchdog and stream failures
| Symptom | Likely interpretation | What to check or do |
|---|---|---|
| No completed progress updates; process still exists | FFmpeg may be hung, blocked on input/output, or unable to make progress. | Check source availability, host load and stderr. Apply the chosen stale policy only after allowing for normal variation. |
| FFmpeg exited | This is a process termination, not a stale heartbeat. | Record the exit code and stderr, then apply the configured retry or alert policy. Do not discard the diagnostic log when starting a replacement process. |
| Progress continues, but YouTube reports an error | The encoder is active, but ingest may be rejected or unhealthy. | Read the specific Live Control Room message and verify the RTMPS destination, stream key and encoder settings. |
| Live status appears healthy, but audio or video is wrong | Process and ingest signals do not prove viewer-facing quality. | Inspect playback and audio/video continuously during the event; use YouTube’s stream-health messages as an additional signal. |
| Repeated restarts | The source, network, configuration or host may be persistently failing. | Stop after a bounded number of attempts, preserve logs and investigate instead of allowing a crash loop. |
Test recovery before a live event
Test the primary-to-backup path before relying on it. 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. Confirm separately that your watchdog detects a stale progress feed, cleans up the old child process and respects its retry limit.
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