To loop a 4K video into a YouTube Live stream, run FFmpeg with -stream_loop -1 and -re before the input, then send the encoded output to the RTMPS address and stream key shown in YouTube Live Control Room. The command below is a starting point for a 4K, 30 fps SDR H.264 file; adjust its bitrate and keyframe interval to match your frame rate and codec.
Before you start
- Install an FFmpeg build that includes the encoder you plan to use. The example uses
libx264; not every build includes it. - Have a 4K source file and a stable connection with enough sustained upload capacity for your chosen bitrate, plus headroom. Run a speed test rather than assuming a connection’s advertised maximum will be sustained.
- In YouTube Live Control Room, create or schedule a stream and copy its server URL and stream key. Treat the key like a password: do not publish it, and reset it if it is exposed. See YouTube’s encoder setup instructions.
- Check that you have the right to stream the video and its audio. A prerecorded loop is still a public YouTube live stream; looping material does not grant permission to use it or remove the need to follow YouTube’s copyright rules.
Choose the output settings
YouTube’s current encoder guidance recommends RTMPS, CBR, and a two-second keyframe interval, with no interval longer than four seconds. Its 4K bitrate recommendations depend on codec and frame rate:
| Output | YouTube-recommended video bitrate |
|---|---|
| 2160p at 30 fps, AV1 or H.265 | 30 Mbps |
| 2160p at 30 fps, H.264 | 42 Mbps |
| 2160p at 60 fps, AV1 or H.265 | 35 Mbps |
| 2160p at 60 fps, H.264 | 50 Mbps |
These are YouTube ingest recommendations, not a promise that viewers will receive 4K. YouTube processes incoming streams into playback versions, and the resolution available to a viewer depends on platform processing, device, and connection. YouTube recommends H.265 for HDR and says AV1 is not supported for HDR; check its encoder settings before choosing HDR or a codec.
For 4K, YouTube does not offer its low-latency optimization; expect normal latency. In the example below, -g 60 is a two-second GOP only at 30 fps. At another frame rate, set the GOP to approximately two seconds of frames—for example, 120 at 60 fps.
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Run FFmpeg and loop the file
For a 4K 30 fps SDR source, H.264 output, and stereo AAC audio, use this pattern. Replace input.mp4 with your file path and the destination with the RTMPS server URL and key from YouTube Live Control Room. Keep the actual key private.
ffmpeg
-stream_loop -1 -re -i "input.mp4"
-c:v libx264 -preset veryfast
-b:v 42M -maxrate 42M -bufsize 84M
-g 60
-c:a aac -b:a 128k
-f flv "rtmps://SERVER/APP/STREAM_KEY"-stream_loop -1 repeats the input indefinitely, and -re reads it at its native rate rather than sending it as fast as FFmpeg can process it. Both options belong before the -i they apply to. The video bitrate and max rate are set to the 42 Mbps YouTube recommendation for 4K 30 fps H.264; the 84 Mbps buffer is twice that rate. The command uses FLV output with an RTMPS destination, a pattern supported by FFmpeg’s command documentation. YouTube recommends RTMPS for ingest.
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This example does not force frame rate, scale, pixel format, or color metadata. Inspect your source first and add conversions only if needed; unnecessary frame-rate or color changes can alter motion or appearance. Use a GOP appropriate to your actual output frame rate. The example is illustrative, not a tested universal command.
When stream copying may work
If the source codecs, container stream, bitrate, and keyframe spacing are suitable for YouTube ingest, -c copy can avoid re-encoding and reduce CPU use. It also means you cannot change the encoded bitrate or keyframe spacing. Compatibility depends on the actual source streams, so verify ingest and stream health rather than assuming any 4K file can be copied directly. FFmpeg documents copy as stream copying without re-encoding at ffmpeg.org/ffmpeg.html.
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Start and monitor the YouTube stream
- Open YouTube Live Control Room and use the stream URL and key for the stream you created or scheduled. Paste these into the FFmpeg destination in the format shown above; do not share the key.
- Start the FFmpeg command and watch the encoder preview in Live Control Room. For a scheduled stream, wait for the preview, then select Go live.
- Check stream health, video, and audio. YouTube advises testing with audio and movement similar to what the actual stream will contain; a representative test can expose bitrate, encoding, and sound issues before the intended broadcast.
- To stop the loop, interrupt the FFmpeg process. If the YouTube event is scheduled or manually started, also end it in Live Control Room as appropriate.
See YouTube’s live stream settings guidance for stream management and recovery of a compromised key.
Troubleshoot common failures
YouTube does not receive a signal
- Confirm that the server URL and key are the ones shown for the current stream, and that the key has not been reset. Check for missing quotes, spaces, or shell characters in the destination.
- Verify FFmpeg’s output for connection or encoder errors. Confirm that your FFmpeg build includes
libx264if you use the example. - Use RTMPS as recommended by YouTube, and check that your network allows the outgoing connection.
The picture stutters, drops frames, or loses quality
- Check that sustained upload capacity exceeds the configured video bitrate and audio overhead, with margin for normal network variation. A speed test can help identify whether the connection is the constraint.
- Check whether the computer can encode 4K in real time. If it cannot, try a faster preset or a lower frame rate or resolution, then use the matching YouTube bitrate and keyframe settings.
- Make sure the GOP is about two seconds for your output frame rate and does not exceed four seconds. A fixed
-g 60is not appropriate for every frame rate.
The stream is rejected or audio/video is missing
- Check the source’s actual video and audio streams and whether the chosen codecs and pixel/color settings are compatible with your YouTube ingest configuration.
- If stream copying fails, try encoding compatible output rather than
-c copy. If audio is absent, confirm the file has an audio stream before expecting AAC output. - Wait for YouTube’s preview and inspect stream-health messages; change one setting at a time so the cause is identifiable.
The stream is not low latency or viewers cannot select 4K
4K/2160p streams use normal latency on YouTube; the low-latency option is not available for 4K. Viewer playback resolution is not guaranteed by the encoder’s input resolution or bitrate.
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Or let it run in the cloud
If you want the prerecorded loop to keep running without leaving a computer or home connection on, StreamNeo is a YouTube-only cloud service: upload your video, add your YouTube stream key, and go live. It keeps the uploaded video looping from the cloud, with automatic recovery if YouTube drops the stream. Your computer does not need to stay on. Each slot streams the upload as made, up to 4K 60fps, at one price per slot, with no re-encoding or quality tiers. The first day is free with no card. Monthly: $9.99 per month. Start the free first day.
Costs and practical trade-offs
With FFmpeg, there is no service fee for the software in this workflow, but your computer must encode or copy the file continuously and remain powered, and your connection must sustain the upload. Encoding 4K can require substantial processing capacity. Stream copying reduces encoding work only when the source is compatible and does not let you tune bitrate or keyframe spacing. A cloud option shifts the always-on work away from your computer; compare its slot pricing and included storage on the StreamNeo pricing page.
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