You may not need to convert the file at all: OBS Media Source supports WebM and has a Loop option. If your software or workflow requires MP4, use FFmpeg to re-encode the WebM to H.264 video and AAC audio, then test the result in the software that will run the loop. Converting a video file and configuring YouTube’s live encoder are separate steps.
Check whether your live-loop software needs MP4
For a local OBS loop, try the WebM file directly before converting it. OBS’s Media Source documentation lists WebM as a supported format and provides a Loop setting, which replays the file after playback finishes.
- In OBS, add or select a Media Source and choose the WebM file.
- Enable Loop in the source properties.
- Preview playback through the end and back to the beginning. If the file plays correctly and the transition is acceptable, conversion is unnecessary.
If your encoder, editing workflow, or playback software requires an MP4, convert it rather than changing the filename. Renaming video.webm to video.mp4 does not change the codecs or container contents.
Convert WebM to MP4 with FFmpeg
For a broadly compatible MP4 starting point, re-encode the video to H.264 and audio to AAC:
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ffmpeg -i input.webm -c:v libx264 -pix_fmt yuv420p -crf 20 -preset medium -c:a aac -b:a 192k -ar 48000 -movflags +faststart output.mp4Replace input.webm and output.mp4 with your actual filenames. Install FFmpeg first if it is not available in your terminal, and run the command from the folder containing the input file or use full file paths.
What the options do
-i input.webmselects the source file.-c:v libx264encodes the video as H.264.-pix_fmt yuv420pchooses a widely compatible pixel format.-crf 20sets a quality target for x264; lower values generally mean higher quality and larger files. It is an example, not a YouTube requirement.-preset mediumbalances encoding speed and compression efficiency. A slower preset can take longer; a faster preset can produce a larger file at a similar quality target.-c:a aac -b:a 192k -ar 48000encodes audio as AAC at the example bitrate and sample rate. Adjust the bitrate to suit the source and intended use.-movflags +faststartmoves MP4 metadata toward the beginning of the file for progressive playback.
The command re-encodes both streams, so it takes processing time and may alter quality. The CRF, preset, and audio bitrate are adjustable examples, not prescribed YouTube settings. YouTube’s upload encoding recommendations specify MP4 and H.264 video, and list AAC-LC among the audio options; these are upload-oriented recommendations, not live-ingest settings.
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When stream copy is worth trying
FFmpeg can put existing streams into a new container without re-encoding. The FFmpeg documentation describes stream copy as useful for changing the container or container-level metadata. It is fast and avoids additional encoding loss, but it does not change the source codecs or apply filters. A stream copy may fail or produce a file that the target software cannot use if the source streams are not suitable for the MP4 container or workflow.
ffmpeg -i input.webm -c copy output.mp4Try this only when preserving the original streams is appropriate. Check the resulting file’s codecs and open it in the software that will play it. If the command fails, or playback compatibility is the goal, use the H.264/AAC re-encode instead.
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Verify the converted file and the loop
Before using the file in a live broadcast, open the MP4 in the exact software that will run the loop. This practical check can catch file or playback problems before they reach viewers.
- Confirm picture and audio both play.
- Watch the end-to-start transition; a visible jump or brief pause may come from the edit itself.
- Check that audio does not stop early, drift, or restart awkwardly when the video loops.
- Confirm the software can play the file continuously for the duration you need.
Configure YouTube live ingest separately
Converting the prerecorded file does not configure the encoder sending your live stream. For RTMP/RTMPS ingest, YouTube’s live encoder settings list H.264, H.265, and AV1 video; AAC or MP3 audio; constant bitrate (CBR) encoding; and a recommended keyframe interval of 2 seconds, not over 4 seconds. Configure these in the live encoder, not in the file-conversion command.
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Test with audio and movement similar to the intended broadcast, check the Live Control Room preview, and monitor stream health. YouTube’s streaming tips recommend leaving 20% upload-bandwidth headroom above the total stream bitrate. A file that plays properly on your computer does not by itself establish that the live ingest is healthy.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Copyright and reused-content checks for a documentary loop
Using a file you can play is not the same as having permission to broadcast it. Before looping a documentary or excerpt, confirm that you hold the necessary rights or have a license that covers public live streaming, including its music, footage, and other incorporated material. YouTube may detect copyrighted material in live streams; consult YouTube’s copyright guidance and the applicable license terms for your content.
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Also consider monetization separately from copyright permission. YouTube’s channel monetization policies assess reused content at the channel level; permission to use material does not automatically establish eligibility for monetization. A loop should not be treated as a shortcut around originality or policy requirements.
Or let it run in the cloud
If your goal is to keep a prerecorded video live on YouTube around the clock, StreamNeo is a cloud option rather than a local OBS conversion workflow. Its three-step setup is: upload a recording or build a playlist, add your YouTube stream key once, and go live. StreamNeo loops uploaded videos; it does not stream from a camera.
- Your computer and home connection do not need to stay on.
- Videos stream as uploaded, at any quality up to 4K 60fps, for one flat price per slot.
- Automatic recovery is included if YouTube drops the stream.
- The first day is free with no card, once per account. Monthly is $9.99 per month.
See StreamNeo or compare plan lengths. To try the free first day, start a StreamNeo account.
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