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First, separate three different goals: adding a WebVTT subtitle track to an FFmpeg-generated HLS playlist, showing captions during a YouTube Live broadcast, or adding subtitles to the replay afterward. FFmpeg can create the HLS subtitle rendition, but that alone is not documented as a way to make captions appear on YouTube Live. For live captions, use YouTube’s embedded EIA-608/CEA-708 route or its supported HTTP caption-feed workflow; for the archive, use YouTube Studio.
Choose the subtitle workflow you need
| Goal | Method | What it does |
|---|---|---|
| A subtitle track in an HLS playlist you control | FFmpeg HLS subtitle rendition | Creates a separate WebVTT rendition associated with a subtitle group in the HLS master playlist. This does not establish that YouTube Live will display it as live captions. |
| Captions visible during YouTube Live | Embedded EIA-608/CEA-708 captions, or a supported software caption feed over HTTP | Delivers captions through a YouTube-documented live-caption path. |
| Subtitles on the uploaded video or replay | YouTube Studio subtitle workflow | Adds a supported subtitle file, such as SRT or WebVTT, to the video. |
The HLS subtitle rendition and YouTube’s live caption feed are different mechanisms. The [FFmpeg HLS documentation](https://ffmpeg.org/ffmpeg-formats.html) demonstrates playlist authoring; [YouTube’s live-caption requirements](https://support.google.com/youtube/answer/3068031?hl=en) describe embedded captions and captions sent over HTTP. The documentation does not verify that a standalone FFmpeg-generated TYPE=SUBTITLES rendition is accepted as captions on YouTube Live.
Add a WebVTT subtitle rendition to an FFmpeg HLS playlist
Use this path when you need a separate subtitle track in an HLS output you control. Your input must contain a text subtitle stream. FFmpeg’s documented example maps video, audio, and subtitles, encodes the subtitle stream as WebVTT, and declares a subtitle group and name in the variant stream map.
- Check the input. Confirm that the source file has a text subtitle stream that FFmpeg can use. A subtitle track that is only burned into the picture is not a separate text stream.
- Map the streams. Include the video, audio, and subtitle streams in the output mapping. Use stream selection appropriate to the input; the exact stream indexes depend on your file.
- Set the subtitle codec to WebVTT. In FFmpeg’s HLS example, the subtitle encoder is specified with
-c:s webvtt. - Declare the subtitle rendition. Configure
-var_stream_mapwith the subtitle group and a name for the track, alongside the video/audio variant mapping. The group association is what links the rendition to the HLS playlist structure. - Inspect the generated playlists. Check that the output contains a WebVTT subtitle rendition and that the master playlist associates it with the intended subtitle group.
FFmpeg’s [Formats Documentation](https://ffmpeg.org/ffmpeg-formats.html) and [Full Documentation](https://www.ffmpeg.org/ffmpeg-all.html) provide the HLS muxer example and options. Treat that example as a playlist-authoring pattern, not a tested command for your particular input, FFmpeg build, or YouTube account. The online documentation is regenerated nightly for the newest revision; if your installed version is older, consult its local documentation through the [FFmpeg documentation index](https://www.ffmpeg.org/documentation.html).
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Show captions during YouTube Live
If viewers need captions while the broadcast is live, configure captions for the live event and use one of YouTube’s documented delivery routes. YouTube says captions may be embedded in the video or sent through supported software that sends captions over HTTP POSTs.
Embedded EIA-608/CEA-708 captions
- In the live setup, enable Closed captions.
- Select Embedded 608/708.
- Configure the encoder to send EIA-608 or CEA-708 captions in the video signal.
- Verify the caption track in the live output rather than assuming an HLS subtitle rendition will be interpreted as embedded captions.
Although the 608/708 standards support up to four language tracks, YouTube’s current help page says it supports one embedded caption track. Plan for one embedded track unless YouTube’s current instructions for your setup say otherwise.
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HTTP caption feed
- Enable captions in the live setup and copy the event’s Captions Ingestion URL.
- Configure supported caption software to send captions to that signed HTTP ingestion URL.
- Check that captions appear during the live broadcast and that the software is connected to the correct event.
YouTube’s help says each stream entry point has one caption feed. It names Total Eclipse, Case CATalyst, CaptionMaker, and StreamText.Net as software options; the page does not establish that these are necessary for an FFmpeg-only workflow or endorse a particular purchase. See [YouTube’s live caption requirements](https://support.google.com/youtube/answer/3068031?hl=en) for current setup details.
If you are sending the video to YouTube over HLS
YouTube’s HLS ingest requirements concern the live video stream, not the delivery of a WebVTT live caption feed. If you choose HLS as the stream protocol in Live Control Room, YouTube’s [HLS setup guidance](https://support.google.com/youtube/answer/10349430?hl=en——————) specifies:
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- Use TS segments.
- Set segment duration to one to four seconds.
- Use a rolling playlist with no more than five outstanding segments.
- Do not use byte ranges.
- Send the stream using HTTPS POST/PUT to the generated ingestion URL.
YouTube notes that HLS has higher latency than RTMP because video is sent in segments. These requirements do not show that a separate FFmpeg HLS subtitle rendition is accepted as a live caption feed.
Add subtitles to the replay or uploaded video
If the goal is to make subtitles available after the stream, use YouTube Studio’s subtitle workflow rather than relying on the HLS playlist. YouTube documents supported subtitle and closed-caption files including SRT and WebVTT, subject to its format rules.
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- Open the video in YouTube Studio and go to its subtitle controls.
- Add a language and upload the prepared subtitle file, or enter subtitles in Studio where available.
- Review timing and text, then save or publish the subtitle track.
See YouTube’s [supported subtitle and closed caption file formats](https://support.google.com/youtube/answer/2734698?hl=en) and [Add subtitles & captions](https://support.google.com/youtube/answer/2734796/add-subtitles-and-captions?hl=en) instructions for accepted formats and the current Studio workflow.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Troubleshoot the common failure points
- No subtitle rendition appears in the HLS output: Confirm the input has a text subtitle stream, that it is mapped, and that the HLS variant map declares the subtitle group. Check the options supported by your installed FFmpeg version.
- The HLS playlist has subtitles, but YouTube Live shows no captions: These are not interchangeable mechanisms. Configure YouTube’s embedded 608/708 captions or supported HTTP caption feed; do not assume the HLS subtitle rendition is ingested as live captions.
- The embedded caption option is unavailable or the track does not show: Confirm Closed captions is enabled, Embedded 608/708 is selected, and the encoder is configured to send the corresponding caption data.
- The HTTP caption feed is not appearing: Confirm the caption software is using the signed Captions Ingestion URL for the correct event and that the stream entry point’s feed is connected.
- HLS video ingest is rejected or unstable: Check TS segment format, one-to-four-second duration, rolling playlist limit, absence of byte ranges, and HTTPS POST/PUT requirements against YouTube’s current HLS instructions.
- Subtitles are missing only from the replay: Add or verify the subtitle track in YouTube Studio; a live caption workflow does not remove the need to manage the archive’s subtitles.
Or let it run in the cloud
If your goal is a 24/7 YouTube channel playing uploaded videos, StreamNeo is a separate option: upload a recording or build a playlist, add your YouTube stream key, and go live. It loops the uploaded videos from the cloud, so nothing has to stay on at home. It streams the upload as made, up to 4K 60fps, at one flat price per slot, and automatically recovers if YouTube drops the stream. The first day is free with no card. Monthly: $9.99 per month. StreamNeo plays uploaded videos to YouTube; it is not a camera-based live-caption workflow, and this does not replace the caption methods above. See StreamNeo or start the free day.
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