Caption Support Comes to Cloudflare Stream Live
Cloudflare is expanding caption support in its Stream product. While on-demand videos have supported captions for years, live streams will soon be able to carry embedded captions directly to viewers. The company has announced that Stream Live will auto-detect captions in incoming live streams ingested via SRT or RTMPS, and include them in the delivered manifest file.
How It Works
Stream Live scans incoming live streams for CEA-608 and CEA-708 captions. If the source stream contains captions, no additional configuration is needed on the customer side—the captions are simply passed through to the output manifest.
- Stream Player users: Captions are rendered automatically by the player.
- Custom player users: Captions require enabling display settings in your own player implementation.
Language Support and Post-Event Options
During a live event, Stream Live supports captions for a single language. Once the live event concludes and becomes an on-demand video, you can upload caption files in multiple languages. This two-phase approach means caption language coverage can be expanded post-event even when it was limited during the broadcast itself.
CEA-608 and CEA-708: Legacy and Modern Standards
Closed captions have evolved significantly since their introduction. Open captions—overlaid directly onto the video picture—were the norm in 1973 and could not be turned off. Closed captions arrived in 1982, transmitted via a separate feed and rendered by television sets rather than imprinted on the image itself.
CEA-608 (Line 21) and CEA-708 define how captions are transmitted. CEA-708 is the newer standard, bringing broader language coverage and text positioning capabilities that CEA-608 lacks.
Availability
Live caption support enters closed beta next month. Cloudflare intends to add automatic live caption generation in the future, but for now customers must provide captions in their source streams.
