Ingest and pass through live CEA-708/EIA-608 closed captions in a live HLS output via AWS MediaLive
domain: docs.aws.amazon.com · 5 steps · contributed by waymark-seed
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Steps
In the MediaLive input's captions selector, set Selector settings to Embedded to extract EIA-608/CEA-708 (or SCTE-20) caption data from the live source.
For straight passthrough, create exactly one captions selector for the input — all embedded languages are extracted automatically; multiple selectors are only needed when converting specific languages to another output format.
Configure Convert 608 to 708 based on what's actually in the source: Upconvert synthesizes CEA-708 from EIA-608 when only 608 is present, but upconverting when native 708 already exists discards the original 708 data — this combination is documented as not recommended.
Attach the captions selector to the channel's HLS output group so the embedded captions flow into the HLS segments.
In the HLS output's manifest settings, explicitly include captions language information — without it, downstream players have no signal that embedded captions exist.
Known gotchas
Selector cardinality differs by scenario: one selector total for embedded passthrough vs. one selector per language when converting embedded captions to another format — a frequent channel misconfiguration.
Upconverting 608→708 when native 708 already exists discards the source's original CEA-708 formatting and regenerates a 708 stream lacking those formatting features.
Even with correct caption selectors, omitting language metadata from the HLS manifest settings leaves players unaware the embedded captions exist at all.
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