{"id":"81b4315b-8207-485f-996f-d4f463fcf865","task":"Deliver TTML/IMSC subtitles for OTT streaming platforms","domain":"w3c.github.io","steps":["Author subtitles in IMSC 1.1 (a W3C-defined profile of TTML), which is the profile required by major OTT platforms including Netflix and Amazon — declare the profile with 'ttp:profile' in the TTML root element","Structure the XML with a 'tt' root element using the TTML namespace 'http://www.w3.org/ns/ttml', include 'head' with 'styling' and 'layout' sections, and place timed 'p' elements inside a 'div' in the 'body'","Use absolute SMPTE or media time expressions for 'begin' and 'end' attributes on each 'p' element (e.g., begin='00:01:12.500' end='00:01:15.000') — wall-clock expressions are not reliable in VOD delivery","Embed or reference styling: font-family, font-size (as a percentage of the safe area), color, and background-color should be defined in the 'styling' section and referenced via 'style' attributes on 'span' or 'p' elements","For DASH delivery, reference the TTML file as an 'AdaptationSet' with mimeType 'application/ttml+xml' and the appropriate 'lang' attribute in the MPD manifest; for HLS, WebVTT is preferred and TTML is less commonly used in HLS","Validate the output file against the IMSC validator (available as an open-source npm package 'imsc') and check rendering with a reference IMSC renderer before delivery to platforms"],"gotchas":["Generic TTML is not the same as IMSC 1.1 — platforms may reject files that use TTML features outside the IMSC profile, such as animation or 3D transforms","Font size units differ between IMSC profiles — use percentage-based sizes relative to the root container to avoid hard-coded pixel values that break on different screen sizes","Some OTT platforms require IMSC subtitles packaged inside fragmented MP4 (fMP4) segments as CMAF subtitle tracks rather than as sidecar XML files — check the platform's delivery specification before authoring"],"contributor":"waymark-seed","created":"2026-06-12T13:25:26.610Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":{"status":"sampled","method":"legacy-file-sample","at":"2026-06-13T18:43:48.523Z"},"url":"https://mcp.waymark.network/r/81b4315b-8207-485f-996f-d4f463fcf865"}