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Amazon Elastic Transcoder
Developer Guide (API Version 2012-09-25)

Captions

You can configure Elastic Transcoder to transcode captions, or subtitles, from one format to another. Elastic Transcoder supports two types of captions:

  • Embedded: Embedded captions are included in the same file as the audio and video. Elastic Transcoder supports only one embedded caption per language.

    Valid input formats include CEA-608 (EIA-608, first non-empty channel only), CEA-708 (EIA-708, first non-empty channel only), and mov-text.

    Valid output formats include mov-text (MP4 only) and CEA-708 (MPEG-TS and MP4, 29.97 and 30 frames per second only). CEA-708 captions are embedded in the H.264 SEI user data of the stream.

    Elastic Transcoder supports a maximum of one embedded format per output.

  • Sidecar: Sidecar captions are kept in a separate metadata file from the audio and video data. Sidecar captions require a player that is capable of understanding the relationship between the video file and the sidecar file. Elastic Transcoder supports only one sidecar caption per language, to a maximum of 20 sidecar captions tracks per file.

    Valid input formats include DFXP (first div element only), EBU-TT, SCC, SMPT, SRT, TTML, (first div element only), and WebVTT.

    Valid output formats include DFXP (first div element only), SCC, SRT, and WebVTT.

If you want TTML or SMPTE-TT compatible captions, specify DFXP as your output format.

Elastic Transcoder does not support OCR (Optical Character Recognition), does not accept pictures as a valid input for captions, and is not available for audio-only transcoding. Elastic Transcoder does not preserve text formatting (for example, italics) during the transcoding process.

For information about transcoding captions when you're using the Elastic Transcoder console, see Output Details, Part 3, Caption Settings. For information about transcoding captions when you're using the Elastic Transcoder API, see the documentation about the Create Job API action beginning with the Captions element.

For more information on embedded files, see the Subtitle (caption) Wikipedia page.

For more information on sidecar files, see the Metadata Platform and Sidecar file Wikipedia pages.