Home » API Reference » Encoding Settings » Captions
Zencoder automatically passes captions through from inputs to outputs, for supported formats. You can also specify a caption file (in SCC format) to add to outputs during transcoding.
Input formats supported for captions:
- MP4/M4V video files that have caption tracks in CEA-608 format
- SCC, DFXP, or SAMI files specified with the caption_url option
Output formats supported for captions:
- MP4/M4V files, with caption track in CEA-608 format
- HLS outputs (segmented outputs with H.264 video in TS format)
Captions can not currently be added to HLS outputs when transmuxing. See prepare_for_segmenting for information.
Note: The following restrictions currently apply to caption conversion:
For DFXP inputs:
- UTF8 encoding is required for all special characters
- Only the first language is converted (the first DIV tag)
- Animation, layout, and region features are not supported
- Styles can be inline or referenced by ID, but only the tts:textAlign property is applied
- Nested DIV and P tags are ignored
- SPAN tags are ignored
- Explicit breaks may be inserted with BR tags
- Only a single caption may be on-screen at any time (subsequent captions will end previous ones)
For SAMI inputs:
- Only the first language listed is converted (the first class-selector style)
- Inline styles are not supported
- Layout-related styling tags (table, div, etc.) are not supported
- Explicit breaks may be inserted by using separate P tags
||URL to an SCC, DFXP, or SAMI caption file to include in the output.
||Don't add or pass through captions to the output file.