Captions Settings

Overview

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
• VTT, 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)
• SCC and DFXP formats are also supported with captions type output

For HLS, captions must be mapped to the outputs to get proper in-manifest captions. For example:

{
  "label": "Captions",
  "type": "captions",
  "segmented": true,
  "public": true,
  "filename": "captions.m3u8",
  "caption_url": "PATH_TO_CAPTION_FILE_HERE",
  "streaming_delivery_format": "hls"
}, {
  "filename": "master_playlist.m3u8",
  "type": "playlist",
  "captions": [{
    "path": "Captions/captions.m3u8",
    "language": "en",
    "name": "english"
  }],
  "streams": [{
    "path": "video/video-1800.m3u8",
    "source": "video-res1",
    "audio": "64k_audio"
  }]
}

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

caption_url

API Versions: V1, V2

Parent: outputs

Valid Values: A valid URL to an SCC, DFXP, or SAMI caption file to include in the output

Compatible Job Types: VOD

Example: http://example.com/captions.scc

Description:

The URL to an SCC, DFXP, or SAMI caption file to include in the output.

Zencoder supports captions for multiple output video formats:

• MP4/M4V files, with caption track in CEA-608 format
• HLS outputs (segmented outputs with H.264 video in TS format)

Note: Captioning is not currently supported on transmuxed outputs.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "caption_url": "http://example.com/captions.scc"
    }
  ]
}

See Also: skip_captions and prepare_for_segmenting

skip_captions

API Versions: V2

Parent: outputs

Default: false

Valid Values: true or false

Compatible Job Types: VOD

Example: true

Description:

Don't add or pass through captions to the output file.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "skip_captions": "true"
    }
  ]
}

See Also: caption_url and prepare_for_segmenting