Captions are grouped into five categories, based on how the captions are included in the output.
|
Captions format |
Category of this format |
|---|---|
|
ARIB |
Object-style |
|
Burn-in |
Burn-in |
|
DVB-Sub |
Object-style |
| EBU-TT-D | Sidecar |
|
Embedded |
Embedded |
|
Embedded+SCTE-20 |
Embedded |
|
RTMP CaptionInfo |
Object-style |
|
SCTE-20+Embedded |
Embedded |
| SCTE-27 | Object-style |
| SMPTE-TT | Stream |
|
Teletext |
Object-style |
|
TTML |
Sidecar |
|
WebVTT |
Sidecar |
Embedded captions
The captions are carried inside the video encode, which is itself in an output in the output group. There is only ever one captions entity within that video encode, although that entity might contain captions for up to four languages.
Object-style captions
All the captions encodes for a specific output group are in the same output as the corresponding video and audio.
Sidecar captions
Each captions encode for a specific output group is in its own "captions-only" output. The output group can contain more than one captions output, for example, one for each language.
Each captions-only output becomes a separate file in the packaged output.
Stream
Each captions encode for a specific output group is in its own "captions-only" output. The output group can contain more than one captions output, for example, one for each language.
Each captions-only output becomes a separate stream in the packaged output.
Burn-in captions
The captions are converted into text and then overlaid on the picture directly in the video encode. Strictly speaking, once the overlay occurs, these are not really captions because they are indistinguishable from the video.
