AWS Elemental MediaLive
User Guide

Step 3: Match Formats to Categories

There are different procedures to follow to create captions encodes in the output. The correct procedure depends on the "category" that the output captions belong to. There are five categories of captions, described after the table.

On the list of outputs that you have created, make a note of the category that each captions option belongs to.

Captions Format

Category of This Format

ARIB

Object

Burn-in

Burn-in

DVB-Sub

Object

Embedded

Embedded

Embedded+SCTE-20

Embedded

RTMP CaptionInfo

Object

SCTE-20+Embedded

Embedded

SCTE-27 Object
SMPTE-TT Stream in Microsoft Smooth

Teletext

Object

TTML

Sidecar

Web-VTT

Sidecar

For example, your list of outputs might now look like this:

  • Microsoft Smooth output with TTML captions (sidecar) in Czech.

  • Microsoft Smooth output with TTML captions (sidecar) in Polish.

  • HLS output with Web-VTT captions (sidecar) in Czech.

  • HLS output with Web-VTT captions (sidecar) in Polish.

Embedded in Video

The captions are carried inside the video encode, which is itself in an output in the output group. There is only ever one captions asset within that video encode, although that asset might contain captions for several languages.

Captions Object

All the captions encodes for a given output group are in the same output as the corresponding video and audio.

Sidecar

Each captions encode for a given 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 given 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

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.