captionContainerType property
Use this setting only in DASH output groups that include sidecar TTML or IMSC captions. You specify sidecar captions in a separate output from your audio and video. Choose Raw (RAW) for captions in a single XML file in a raw container. Choose Fragmented MPEG-4 (FRAGMENTED_MP4) for captions in XML format contained within fragmented MP4 files. This set of fragmented MP4 files is separate from your video and audio fragmented MP4 files.
Implementation
final MpdCaptionContainerType? captionContainerType;