Metadata Operators

The following metadata operators can be applied to a video, audio or subtitle stream.

Operator	Type	Description
`detach`	object	Extracts metadata from a media stream.
`attach`	object	Inserts metadata into a media stream.
`merge`	object	Merges metadata from another media stream.

`detach`

The detach operator extracts a specific type of metadata from a media stream. If a root is specified the metadata is extracted from that element type, otherwise the operator searches all root elements.

Property	Type	Description
`type`	string	Four character code identifying the type of metadata to detach.
`root`	string	Four character code identifying the root element.
`filter`	object	A filter that is applied to the stream after the metadata is dettached.

For example the following will extract c708 metadata (CEA-708 captions) from the a72c metadata (ATSC A72 SEI messages):

---
input:
  container:
  - name: input1
    video:
    - name: v1
      detach:
      - type: 'c708'
        root: 'a72c'

{
  "input": {
    "container": [
      {
        "name": "input1",
        "video": [
          {
            "name": "v1",
            "detach": [
              {
                "type": "c708",
                "root": "a72c"
              }
            ]
          }
        ]
      }
    ]
  }
}

`attach`

The attach operator inserts a specific type of metadata into a media stream. The metadata is inserted into a specific root element.

Property	Type	Description
`type`	string	Four character code identifying the type of metadata to attach.
`root`	string	Four character code identifying the root element.
`filter`	object	A filter that is applied to the stream before the metadata is attached.

For example the following copies c708 metadata (CEA-708 captions) from the input rd11 element (SMPTE RDD11 Ancillary Data) to the output a72c element (ATSC A72 SEI messages):

---
input:
  container:
  - name: input1
    video:
    - name: v1
      detach:
      - type: 'c708'
        root: 'rd11'
output:
  container:
  - name: output1
    type: 'mp4 '
    video:
    - route:
        name: v1
      attach:
      - type: 'c708'
        root: 'a72c'

{
  "input": {
    "container": [
      {
        "name": "input1",
        "video": [
          {
            "name": "v1",
            "detach": [
              {
                "type": "c708",
                "root": "rd11"
              }
            ]
          }
        ]
      }
    ]
  },
  "output": {
    "container": [
      {
        "name": "output1",
        "type": "mp4 ",
        "video": [
          {
            "route": {
              "name": "v1"
            },
            "attach": [
              {
                "type": "c708",
                "root": "a72c"
              }
            ]
          }
        ]
      }
    ]
  }
}

`merge`

The merge operator combines the metadata from a source input stream with the metadata in the target input or output stream. This operator is used to:

inject the metadata from a "sidecar" container into a video or audio stream
convert a subtitle stream to the equivalent caption or teletext metadata and inject that metadata into a video stream

Property	Type	Description
`name`	string	Identifies the input stream to merge.
`filter`	array	A list of filters that are applied to the named stream before the metadata is merged.
`combine`	object	Combines multiple subtitle streams (typically containing different languages) into a single stream. The combined subtitle stream is then merged as metadata (typically captions or teletext) into the target stream.

For example the following merges sidecar HDR10+ metadata:

---
input:
  container:
  - name: hdr10plus
    video:
    - name: metadata
  - name: media
    video:
    - name: picture
      merge:
        name: metadata

{
  "input": {
    "container": [
      {
        "name": "hdr10plus",
        "video": [
          {
            "name": "metadata"
          }
        ]
      },
      {
        "name": "media",
        "video": [
          {
            "name": "picture",
            "merge": {
              "name": "metadata"
            }
          }
        ]
      }
    ]
  }
}