Active Format Description

Transform supports Active Format Description (AFD) metadata according to the SMPTE 2016-1 specification. AFD is a standard set of codes that indicate both the aspect ratio of the stream and the active portion (letter box, pillar box) of the image.

AFD codes can appear in multiple locations within a video stream each represented by a different metadata type. See Metadata Types for details.

AFD Insertion

Use the Metadata Processor mplm filter to add AFD metadata to a video stream. The attach operator inserts the metadata into a specific location represented by the root element type.

For example the following composition inserts AFD as ATSC A/72 metadata:

---
input:
  container:
  - name: input
    video:
    - name: v1
output:
  container:
  - name: output
    type: m2ts
    video:
    - route:
        name: v1
      filter:
      - type: mplm
        properties:
          AfdAspectRatio: 1
          AfdValue: 9
          SourceInserters:
          - Type: afdi
      attach:
      - type: 'afd '
        root: a72a

{
  "input": {
    "container": [
      {
        "name": "input",
        "video": [
          {
            "name": "v1"
          }
        ]
      }
    ]
  },
  "output": {
    "container": [
      {
        "name": "output",
        "type": "m2ts",
        "video": [
          {
            "route": {
              "name": "v1"
            },
            "filter": [
              {
                "type": "mplm",
                "properties": {
                  "AfdAspectRatio": 1,
                  "AfdValue": 9,
                  "SourceInserters": [
                    {
                      "Type": "afdi"
                    }
                  ]
                }
              }
            ],
            "attach": [
              {
                "type": "afd ",
                "root": "a72a"
              }
            ]
          }
        ]
      }
    ]
  }
}

Properties

The Metadata Processor mplm filter supports the following AFD properties:

Property	Type	Description
`AfdAspectRatio`	integer	Aspect ratio (AR) of the coded frame: `0` 4:3 `1` 16:9
`AfdValue`	integer	See AFD Codes for details.

AFD Codes

SMPTE 2016-1 defines the following AFD codes:

In a 4:3 coded frame	In a 16:9 coded frame	`AfdValue`
Letterbox 16:9 image, at top of the coded frame.	Full frame 16:9 image, the same as the coded frame.	`2`
Letterbox 14:9 image, at top of the coded frame.	Pillarbox 14:9 image, horizontally centered in the coded frame.	`3`
Letterbox image with an aspect ratio greater than 16:9, vertically centered in the coded frame.	Letterbox image with an aspect ratio greater than 16:9, vertically centered in the coded frame.	`4`
Full frame 4:3 image, the same as the coded frame.	Full frame 16:9 image, the same as the coded frame.	`8`
Full frame 4:3 image, the same as the coded frame.	Pillarbox 4:3 image, horizontally centered in the coded frame.	`9`
Letterbox 16:9 image, vertically centered in the coded frame with all image areas protected.	Full frame 16:9 image, with all image areas protected.	`10`
Letterbox 14:9 image, vertically centered in the coded frame.	Pillarbox 14:9 image, horizontally centered in the coded frame.	`11`
Full frame 4:3 image, with alternative 14:9 center.	Pillarbox 4:3 image, with alternative 14:9 center.	`12`
Full frame 4:3 image, with alternative 14:9 center.	Pillarbox 4:3 image, with alternative 14:9 center.	`13`
Letterbox 16:9 image, with alternative 14:9 center.	Full frame 16:9 image, with alternative 14:9 center.	`14`
Letterbox 16:9 image, with alternative 4:3 center.	Full frame 16:9 image, with alternative 4:3 center.	`15`