Serial ADM is a new professional audio metadata format derived from ADM as specified in Recommendation ITU-R BS.2076. Serial ADM enables a new set of use-cases aimed at supporting next generation audio features such as:

• Immersive audio
• Dialogue enhancement
• Multi-Language and audio-description support
• Commentary/Dialogue selection and adjustment
• Audio-object movement
• Headphone virtualization

Serial ADM is specified in Recommendation ITU-R BS.2125, which describes how the ADM XML document is placed into a serial frame-based structure.
A sequence of Serial ADM frames is called a flow. The ADM metadata carried by a flow can be separated into two groups:

• Time variant dynamic metadata
• Time invariant static metadata

A Serial ADM flow can use one of the following flow types:

• Full-Frame - supports random access on every frame
• Intermediate-Frame - does not support random access
• Mixed-Frame - supports random access but not on every frame 
• Divided-Frame - supports random access on some frames with data-rate smoothing

A Serial ADM metadata authoring application can select the appropriate flow type for the application. Situations where immediate random access is important may use Full-Frame mode whereas other applications where data-rate considerations are more important may use Divided-Frame mode.

Carriage of Serial ADM has so far been specified for:

• Interfaces that use AES3 with SMPTE ST 337 formatting. This is documented in SMPTE ST 2116:2019.
• Interfaces that use SMPTE ST 2110-41. This is documented in SMPTE ST 2127-2

Documents

• Recommendation ITU-R BS.2076 Audio Definition Model
• Recommendation ITU-R BS.2125 A serial representation of the Audio Definition Model
• ST 2116:2019 - SMPTE Standard - Format for Non-PCM Audio and Data in AES3 — Carriage of Metadata of Serial ADM (Audio Definition Model)
• ST 2110-41, Professional Media Over Managed IP Networks — Fast Metadata Framework
• ST 2127-2, Mapping Metadata-Guided Audio (MGA) Mapping MGA Audio Metadata to ST 2110-41

Code

Dolby has made available source code for applications and tools that support Serial ADM. These tools are available under an open-source license.

• PMD Tool provides an authoring and conversion applications with a library for external use. PMD Tool is available on Github.
• AM Viewer is a monitoring application that can display Serial ADM when carried over SMPTE ST 2110-31 . AM Viewer is available on Github or Pypi.