RP-NDI-S2038_2021_10

proposal for carriage of SMPTE2038 VANC Data over NDI   DRAFT TBC

This page contains a technical proposal which is not currently a published or formal standard. If you have comments or feedback on the content of this proposal PLEASE contact us with your contribution.

 

This proposal defines a standardised wrapper to carry SMPTE-2038 control messages over NDI by way of a recommended practice technical note.

 

Basic Premise:

When using NDI to carry a stream of content which originated in SDI (with VANC metadata) or MPEG TS (with SMPTE-2038 stream), a mechanism is required to encode this metadata in a form which can be carried along in real time via an NDI stream such that it can be restored as S2308 in transport streams or VANC in SDI for delivery to downstream systems.

 

- The SMPTE-2038 protocol is defined in the SMPTE Standard of the same name.  It describes a mechanism for carrying non specific VANC data within a standardised packet, similar to how a VANC video line can carry arbitrary VANC data, with an ID from a list of official standards.

 

In this proposal, the SMPTE-2038 data is sent using dedicated metadata messages already defined in the NDI Protocol.  It either uses the real time (non frame based) NDI Metadata stream, with SMPTE-2038 message data enclosed, or the video frame attached metadata standard.  Raw SMPTE-2038  message data is encoded in hexadecimal text format before being wrapped in the XML tag.

 

Sent Messages are wrapped in the outer XML tag <S_2038>

 

 

Real Time Free Metadata

NDIlib_metadata_frame_t meta_data

meta_data.p_data =

<S_2038>...........</S_2038>

 

or

 

Video Frame Attached Metadata

ndi_video_frame.p_metadata =

<S_2038>...........</S_2038>

 

 

 

Example : SMPTE-2038  (carriage returns added for visual clarity)

 

<S_2038>

TBC.... WIP

</S_2038>

 

 

The primary objective of this XML schema is to provide a universal and generic mechanism to carry SMPTE-2038 data over NDI, which can ultimately lead to transparent carriage of this data between SDI/TS systems, through NDI and back to SDI/TS.  Whilst in the NDI domain the data can be seen as opaque, or interpreted and processed if required.

 

 

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