Developer Information; Blackmagic Video Device Embedded Control Protocol; Overview; Assumptions - Blackmagic Studio Camera Manual Del Usuario

Developer
Information

Developer Information

124

Blackmagic Video Device Embedded Control Protocol

Version 1.0
If you are a software developer you can use the Video Device Embedded Control Protocol to construct devices
that integrate with our products. Here at Blackmagic Design our approach is to open up our protocols and
we eagerly look forward to seeing what you come up with!

Overview

This document describes an extensible protocol for sending a uni-directional stream of small control messages
embedded in the non-active picture region of a digital video stream.
The video stream containing the protocol stream may be broadcast to a number of devices. Device addressing
is used to allow the sender to specify which device each message is directed to.

Assumptions

Alignment and padding constraints are explicitly described in the protocol document. Bit fields are packed
from LSB first. Message groups, individual messages and command headers are defined as, and can be
assumed to be, 32 bit aligned.

Blanking Encoding

A message group is encoded into a SMPTE 291M packet with DID/SDID x51/x53 in the active region of
VANC line 16.

Message Grouping

Up to 32 messages may be concatenated and transmitted in one blanking packet up to a maximum of 255
bytes payload. Under most circumstances, this should allow all messages to be sent with a maximum of one
frame latency.
If the transmitting device queues more bytes of message packets than can be sent in a single frame, it should
use heuristics to determine which packets to prioritise and send immediately. Lower priority messages can
be delayed to later frames, or dropped entirely as appropriate.