Blackmagicdesign Blackmagic Cinema Camera, Installation And Operation Manual

Page: 398 / 409

Developer Information
Blackmagic SDI Camera Control Protocol
Version 1.1
If you are a software developer you can use the SDI Camera 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
The Blackmagic SDI Camera Control Protocol is used by ATEM switchers, Blackmagic 3G-SDI Arduino
Shield and Blackmagic Camera Remote to provide Camera Control functionality with supported
Blackmagic Design cameras. Please refer to the ‘ Understanding Studio Camera Control ’ chapter
section of this manual, or the ATEM Switchers Manual and SDK manual for more information. These
can be downloaded at www.blackmagicdesign.com/support.
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 prioritize and send immediately. Lower priority
messages can be delayed to later frames, or dropped entirely as appropriate.
Abstract Message Packet Format
Every message packet consists of a three byte header followed by an optional variable length data
block. The maximum packet size is 64 bytes.
Destination device (uint8)
Device addresses are represented as an 8 bit unsigned integer. Individual
devices are numbered 0 through 254 with the value 255 reserved to
indicate a broadcast message to all devices.
Command length (uint8)
The command length is an 8 bit unsigned integer which specifies the
length of the included command data. The length does NOT include the
length of the header or any trailing padding bytes.
377 377 Developer Information