SDI video coming out of cameras can trigger the video recorder to start and stop via ancillary packets usually contained in the HANC space. I've found the ARRI specification for this packet in their white paper Metadata_in_the_ALEXA.pdf, but not all recorders work with it. Where to find the packet specification for Sony, Red and/or Panasonic?


After contacting a manufacturer, I found out that a popular way to flag record is to set the MSB bit of binary group 1 of the RP188 timecode ancillary packet.

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I couldn't find specific details, but it appears that ancillary data on SDI in general conforms to SMPTE 291M. I couldn't find any details about the specific implementations used for deck control. It appears like there could potentially be some variation between manufacturers or even particular decks since the ancillary space doesn't seem to be that regulated other than specifying what it shouldn't step on with the main signal.

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    Thanks AJ, I did find another way some camera manufacturers like RED signal record: a bit in the RP188 timecode ancillary packet - the MSB of binary group 1. Jun 3, 2013 at 21:15

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