Blackmagic Forum

Ive got a Tentacle Sync --> Camera Mic --> HDMI --> VA, and I can hear the timecode on the VA speaker, but the timecode on the VA isnt syncing to the signal (ive touched the timecode display on the VA and I see "TC" shown), so Im puzzled by the "HDMI Timecode" setting in the settings. The manual (June 2022) states:

"Video Input
Selecting video input will take the embedded timecode from SDI and HDMI sources with
embedded SMPTE RP 188 metadata. This will maintain sync between your SDI or HDMI source
and the file recorded on your video assist."

Is there another way for a camera to send TC over HDMI other than audio that the VA is listening to, but not the audio track?

Perhaps what Im really asking is: What is "embedded SMPTE RP 188 metadata" if its not the audio track information and how is it sent in the HDMI cable/signal?

RP188 TC is embedded on the same wire as the video. The Tentacle is sending LTC. The VA TC input should be set to external.

Good Luck

Note that in addition to setting the Timecode Input option on the Video Assist to External, you will need to feed LTC timecode from the Tentacle Sync directly into the mini-XLR audio input on the Video Assist (rather than into the camera's mic input). Because the Video Assist does not have the ability to read LTC timecode from an audio track included in HDMI input signal.

And of course this will only work with the 7-inch Video Assist models as the 5-inch models do not have an external audio input port.

Thanks all.

I hadn't realized that there were two mechanisms for TC over HDMI signals - one audio (LTC) and one in the video stream itself.

It would be nice if the VA supported audio / LTC over HDMI.

Other than buying another (expensive) Tentacle sync to inject into the VA (my camera doesnt have native TC support), what options are there for getting the TC on the VA sync'd to the camera?

Since LTC timecode is analog audio, you could probably try using a passive 3.5mm TRS splitter (Y-cable) to send the output from the Tentacle Sync to two different places. You could send one 3.5mm output into your camera's mic input (assuming you want to record internally on the camera as well as on the Video Assist).

And then you will need an adapter to go from 3.5mm to mini-XLR to get the timecode signal into the Video Assist. One thing to be aware of with the 3.5mm output from the Tentacle devices is that they are capable of outputting both timecode (on the left channel) and scratch audio (on the right channel). And if you just get a regular 3.5mm to single XLR adapter cable, many of these cables will be wired to combine the left and right audio channels from the 3.5mm connector to produce a mono output signal (since a single XLR cable only carries a single audio channel).

Obviously combining the LTC signal with scratch audio would not produce a good result. So you may want to stick with Tentacle's own 3.5mm adapter cables (or one that you know is wired to only use the left channel or tip of the 3.5mm connector). I don't think Tentacle makes a direct 3.5mm to mini-XLR male (TA3M) cable, but they do make a 3.5mm to full size XLR, which you could pair with an full size to mini-XLR adapter.

Or you could make your own adapter cable pretty easily if you're comfortable with soldering.