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HDMI-SDI micro converter and latency

PostPosted: Wed Oct 28, 2020 1:18 pm
by Peter Bouthoorn
How much latency does the SDI-HDMI micro converter add?

We currently have 2 Sony SRG-300SE ptz cameras connected to an ATEM 1 M/E through SDI. We're planning to buy a 3rd Sony SRG camera, but the SDI version of the SRG-300SE is no longer available. The newer SRG models all have 4K and our out of our price range. So now we're considering buying the HDMI version of the SRG300 (which is still available) and use it in combination with the HDMI-SDI micro converter.

Are there any other concerns in this setup beside latency that we should be aware of?

Re: HDMI-SDI mini converter and latency

PostPosted: Wed Oct 28, 2020 10:07 pm
As far as I know, any piece of HDMI in your signal chain will cause latency - only a clean SDI signal chain will be latency-free.

Re: HDMI-SDI micro converter and latency

PostPosted: Thu Oct 29, 2020 1:58 am
by Dave Del Vecchio
The latency of the micro converters is on the order of a few lines of video, which is a fraction of a millisecond, so fairly negligible for most purposes. Most of the Blackmagic video converters have very little latency unless they are doing scaling or frame rate conversion (like the UpDownCross HD or some of the Teranex units).

In terms of HDMI vs. SDI, as far as I am aware, there is no inherent difference in latency between the two signal formats. Both are clocked wire level signal formats that send video data at the bandwidth that is necessary for the selected frame rate and resolution.

Among cameras I have used that have both HDMI and SDI outputs, I have not generally noticed a difference in the output latency between the two ports.

I would guess that any belief that HDMI has more latency stems from the fact that HDMI is more often used in lower-end and more consumer-oriented video hardware. And minimizing latency is often less of a concern in these types of devices than in devices designed for professional live video applications. This is particularly an issue with a lot of consumer-oriented cameras which often have several frames of latency on their HDMI outputs. But that output latency is due to the design and internal processing of the camera rather than the type video output port in the camera.

Re: HDMI-SDI micro converter and latency

PostPosted: Thu Oct 29, 2020 11:08 am
by Peter Bouthoorn
Thanks a lot for sharing this information. A fraction of a microsecond is indeed negligible for our purposes.

Re: HDMI-SDI micro converter and latency

PostPosted: Thu Oct 29, 2020 11:18 am
Thanks Dave for the clarification. I work with prosumer hardware, hence my experience with latency.