Hdmi-SDI-Hdmi conversion for UHD 10bit

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  • Real Name: David Jones

Hdmi-SDI-Hdmi conversion for UHD 10bit

PostFri Oct 16, 2020 7:08 pm


I'm rather new to sdi extensions on set. With the Blackmagic signal converters, could I send, say, a UHD 10bit signal from a Nikon Z6 through Hdmi-SDI then SDI-Hdmi again into a recorder and not lose anything?

If I've understood correctly, I'd need an 6g converter, to handle UHD, right? But does it bottleneck with 10bit? It'd be maximum 30p.

Also wondering how far the HD signal from the pockets would reach with just Hdmi, only for monitoring from afar. Is 9 meters with good hdmi cable a push?


On a separate side note, hurray for the next Z6 (ii) getting external BRAW! Looks like I'll finally be swapping over to the BM Video Assist from the atomos...

Dave Del Vecchio

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Re: Hdmi-SDI-Hdmi conversion for UHD 10bit

PostSat Oct 17, 2020 8:28 am

Yes, I believe this should be possible. You would need the HDMI to SDI 6G converters to be able to transmit up to 2160p30 video.

Note that SDI video signals are almost always at least 10-bit. This dates back to the standard definition versions of the SDI specifications which specified a 10-bit data stream.

Now, of course it is possible to send an 8-bit video signal down a 10-bit SDI link, but generally speaking, SDI hardware can handle at least 10-bit video signals (most commonly with 4:2:2 sub-sampling). There are some 12-bit 4:4:4 SDI signal formats as well, but these tend to be less widely used and supported than 10-bit 4:2:2.

This is different from the HDMI specifications where 8-bit video signals were the minimum supported format and 10-bit or higher is known as Deep Color, with support for Deep Color varying by hardware.

In terms of the maximum length of an HDMI cable run, it's impossible to give a definitive answer as it depends on the type of HDMI cable used, the signal format, and the sending and receiving hardware. With a traditional passive, copper HDMI cable, the longer the cable distance, the greater the likelihood that you will run into problems. 10 meters is often possible with lower-spec signals, but it really depends on the cable and equipment.

The best bet with longer cable runs over HDMI is generally to use HDMI active optical fiber cables. These can get kind of expensive, but by converting the electrical signals to fiber optic signals for transmission, they eliminate a lot of the cable length limitations of standard passive copper HDMI cables.

Or just convert to SDI for the longer runs.

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