It all comes down to what wasn’t said. Firstly, HDMI has asked the industry to drop the use of the numbering convention, confusing it may be but at least it gave the industry a way of establishing which version was being referred to.
Secondly, the much heralded phrase “backwardly compatible with your existing HDMI cables” is technically correct, providing you have the high speed Category 2 version of the cable which most of us don’t.
Thirdly there was a distinct lack of discussion concerning the capability of this new version of HDMI, let us call it 2.0 for the sake of this blog, to handle 10 bits along with the improved frame rate of 50/60 fps.
Now this is where the subject gets really complicated and a deeper understanding of what HDMI 2.0 actually refers to is needed. HDMI refers to the connection not the cable, hence allowing the backwards compatible claims for existing cables. HDMI allows a connection of up to 18 Gbps, provided you have the correct speed rated cable. So how do you determine you have the correct cable?
As far as I can determine, the only way you can be certain is to ask to see the manufacturer’s compliance certificate, something I’m sure we are all going to do in the excitement of having just purchased an Ultra HD (4K) screen.
So having established we have the right lead, what about 10-bit support? It would seem with the current version of content protection there is not enough bandwidth to support 10 bits, what a shame. The only hope is for a new version of the HDMI specification, but what would we call it? HDMI 3.0, surely not!
An alternative would be to rework the content protection used on HDMI, known as HDCP, to liberate sufficient bit rate to allow 10-bit carriage, but is this what the industry needs and does it provide adequate protection for valuable content? All will be answered in my next blog where we leave 4K speculation behind us to consider the serious business of content protection.
– Ian Trow, Sr. Director, Emerging Technology & Strategy, Harmonic