As integrators, we all know about HDMI and its idiosyncrasies. The extenders are hit or miss. HDCP or EDID drop off over distance. Pink sparkles come and go. Sequence of powering on devices has to be exact to get a handshake.
You cross your fingers every time you hit a button on a matrix switch when the screens fade to black, hoping the newly selected source will appear.
So is HDMI our friend or our foe? The promise of one simplified connection for HD video and audio seemed, at first, like an advantage for us, and HDCP eased Hollywood’s anxiety about a video Napster killing their revenues.
But has that promise really been delivered? Could it have been delivered better in a different way and still accomplished the same goals? HDMI was a data guy’s solution to a video problem.
Let’s dissect the arguments and explore the alternatives.
Resolution: 1080P and Beyond
The first argument typically waged is that we needed something that could transmit 1080p/60. However, we know that commercial broadcast equipment and theater gear handle these resolutions fine. They do it digitally as well on coax over an SDI connection.
Now HD-SDI did require two connections for HDMI’s single plug, at least at HDMIs introduction, but know a 3G-SDI connection can do the same with a single connector (there is also a rumored XD-SDI spec that goes well beyond). SDI uses a locking BNC interface so the cables don’t unplug (HDMI hasn’t required that yet), uses coax for transmission, and can go up to 1000 feet.
Sure, 3G-SDI carries HD video and eliminates our concerns about connectors separating and signals not traveling longer distances, but HDMI carries audio. Well, for the uninitiated, the SDI protocols also carry audio, 16 and 32 channels in the HD and 3G variants, to be exact.
OK, so SDI can handle bandwidth and audio, but we hear that Hollywood wanted encryption so this would never work. To that I offer this example: A digital server at a theater has a hardware component inside that uses a FIPS 140 security protocol that codes the Digital Cinema Package (DCP) or the movie if you will to the server. It is a combination of hardware and software that assures that movie is played on that machine. To make a long explanation short, the cinema projectors they connect to are HDCP and SNMP compliant and do not have HDMI ports.
If you do jobs with DVI connections, you know HDMI was not necessary to transmit EDID.
Video & Data
EDID and HDCP are separate from video and come through as separate. They aren’t inseparable. We know this well, as the two Cat5 versions of HDMI extenders typically break out audio/video on one Cat5 and the EDID and HDCP on the other (to oversimplify, have mercy on me Jeff Boccaccio, president of DPL Labs). So if SDI can transmit the A/V information, we would just need to isolate some existing type of protocol, cable, and connector that could carry data back and forth, maybe over a twisted pair and an RJ45 plug.
How many of you would gladly terminate seven mini coax for RGBHV and digital audio than deal with the HDMI migraines you have experienced in the last few years? Now take into account that SDI would require 1-2 coax terminations for high res and maybe a data connection for EDID and HDCP.
HDMI is a complex and ever-evolving technology that is at the heart of today’s digital entertainment.