Originally Posted by CraigCooper
Unfortunately HDMI 1.3 can't carry 120Hz at 1920x1080. It will only go as high as 1680x1050.
I know because I am a big gamer who also uses Nvidias 3D Vision and there are no monitors capable of 1920x1080 at 120Hz. We need HDMI 1.4.
Short answer: No and yes and no and maybe. The HDMI 1.3 spec should support it, but almost all cables don't support it, and the HDMI 1.4 spec doesn't improve the situation at all with regards to cable bandwidth. However, we can sort of hope that as HDMI 1.4 spreads that manufacturers will make better cables that actually live up to HDMI 1.3.
Theoretically, HDMI 1.3 does have the bandwidth to support 120Hz at 1920x1080 at 24 bit color depth. HDMI 1.3 specifies 340 MHz signal support, which translates to 10.2 Gbit/s bandwidth for TMDS, of which 8.16 Gbit/s is for video. 120Hz * 1920*1080pixels * 24bits/pixel is 5.971968 Gbit/s. So it should support it; it should even support it in 30bit color, though not 36 or 48 bit deep color spaces.
Practically, almost no HDMI cable really lives up to HDMI 1.3 Category 2 specifications and will do that over runs of any real length. Plenty of cables listed as "HDMI 1.3" are only rated Category 1 (74.25 MHz), not Category 2 (the full 340 MHz). Others that are listed as Category 2 are really only tested over shorter lengths; for the cables actually sold, the manufacturer or vendor will likely do nothing more than test to see that 1080p/60Hz works over the cable run at best. Blue Jeans Cable admits that their best cable only passes full Category 2 testing up to 25 feet, though it will pass 1080p/60 at much longer runs; actually, they boast of this 25 feet, and claim that it beats any other cable on the market. Since this is a projector forum, cable length matters.
Importantly, having the HDMI 1.4 standard won't help
, because it doesn't actually increase the video bandwidth
carried over the cable. HDMI 1.4 does increase the maximum supported resolution
, but if you look, it does so by adding support for higher resolutions at 24/25/30Hz. This is for digital theaters that are showing 24fps movies. Those higher resolutions at 24/25/30Hz don't use any more bandwidth than HDMI 1.3 Category 2 (High Speed HDMI) already supports.See the official HDMI FAQ
, which notes that you'll need an HDMI 1.4 cable with the 100Mbit/s Fast Ethernet connection if you want the data transfer, but otherwise says that "[a]ll of the other new HDMI 1.4 features will be compatible with the existing categories of cables." That includes the new higher resolutions at lower Hz.
Remember that right now
HDMI 1.3 is supposed to support the bandwidth you mention. If you're hoping that HDMI 1.4 means that people will actually start to make HDMI 1.3 Category 2 compliant cables, well, maybe that will happen if people try to actually use deep color and higher resolutions, etc. That's really your only hope, but it doesn't have anything to do with the HDMI spec version 1.4 itself.
It's difficult to sustain that kind of bandwidth over the twisted pair that HDMI uses. Twisted pair is not as suitable for long runs as coax or fiber. Yes, you can run Ethernet at 10Gbit/s over Cat 6 twisted pair cable for runs of up to a hundred meters, and that's a similar bandwidth to what we're asking for HDMI 1.3 Category 2 and HDMI 1.4. But Ethernet (and most protocols sent over Ethernet like TCP/IP) is designed to re-transmit if errors (or collisions) occur, and does so pretty seamlessly to the user. The worst that happens is that errors are converted into slower throughput for the user, which is annoying but better than losing data. With AV, you don't have the option to just resend the pixels if there's an error-- that error just gets displayed on the screen. So your margin for error is much lower. This is a problem of HDMI being designed to be backwards compatible with DVI, and it all goes back to having computer people instead of AV people design the spec, and also support for HDCP being so important.