CurtPalme.com Home Theater Forum

**Curt Palme** · Posted: Sun Jan 24, 2010 4:32 pm Post subject: My dumb HD question of the day

So... I was spending some quality reading time in the bathroom this morning, with a copy of the 'Absolute Sound' from 2007, where they reviewed a number of flat screens. THis is the era where many flat screens couldn't accept a full 108p HDMI signal, but the panel itself was 1920 X 1080 and upconversion was done internally.

Reading the specs, I noticed something interesting. All HDMI input specs were 37Mhz for the video bandwidth. Why? Why then are us analog guys trying to find 150Mhz specs, and Mike is modding boards beyond that?

I'm missing something.. what is it?

cmjohnson · Joined: 03 Apr 2006 Posts: 1677

Uh, compression in the codec?

CJ

WanMan · Joined: 19 Mar 2006 Posts: 9668

macgyver655 · Joined: 22 Aug 2007 Posts: 6956

How about the simple explanation. The HDMI speed is a digital signal and the latter is an analog signal.

tse · Joined: 03 May 2006 Posts: 1005 Location: Sweatbucket, Fl.

If the video format is 1080p @ 24Hz the bandwidth will be alot lower than 1080p @ 60Hz. The digital stuff will work with the low refresh inputs.

Scott

**Curt Palme** · Posted: Sun Jan 24, 2010 5:31 pm Post subject:

The specs don't say in the review. Would I be wrong to assume that at say 720p/60, the video bandwidth of a digital set needs to be the same as an RGB analog input?

macgyver655 · Joined: 22 Aug 2007 Posts: 6956

One more time. The speed of HDMI is in Gbit/s............

720p/1080i 8-bit is 742.5 Mbit/s per channel, 1080p 8-bit is 1.65 Gbit/s per channel, 1080p 12-bit DC is 2.23 Gbit/s per channel and so on.

WanMan · Joined: 19 Mar 2006 Posts: 9668

**Curt Palme** · Posted: Mon Jan 25, 2010 3:53 pm Post subject:

Mac, call me stupid, but I still don't understand.

I looked at the review again, and it says: H bandwidth 37 Mhz.

Oh, and this is on component as well as HDMI.

macgyver655 · Joined: 22 Aug 2007 Posts: 6956

**Curt Palme** · Posted: Mon Jan 25, 2010 3:56 pm Post subject:

Let me get it in a bit.

cmjohnson · Joined: 03 Apr 2006 Posts: 1677

Here's another possibility: See all those pins on the HDMI connector? Or DVI connector? There are multiple data streams running on
the cable. Each individual one of them may be no more than 37 MHz but the aggregate bandwidth may be much higher.

CJ