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Wednesday, January 3, 2007

Connecting Systems To Displays: HDMI 1.3 Counter-Points

This blog post references my cover story 'Connecting Systems To Displays: What We Got Here Is A Failure To Communicate' in EDN's January 4, 2007 edition.

In my article, I point out that it's not absolutely necessary to upgrade to HDMI 1.3-cogniscent multimedia sources, destinations and in-between cabling in order to enjoy high-resolution audio in Dolby TrueHD and DTS-HD Master Audio formats. As I put it:

HDMI Version 1.3 also broadens audio-transport support to encompass the latest high-fidelity lossless-compression formats from Dolby Labs and DTS. This addition is significant only if the transmitting device is incapable of decoding these formats; if it can decode these formats, it could alternatively employ the support for uncompressed audio transport in earlier HDMI versions, along with multichannel-analog-audio connections.

In a letter to the editor in the January 2007 issue (#116) of Widescreen Review, Microsoft's Kevin Collins echoes this point and expands on it, revealing several good reasons why you might not want to rely on a downstream A/V receiver to do the decoding even if the HDMI transport and audio destination both support this feature:

Another point to keep in mind is that if the audio is not decoded in the player, then none of the interactivity that utilizes sound can be achieved. This means that the PIP that people are coming to love with IME and U-Control would not be possible. The audio must be decoded in the player and mixed with the audio from the secondary video. Another advantage of decoding in the player with next-generation audio codecs is that they have meta-data that the studio, while authoring, can control the down-mixing and fold-down with.

I'll close with another HDMI 1.3 qualifier. Over and over again I see Sony's PS3 marketing fingerprints when I read that someone has claimed that HDMI 1.3 is required in order to support 1080p60 (1080-line resolution, progressive-scan, 60 fps) images. This is simply not true; the original HDMI 165 Mpixel/sec bandwidth was more than adequate to handle this display setting. Do the math yourself if you don't believe me (1920x1080x60=124,416,000 pixels/sec). When you see, for example, a first-generation Toshiba HD-A1 HD DVD player whose HDMI video output tops out at 1080i, that's simply because the HDMI transmitter inside the player is incapable of running at peak HDMI speeds. Again quoting from my article, specifically about HDMI's predecessor, DVI (the point also applies to the HDMI successor):

However, some silicon suppliers, particularly those that attempted to integrate a DVI transceiver within a larger piece of silicon such as a graphics chip, were unable to meet the 165-MHz design target. (DVI’s I²Cbased DDC (display-data-channel) bus is the means by which graphics chips and displays communicate their respective capabilities and limitations to each other.)

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