Re: Is there any real advantage to having an HDMI port?

On 2007-08-21 09:44:44 -0600, The alMIGHTY N <natlee75@xxxxxxxxx> said:
Okay, sounds good. I did note that Alvy Ray Smith's argument was more
geared towards broadcast television, which I don't believe to act
exactly the same as television signals.

Broadcast TV signals (well, analog ones, at least), are designed to be more or less identical to what a CRT needs to drive its coils (and therefore draw the screen) All things told, there is not a lot of difference between the various analog inputs (it all comes down to 'how much information is being crammed down how many wires').

To display a digital signal on a CRT, it takes some extra circuitry to convert the framebuffer to a signal the CRT can use. I seem to recall seeing a few papers where HDMI actually looked /worse/ than component on most CRT displays. (Caused by the manufacturer cutting cost by putting crappy parts in the digital->analog converter)

DLP, LCD, and Plasma displays don't need to do this signal conversion; they just display the framebuffer directly.

What about high-definition movies? Would these act differently than
broadcast television, video games, or both?

Unfortunately, the answer here is 'maybe'. I would expect an HD DVD of a 'made for TV movie' to be an interlaced recording, and could potentially suffer from the same problems Alvy Ray Smith mentions. Part of the HD DVD (and Blu-ray) spec is the ability to put the recording on the disc in whatever format was the original; so if it's an interlaced recording, it will go onto the disc as an interlaced recording. If it's a progressive source, it will go onto the disc progressive.

Because there are only 24 FPS to a (film) movie, you don't run into the problems mentioned by Alvy Ray Smith. (Unless, of course, you've figured out a way to get an additional 36 frames out of thin air; in his argument, you really are getting 60 fps (at lower resolution). It's a case of 'can't get something from nothing'. So for movies, interlacing (and then deinterlacing) is a lossless process. The final image is the same on either interlaced or progressive.

The image is stored on disc as 1080p (progressive sources compress a bit better than interlaced ones). The player then looks at what the display can output, looks at user-defined player settings, whether it's necessary to convert from 24 FPS -> 30 FPS, etc., and then uses that to figure out what to give the display.

Video games can actually go either way. If the display *can't* do progressive, there are options. The console can do either full-frame interlacing (where both fields of come from the same frame), or it can do the vertical/temporal resolution tradeoff, and get a higher framerate by using a different frame for each field. I don't develop for the xbox, so I don't know if it's even possible to do the second option -- but my computer graphics experience outside of consoles makes me think you can't. So video games are in more or less the same boat as film-based movies. (The big difference is film is *always* the exact same framerate. The framerate in a single game is constantly changing.)

.

Relevant Pages

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