video DAC speed of DVD player (1 Viewer)

[Will.MA]

I'm in the market to upgrade DVD players and I see wide variance in the video DAC ratings. Most newer models are 10 bit/54 MHz, but I've come across a few that are 12/108. The chips look like northbridge/southbridge chips on a PC motherboard. If they are at all similar, make and speed of the chips make a HUGE difference in system performance. Is this analogy remotely valid? If not, how important are the video DAC ratings?

 

[Rob Kramer]

Not very.


What IS important are the chips that perfrom the MPEG decoding, the de-interlacing, and the scaling (3 different chipsets).

 

[Will.MA]

Rob, thanks for the sparce, if not somewhat trite, response. Would you mind elaborating a little more? It would seem that greater digigal "bandwidth" (I don't know if this is the right term) would result in a player capable of higher resolution. Logically the speed of the converter should impact how quickly the conversion can be performed. Perhaps this would result in a more-detailed picture & sound with rapid attack and response? I mean I'm just a layman consumer but it makes sense. If not, then why do manufacturers publicize the speed/make of the chips if that information isn't significant? Are there many chips that DON'T perform MPEG decoding, the de-interlacing, and the scaling? Isn't each video function vitally essential for viewing DVD titles? Finally, what is the significance of chip speed?

I haven't replied to your post solely to debate your response. I'm looking for information so that I can make an informed purchase. Your contribution would be more helpful if you went further past one and two-word replies and substantiated your input for those readers like myself that are new to the hobby. I'm simply trying to solicit a little more detail. Thank you.

 

[BrianWoerndle]

The reason the spped of the chips is not as important anymore because they are all oversmapling anyway. Interlace video runs at 13mhz. Progressive runs at 27mhz. So a 54mhz chip already is twice as fast as you need. A 108mhz chip is 4 times faster than you need. As you know with computers, having more overhead can help make sure the player doesn't drop any information, but that is rare.

"Are there many chips that DON'T perform MPEG decoding, the de-interlacing, and the scaling?"

The chips in question are the MPEG decoders. But speed is one of the least important factors, just like different northbridge/southbridge chipsets perform very differently. Almost all DVD players now have de-interlacer chips to turn an interlaced signal into progressive scan. Some cheap DVD players will combine that in with the MPEG chip giving it even more to do. The scaling chip is only in the DVD players that upconvert the signal to 720p or 1080i and is not necessary at all. The only benefit is for displays that have a native 720p or 1080i resolution. It is better to let the DVD player handle the scaling in the digital realm instead of the TV.

 

[Will.MA]

Thank you for the insightful information and patient explanation Brian. If I might indulge you a tad further, what are 2:3 & 3:2 pulldowns? Under what conditions would they be useful?

-WA

 

[Rob Kramer]

WA

The three chipsets that I listed are the "weak links" in the system. VDACs have progressed far beyond what is actually needed. We are at a point now where we are seeing errors, anomilies, etc releated to the "supporting" chipsets (and other design factors).

Please read the series of articles here:
http://www.hometheaterhifi.com/volum...on-9-2000.html

More specifically:

http://www.hometheaterhifi.com/volum...eo-9-2000.html

and

http://www.hometheaterhifi.com/volum...e-10-2000.html

and

http://www.hometheaterhifi.com/volum...ug-4-2001.html

 

[BrianWoerndle]

"Thank you for the insightful information and patient explanation Brian. If I might indulge you a tad further, what are 2:3 & 3:2 pulldowns? Under what conditions would they be useful?"

The short answer:
TVs run at 30 frames per seconds, film is shot at 24 frames per second. 3:2 pulldown is the process of concerting the film rate into the TV's. (I am oversimplifing here) It basically uses 3 of frame 1, then 2 of frame 2, 3 of frame 3, 2 of frame 4... (they are really interlaced frames, which are half frames, but that is a whole different discussion) In the end the math adds up.

There are websites that give much greater detail and accuracy, but this should give you the idea.

 

[Will.MA]

Rob,
The links you suggested pretty much cleared up any questions I had about DVD transports. Thanks for pointing me in that direction. Although the learning curve can be high for the unintiated, I'd recommend it to all of those that seek to make an informed purchase decision.

-WMA

 

[matt-f]

Just to add, there is also 216MHz/11-bit DACs now too. Basically what comes so is whatever has been already mentioned above.

matt