[GrnXnham]

Sorry if this is a dumb question. I am new to HDTV.


We just got a Panasonic 50PX80U and I noticed that DVD's produce a sharper image than standard definition cable TV through Comcast. And it's not just some channels, its all of them that are less sharp than a DVD. I don't have digital cable. According to the "info" button, both are 480i. The DVD player is 5 years old so no up-conversion or anything. Why the difference? HD channels produce a sharper image than the DVD's.


When everything goes digital in February will the SD cable produce an image as well as the DVD's?


Thanks

 

[wmcclain]



Quote:
Originally Posted by GrnXnham /forum/post/15447472


Sorry if this is a dumb question. I am new to HDTV.


We just got a Panasonic 50PX80U and I noticed that DVD's produce a sharper image than standard definition cable TV through Comcast. And it's not just some channels, its all of them that are less sharp than a DVD. I don't have digital cable. According to the "info" button, both are 480i. The DVD player is 5 years old so no up-conversion or anything. Why the difference? HD channels produce a sharper image than the DVD's.

I'm not a customer, but I know cable and satelite providers get a lot of grief for poor quality signals and too much compression. DVDs vary in quality too, but when they're good they're very nice. (For standard definition, of course).

Quote:
When everything goes digital in February will the SD cable produce an image as well as the DVD's?

I doubt it.


-Bill

 

[Tulpa]



Quote:
Originally Posted by GrnXnham /forum/post/15447472


When everything goes digital in February will the SD cable produce an image as well as the DVD's?

Not everything is going digital in February. Just the over the air stuff, and really, they're just shutting down the analog. Digital is already being broadcast. Has been for years.


Same with cable, although their analog shutoff will be sometime later (depends on the company.) They're already sending digital signals, which are also in 480i for standard def. Some of it is a tad sharper, but it totally depends on the channel. Don't expect a night and day difference if you go to digital cable, unless you're talking about the HD channels.

 

[joed32]

Isn't it 480i vs 480p?

 

[Tulpa]

DVDs and standard def TV are both 480i.


His DVD player might be converting the signal to 480p, though, depending on which player and TV he has.

 

[GrnXnham]

Thanks for the answers!

 

[ranger999]

Analog cable, just like analog OTA, doesn't have very good resolution. None of the answers here have gotten at a key fact: the transmission system for analog signals doesn't allow for very good horizontal resolution.


Everything being described here is 480i format, including DVD (which has flags per field to assist less-capable deinterlacers with reassembling into 480p frames) so that's not the correct answer why cable looks worse than DVD.


Analog has about 440 distinct "pixels" of horizontal resolution, which is pretty lousy compared to the theoretical maximum of 640 horizontal samples in a digital ATSC SDTV 4:3 frame.


Here's a post I found with a quote from another source describing the limit:

http://forums.howwhatwhy.com/showfla...306246&fpart=1


Look at post #306377 for the mathematics of why a 6 MHz NTSC signal gives you this hard limit. Analog cable uses the same bandwidth per channel.

 

[moparfan]

SD DVD can be quite good provided you have a decent upscaling player and a dvd that doesn't suck. Blows analog cable out of the water and can look good enough that you don't worry too much that your source isn't digital cable or HD.

 

[Princess Aurora]

 http://www.avsforum.com/avs-vb/showthread.php?t=998543