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Discussion Starter · #1 ·
Clearly watching standard definition on any fixed pixel display can be subpar due to scaling issues. I was looking at actual resolutions of the various formats and realized that a 1080 set could actualy double SD resolution (720 x 480) in both directions.... I guess this would be 1:2 pixel mapping. So a single pixel in a 480 signnal would become a symetrical 4 pixel square on the display.


Since in theory it could be mapped in a 1:2 manner creating a 1440 x 960 and still fit on a 1080 set would it not be possible to get a really decent SD picture on a FP 1080 set (granted with bars all around) but no silly scaling issues that make the picture look washed out/soft.


If I am off my rocker please correct me. It just seems that stretching / displaying 480 pixels on a 720 display results in a bad picture because some of the 480 lines get doubled while other do not to fill the 720 line display, but on a 1080 you could double (with a little left over)


Jason
 

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The logic is good, but scalers are pretty effective, so i think mapping isnt really going to add much. Also, this would maybe be a good idea for DVD, but SD over cable or sat is so bit starved, macroblocked, and horrible looking, that its just going to look bad no matter what you do
 

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Discussion Starter · #3 ·
I am not sure I understand why it would look bad if comparing similar sized viewing areas.


For isntance I am currently using a 32" 4:3 tube, if I upgrade to a 42" 16:9 and watch SD window/pillarboxed I am looking at basically the same sized viewing area.


Combine this with a direct 2 to 1 pixel mapping and would the display not be essentailly identical?
 

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You can get really excellant scaling of SD sources from a HTPC using the adaptive deinterlacing available in the free Dscaler program. This adaptive deinterlacing - which simply means that the software dynamicly changes the deinterlacing algorithym for different areas of the screen depending upon the image in that area - is far superior to any hardware deinterlacer in any display or standalone video processor. In fact if you don't have a HTPC for SDTV on your HD display, you are missing a huge chunk of video quality.


Compared to adaptive deinterlacing the simple arithmetic calculations required for resolution scaling are an easy requirement to satisfy. Cheap $200 LCD computer monitors have really good resolution scalers inside - it may still be possible to buy a consumer HDTV with bad resolution scaling, but I don't recall noticing such in over a year. Correctly desinterlacing 480i is a much harder task, particularly for images that originate as video signals versus film.


If you spend any amount of time viewing SDTV, you owe it to yourself to try Dscaler. I use Dscaler on two HTPCs, one is tweeked for my XGA front projector, one for my 1080p LCD. My main HD source is a couple of hundred DirecTV channels, most of which do not have HD versions.


By the way I happen to own a 1440X900 widescreen computer display, a Samsung 940BW. Do you realize such displays are actually 16:10 versus the 16:9 aspect ratio of HDTV? Never fear though, all you do for viewing SDTV in Dscaler with an odd aspect ratio is select the "Square Pixel" option and you will see the SD image scaled as large as possible within the 16:10 screen, at 1200X900 resolution in the case of my Samsung display, with narrow sidebars.


Incidentally my HTPC HD tuner (MyHD MDP-100) displays the resolution of whatever ATSC subchannel it is tuned to. Which is how I happen to know that 4:3 SD subchannels broadcast over ATSC digital signals are actually 640X480 resolution, not 720X480. The 720X480 resolution represents the resolution of NTSC format DVDs. The ATSC standard does allow for broadcast of 16:9 widescreen SD at 704X480 resolution, but I have never seen this - the available SD material is almost exclusively 4:3 aspect ratio material.


When it comes to the inherent analog-to-digital conversion performed by Dscaler, you can select the actual sample rate (aka horizontal resolution) and aspect ratio seperately. I do use 720X480 with 4:3 AR to sample the S-Video from my DSS DirecTiVo receiver.


Gary
 

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Discussion Starter · #5 ·
Gary:


Thanks for the information, I have used DScaler in combination with ffdshow and Zoomplayer for MPEG4 and DVD playback on digital displays, I never though to loop an SD feed into my PC and then scale it before sending it to a digital display. Do you do this process on the fly or do you actually use the HTPC as a DVR, then scale during playback? If this was accomplished on the fly it may meet my needs, in the end I am fairly certain I will have a HTPC as part of my entertainment system for the forseeable future.


While I can see the merits of this I am still confused why 2:1 pixel mapping cant be employed where every pixel in the SD broadcast becomes 4 on the "high res" digital panel. Assuming the viewing area is the same between the 2:1 scaled SD 4:3 picture on a digital display and a 4:3 tube TV would they not look almost the same?


I understand that advanced scaling techniques are used in many digital displays but it seems SD pictures still look horrible, way to soft and blurry and I dont attribute this to size.
 

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LCD screens dont have dithering, things like macroblocks are more noticeable than on an CRT.
 

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Quote:
Originally Posted by Gary McCoy /forum/post/0


You can get really excellant scaling of SD sources from a HTPC using the adaptive deinterlacing available in the free Dscaler program. This adaptive deinterlacing - which simply means that the software dynamicly changes the deinterlacing algorithym for different areas of the screen depending upon the image in that area - is far superior to any hardware deinterlacer in any display or standalone video processor. In fact if you don't have a HTPC for SDTV on your HD display, you are missing a huge chunk of video quality.


Compared to adaptive deinterlacing the simple arithmetic calculations required for resolution scaling are an easy requirement to satisfy. Cheap $200 LCD computer monitors have really good resolution scalers inside - it may still be possible to buy a consumer HDTV with bad resolution scaling, but I don't recall noticing such in over a year. Correctly desinterlacing 480i is a much harder task, particularly for images that originate as video signals versus film.


If you spend any amount of time viewing SDTV, you owe it to yourself to try Dscaler. I use Dscaler on two HTPCs, one is tweeked for my XGA front projector, one for my 1080p LCD. My main HD source is a couple of hundred DirecTV channels, most of which do not have HD versions.


By the way I happen to own a 1440X900 widescreen computer display, a Samsung 940BW. Do you realize such displays are actually 16:10 versus the 16:9 aspect ratio of HDTV? Never fear though, all you do for viewing SDTV in Dscaler with an odd aspect ratio is select the "Square Pixel" option and you will see the SD image scaled as large as possible within the 16:10 screen, at 1200X900 resolution in the case of my Samsung display, with narrow sidebars.


Incidentally my HTPC HD tuner (MyHD MDP-100) displays the resolution of whatever ATSC subchannel it is tuned to. Which is how I happen to know that 4:3 SD subchannels broadcast over ATSC digital signals are actually 640X480 resolution, not 720X480. The 720X480 resolution represents the resolution of NTSC format DVDs. The ATSC standard does allow for broadcast of 16:9 widescreen SD at 704X480 resolution, but I have never seen this - the available SD material is almost exclusively 4:3 aspect ratio material.


When it comes to the inherent analog-to-digital conversion performed by Dscaler, you can select the actual sample rate (aka horizontal resolution) and aspect ratio seperately. I do use 720X480 with 4:3 AR to sample the S-Video from my DSS DirecTiVo receiver.


Gary


this pc program I gather the pc need to be and running this program to make SD signals look better.... and what exactly would be needed to do all this?
 

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Dscaler is an application that runs with an analog tuner card. I use a Hauppauge WinTV with my HTPC. Here's the download site with the supported hardware list:

http://www.dscaler.org/


..in case it's not obvious, Dscaler 4 is the thread for 480i and Dscaler 5 is the thread for 1080i.


Gary
 
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