CurtPalme.com Home Theater Forum

[mp20748]

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[redfox001]

Ok maybe I am wrong and cropping the black bars with a pc (not a scaler) does do something on the pixel mapping.

I do not use a scaler but a pc or mac.

I was thinking that the movie was 1920x817 pixels and that the player added black pixels and that my computer cropped the black pixels.

[mp20748]

[Nashou66]

Ok Let me help you guys out.

All Blu Ray movies that are 2.4 aspect only use 800 lines of resolution for the active video. 2.35 use 817 active lines. 1.78 uses 1080 active lines. So on the non 1.78 aspect movies the area above and below the active image is wasted bandwidth and not needed for that aspect. So not actively scanning the active image is wasting the bandwidth in the PJ and or the scaler. So to tax the PJ electronics less and to free up the bandwidth for any non 1.78 material you would benefit from only having the PJ scan the active area, you loose nothing except unused bandwidth and the non active image( black bars above and below).

One reason many use only 800p even for the 2.35 movies is that it an easily divided resolution and will have less scaling artifacts while do the Active Area Scanning.

Craig explaining it.


http://www.avsforum.com/forum/16-crt-projectors/737385-want-optimize-your-scaler-crt-calculations.html


Also 1:1 pixel mapping will stay intact all you have to do is squeeze the image in the CRT using the V size to get the correct geometry.

On the Marquee, the VDM resistors need to be different value than for 1.78 aspect to get extra adjustment.

[redfox001]

Ok might the whole misunderstanding be in the word cropped? I was not meaning to use a scaler nor did the wolfman. We meaned that the video should be anamorphic send out only the active area. With the CRT we would make the aspect ratio.

In practise this means setting powerstrip to 1920x820 and letting the CRT make it the right aspect ratio.

If I still am wrong than I am missing something and give up as I seem not to be able to understand it. Just make sure we are using the same words and are talking about the same setup.

[jbmeyer13]

This is always a topic that confuses people. For a 2.40AR film the total resolution may be 1920 x 1080 but the active image has a res of 1920 x 800. The vertical res (1080) has 280 lines being used for the black bars which is effectively wasted bandwidth. A lot of people will use a scaler (like a Lumagen) to run a resolution of 1920 x 800p which means that the BW is ONLY being used to display the active image of 1920 x 800.

For example when I run 1920 x 1080p/72 the BW is 200mhz where as if I run 1920 x 800p/72 it's some where between 150-160mhz. This in theory should provide for a cleaner image. MP's point is that once you run 1920 x 800p/72 through the scaler you lose the ability to map the pixels 1:1. Once that happens you are losing information in the signal which reduces the dimensional depth. It comes down to either having a cleaner image with more headroom or having an image with less headroom but contains all the possible image information.

MP has spent a LOT of time pushing the BW limits of the video chain in order to create the headroom necessary to run 1920 x 1080p/72.

[redfox001]

Hmmm while leaving the envelope in tact. That seems to be Mike words. That really would mean leaving 1080 lines with the black bars in tact. That is different from what we are saying in the last three posts.

Question:
Is blu-ray anamorphic? Is there a letterbox added to the blu-ray by the player? Or are the black lines on the disk like Mike says?

[jbmeyer13]

[redfox001]

Yes I do agree with Nash but it seems Mike is saying something different. Perhaps it takes processing for the player to cut the black bars? So with the blackbars there is less processing that needs to be done by a scaler. In the case of a pc I guess the processing is done by the pc.

[Nashou66]

Justin's point about loosing something is not quite right.

Digital signal assign the pixels to a certain point on the map,like a city location in longitude and latitude so to say.

Pretend this map is rubber. When you stretch the unused "dark" portion of the map out of view and cut it off, the now stretched map has things looking too tall . How ever the designated points for the cities on the map have not changed, they still are at the same latitude and longitude. They just look wrong. Now say this Map is on a wall that also is moveable, now you squeeze the wall to un stretch the map to its previous geometry but the unused Dark portion is gone because you discarded it.

So now the designated points have not changed there location on the map so the mapping is still correct .

I hope that analogy helped a little.

Craig could explain it better I might have some points off a little but I think you get the idea.

[jbmeyer13]

[redfox001]

It seems to me we all agree and that The Wolfman is right in making a 817p resolution on his pc? If The Wolfman had a blu ray player he would need a scaler and than Mike's point is valid.

[jbmeyer13]

[redfox001]

He while reading on the internet I find the following opinion:

[redfox001]

[Nashou66]

[redfox001]

I tend to agree as I do not see much processing going on when the pc has to decide if a pixel is black or if a pixel can be let through. One 'if than' statement I do not see how it could make artefacts.

[stridsvognen]

If someone know of a processor who can crop the signal, and keep the source material intact for the active image area, ill love to know what processor to get.

[redfox001]

Ok so you do advise The Wolfman to not make a 817p resolution? I think by now he needs to know

[jbmeyer13]