Brightness Level (1 Viewer)

[jeedepee]

Hi kszabo,

Which graphics card do you have? I have the CLUB3D HD 2600PRO and I'm curious if the solution/workaround of switching back to catalyst 7.6 will work for my card as well, since I have problems with black-level, contrast etc. in Mediaportal too.

 

[bigj]

Apparently the correct way to compensate is at the display side.
i.e. you accept that the device (HTPC) is outputing whatever it is and then adjust your TV/Projector so that <16 is absolute black and > 235 is over white.

The problem is that with an HTPC which is designed with other content (the GUI) authored to use full 0:255 you'd loose detail in dark GUI artwork and clamp the bright bits.

The solution is to either author (or blit adjust) GUI for 16:235, which is unlikely! or to bite the bullet and expand the VMR texture from 16:235 to full 0:255. I hope MPII provides D3D colour transformations (brightness, contrast) that will allow this.

The reason for using the device to adjust: Supposedly the expansion from 16:235 to 0:255 at the source end introduces banding. But I've not done any tests to confirm how bad this is (over allowing the device to do it.) Perhaps the device has >8bit precision or has analog expansion? Anyway, at the end of the day I can't really see any alternative but to expand the VMR source for an HTPC.

And I wonder if/why overlay expansion would be any better in this scenario (of overlay window within a GUI) - i.e. If using DVI then isn't that 8bit channel? so even overlay video over GUI is still 8bit total precision surely...(with the overlay content just being expanded from 16:235 to 0:255)?

 

[kszabo]

Apparently the correct way to compensate is at the display side.

I don´t know... I use CoreAVC for h.264 playback. I can set "input level" to "TV (16-235)" and output level to "PC (0-255)". With this setting I get good picture. This sounds correct for me (it is the same correction that the display would do if I let it). We just need good codecs which can handle videos with TV-levels and expand it to 0-255., like CoreAVC 1.6.5.

Correcting on display side is not a good idea IMO because:
- other applications, GUI would be too dark (as you said)
- few TVs support switching 0-255/16-235 (mine does NOT), so this is not even possible

The 3rd solution like postprocessing with ffdshow ("levels" filter) I don´t use, because I could not use HW acceleretion with it (I like the avivo deinterlacing very much)

Feedepee:
I use ATi x1250 onboard
I use Vista, and using EVR did not help at all in having correct level expansion (as some say)
h.264 HD material works with CoreAVC, set as above (nice black and contrast)
mpg2 (DVD, normal SDTV) works good with ATi decoder, HW accelerated, black corrected in Catalyst Control Center/Avivo settings (brightness set to appr. -18, contrast appr. +120).
Other apps, desktop und MP Gui remains normal like that.

 

[Darre]

I found using EVR in vista to be the best sollution, but for some reason all I get is black screen when I use it under xp

I have .net framework 3 and 3.5 so the problems must be elsewhere.. For now my sollution is having coreavc/ffdshow alter the colors so its not all grey at least.

 

[jeedepee]

Yesterday, I installed the catalyst 7.6 driver and my problem seems to be solved and I did not discover any disadvantage so far.

 

[bigj]

Apparently the correct way to compensate is at the display side.

I don´t know... I use CoreAVC for h.264 playback. I can set "input level" to "TV (16-235)" and output level to "PC (0-255)". With this setting I get good picture. This sounds correct for me (it is the same correction that the display would do if I let it).

Well that is my thought. The only (maybe) benefit of letting display do it is that expanding in analog domain or with >8 bit precision may be better. e.g. say a notional display expands to 16bit then it would expand 16-235 by linear interpolation to a range with (smooth) 64K steps. But if you do it source side on the PC in 8bits then you can only expand to 256 steps, and this would then be expanded *again* on display side to 64K. I think this double expansion/quantisation may lead to theoretical artifacts. But if it *is* there it is a) dependent on exactly what the display does, b) probably pretty marginal anyway. All the same, people do talk of banding...

- few TVs support switching 0-255/16-235 (mine does NOT), so this is not even possible

You can achieve the expansion using contrast and brigtness adjustments, which pretty much all displays support!

The 3rd solution like postprocessing with ffdshow ("levels" filter) I don´t use, because I could not use HW acceleretion with it (I like the avivo deinterlacing very much)

Agreed, HW acceleration is too important.

At the end of the day I agree that expansion on source side is the only option for HTPC. And to be honest I think the argument about banding is overstated - I still can't see that overlay (or EVR) expansion is any different and people seem to think that's the bees knees...

 

[Spragleknas]

I found using EVR in vista to be the best sollution, but for some reason all I get is black screen when I use it under xp

I have .net framework 3 and 3.5 so the problems must be elsewhere.. For now my sollution is having coreavc/ffdshow alter the colors so its not all grey at least.

I belive you have to uncheck all VMR9-options in setup. Did you try this?

 

[kszabo]

Yesterday, I installed the catalyst 7.6 driver and my problem seems to be solved and I did not discover any disadvantage so far.

I need overscan correction (PC connected to Pana plasma through HDMI), and this is supported after 7.8. No other advanteges/disadvantages are known to me (but this one is important for me). But I could assume that there are constant developement of Avivo features (better HW acc, support of newer chips etc).

I found using EVR in vista to be the best sollution, but for some reason all I get is black screen when I use it under xp

EVR gives me same gray problem as VMR9 (Vista x1250 Catalyst 7.12) and preview does not work if I fast fw/rev DVDs or TV (mpg2). VMR9 exclusive mode works very good (no tearing etc )

 

[Darre]

I found using EVR in vista to be the best sollution, but for some reason all I get is black screen when I use it under xp

I have .net framework 3 and 3.5 so the problems must be elsewhere.. For now my sollution is having coreavc/ffdshow alter the colors so its not all grey at least.

I belive you have to uncheck all VMR9-options in setup. Did you try this?

I hadn't - but now I have and there's no change.. I get sound but the screen is totally black.

 

[kszabo]

I hadn't - but now I have and there's no change.. I get sound but the screen is totally black.

It should make no difference. Enabling EVR disables VMR9 (MP ignores all VMR settings, a portal developer wrote it somewhere I am pretty sure).

Black screen with audio sounds like video codec issue. I had it sometimes myself. Just install ffdshow, open video decoder configuration, under "codecs" right click onto decoder column of one format and "set all stable formats to libav codec" (after this I deactivate h.264 to be able to use CoreAVC for this). Hope this helps.