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Old 03-18-09, 12:12 PM   #1
LauriM
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Default VDPAU and studio levels (16-235) possible?

Is there an option to stop VDPAU from expanding video to PC levels?

I've been trying to get proper video playback to my TV and found that blacks and whites are crushed. On closer inspection it seems that VDPAU (and software decoding with libavcodec) takes video and expands it from 16-235 to 0-255. This is nice for a PC screen, but TV's are usually calibrated for different levels (black at 16 and white at 235).

Using xine or mythtv this can be fixed using the brightness and contrast controls with a calibration DVD to set proper black and white levels. BtB and WtW are recoverable, but it would be nice to keep the original levels. I'm worried that this kind of adjustment might lead to banding due to inaccuracies.

There's a nice calibration DVD image at http://merifon.altervista.org/TestDVD.html - it also includes some deinterlacing tests in which the NVIDIA does an excellent job.
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Old 03-20-09, 12:17 PM   #2
Stephen Warren
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Default Re: VDPAU and studio levels (16-235) possible?

The standard (default) CSC matrices provided by VDPAU (as part of VdpVideoMixerRender) do convert the video to PC pixel value ranges. You can either use brightness/contrast controls (as you have done) to adjust the CSC matrix, or explicitly provide your own CSC matrix (which would be a good option for an app to have; either explicit TV level option, or custom CSC option). With the appropriate brightness/contrast values, or custom CSC matrix, this should create no loss of original video pixel values.

Hope this helps.
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Old 03-23-09, 05:52 AM   #3
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Default Re: VDPAU and studio levels (16-235) possible?

Stephen, do you think it would be possible to add a matching CSC matrix as predefined matrix into the drivers? - Especially for TV-applications this is a quite common requirement.
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Old 03-24-09, 02:27 PM   #4
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Default Re: VDPAU and studio levels (16-235) possible?

LauriM,

How is your PC connected to your TV (i.e. HDMI, DVI, component, ...). If HDMI, do you have control over RGB full v.s. reduced range on the TV?
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Old 03-24-09, 03:33 PM   #5
jusst
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Default Re: VDPAU and studio levels (16-235) possible?

Stephen, although you directed your question to LauriM I wanted to give a short statement about TV settings.
In my experience there are still several TV screens manufactured which are tied to video level (even through HDMI cables). Higher class LCDs are configurable most times though. Also some screens do some autodetection depending on what device is connected. So in that cases it's best to choose PC/Full range. But for the other cases it would be more than helpful to make VDPAU support this by default.
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Old 03-25-09, 12:43 AM   #6
LauriM
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Default Re: VDPAU and studio levels (16-235) possible?

Quote:
Originally Posted by Stephen Warren View Post
How is your PC connected to your TV (i.e. HDMI, DVI, component, ...). If HDMI, do you have control over RGB full v.s. reduced range on the TV?
Hi Stephen!

I used to have a Panasonic PZ70 plasma (HDMI input) connected to my Gigabyte 9600GT (DVI 2nd head) using a generic DVI->HDMI adapter and HDMI cable. That TV did not allow configuration of RGB levels (pc vs video). It was possible however to adjust the brightness and contrast on the TV to match PC levels without messing up black levels.

I first changed the display adapter to an integrated 9300 as my 9600GT was unable to give exact framerates (23.965 instead of 23.976 etc). I used the mainboard's HDMI output, connected that to my Marantz SR6003 receiver (which passes through HDMI video without video processing). This didn't change the levels, but fixed my framerate problems and gave me HDMI audio. This made the level problem more pronounced though, as now all the video signals arrive on the same TV HDMI input - so all the sources need to give a signal suitable for same TV settings.

I have now upgraded to a Pioneer KRP-500M plasma monitor. It has a setting for PC/video RGB levels, but fortunately I haven't needed that (the all-signals-from-single-input problem..) as the monitor recognizes (or defaults to?) PC levels.


I would like to second jusst's suggestion of adding predefined CSC matrixes to the drivers. Thank you both for your interest in this issue!
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Old 03-25-09, 12:09 PM   #7
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Default Re: VDPAU and studio levels (16-235) possible?

We've performed some investigation into this and here's where we are so far:

a) We've filed an RFE bug covering this general issue. It's on my list, but of course so are 100 other things:-)
b) It isn't appropriate to solve this in VDPAU; it's a system-level issue that also affects 2D/desktop and OpenGL rendering
c) I believe our Windows driver has a control panel option to select YCbCr v.s. RGB PC-range v.s. RGB video-range for output. We'll look into something similar.

Hope this helps!
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Old 03-25-09, 12:27 PM   #8
jusst
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Default Re: VDPAU and studio levels (16-235) possible?

Stephen, of course you're absolutely right with your points. Especially b) is of some relevance. Still for showing some menu system it's not as important to have corret colorspace as it is for video display.
Still having this as a general driver option would be the very best.
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Old 04-22-09, 04:57 PM   #9
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Default Re: VDPAU and studio levels (16-235) possible?

Quote:
Originally Posted by Stephen Warren View Post
c) I believe our Windows driver has a control panel option to select YCbCr v.s. RGB PC-range v.s. RGB video-range for output. We'll look into something similar.
Any news on this or a guess when it might be done?
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Old 04-22-09, 05:36 PM   #10
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Default Re: VDPAU and studio levels (16-235) possible?

No news. I'll post to this thread if/when there's a fix available.
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Old 04-24-09, 11:12 AM   #11
pbjr
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Default Re: VDPAU and studio levels (16-235) possible?

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No news. I'll post to this thread if/when there's a fix available.
Great. Looking (*hoping*) forward for this fix as well.

Thanks
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Old 08-25-09, 08:14 PM   #12
infernix
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Question Re: VDPAU and studio levels (16-235) possible?

Could someone please bump the priority on this?

I've got a Panasonic P50V10E plasma which accepts Video levels (16-235) and I am running XBMC on my Linux HTPC. There is currently no way to get proper output so I'm forced to live with crushed blacks or whites. And I'm not alone, many more people have HDTVs that only accept video level input. Besides, nearly all HDTV content (blu-ray and cable/sat) are in this colorspace, so it would make sense to support this.

The windows driver has it, it shouldn't be very hard to include this in the linux driver I hope?

Thanks!
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