[_Shorty]

I just downloaded the 2014-01-29 nightly build of gotham and immediately I notice that the brightness is off now in my videos. Black is way too bright, making everything look washed out. It looks like it's probably the same difference as seen in the UI when you toggle between using 16-235 or not. Is there some 16-235 processing going on in the decoder/playback code that is independent of the UI 16-235 limited range setting? Something that does not exist in Frodo? Recalibrating my TV just for gotham does not seem like the right "fix" for this problem.

[Martijn]

don't post in development please. moved it.

[_Shorty]

Whoops, sorry about that. May have gone back to the wrong tab in the browser before posting, apparently.

[_Shorty]

This still existed in Gotham Beta 1, and still exists in Gotham Beta 2. I've noticed something different when I was checking it out this time. I have a DVD with a few test images on it that I tried this time. I did not test with a DVD before, only with files such as H.264/mkv videos. DVD playback does not seem to be affected by this bug. It only seems to happen when I'm playing back a file.

Today I noticed beta 2 was released, and I completely missed that beta 1 was released. I did, however, test with both beta 1 and 2 today and both still show the same problem that the earlier daily builds showed. Today I even dragged over the laptop and colorimeter to get some numbers for how bright the blacks are showing with Gotham versus Frodo.

Frodo: 0.018 fL
Gotham 0.383 fL

I even took a little video to do a demo of it. http://www.youtube.com/watch?v=KynVEW3BtRw

That was with a 720p mkv of the first episode of Homeland, which shows a black brackground with white text in the middle. But as I say, with a DVD source instead, the measurements for Frodo and Gotham match each other with both showing practically the same number for the same black test image. I'm wondering if the debug logs contain enough/relevant information to show why there is a difference between Frodo and Gotham. Is it worth running the same tests again with each version to get the logs? I certainly don't mind if you want them.

Another thing I noticed is there definitely seems to be something triggering a switch to the limited colour range once playback begins. This is a TV show that happens to be 24 fps, and I have XBMC set to pause for a short amount of time to wait for the TV to finish switching refresh rates. Usually I have that set to wait 2.0 seconds before playback begins, but if I set it to something longer like 5 or 6 seconds then I can tell that it is only once playback starts that the switch to limited colour range seems to happen.

If I set it to 5.0 seconds just to test, once the TV has finished switching modes the picture does indeed look just as black/dark as it usually does with Frodo, but once that delay is finished and the actual video playback begins it immediately goes grey instead of black. That leads me to believe that the limited colour range option is turning on at the moment playback begins, even though that option is turned off in the settings.

I am only pointing that out to show that the switch to limited colour range happens when playback begins. I do not think it is related to refresh rates or framerate, as when I play some files that do not cause a refresh rate change, such as some 30fps TV shows, the same problem still exists. The 24 fps / 24 Hz change with that show just allows us to extend that pause/delay feature to see that the black remains normal during the selected pause period, but once playback begins the black turns grey.

[jmarshall]

One presumes you've done the obvious thing and used your colorimeter on both displaying a dark screen without video playback. You can use the screen calibration for this probably.

That should confirm that the colour change is happening only during playback.

Have you tried fiddling with the settings in the video OSD while playing a video? These are per-video settings, and if the 'default' for that is set incorrectly, it could well cause this behaviour.

[_Shorty]

Well, I'm sure it's easy enough to set that delay for refresh rate change to something more than long enough to take a reading of the black screen that appears during that delay. I'd be more than happy to do so, but I'm confident it isn't going to give me any new info. As I say, if I set it to 5 seconds now then I can see quite clearly that the black being shown during the delay is just as black as the black during Frodo playback. Then once the delay ends and playback begins, it turns to grey.

<a few minutes later>
And I have taken a measurement of the black during the delay now, and while it is waiting for playback to start it showed a 0.014 reading, and then once playback started I paused it at the same location as before and the reading was similar to before at 0.364. The screen is clearly black to the eye during that delay, and then once it is over it is quite noticeably grey.

I can confirm the problem with any number of shows I try, if I can find a black portion anyway, so I don't think it is due to one or two videos here and there just happening to have the brightness/contrast set differently. I just checked the Homeland one I tested in the youtube clip to see if it was still set at 50/50, and it was still at the default 50/50. I have never changed those settings for any videos, by the way, so I doubt my settings database is going to contain any changes for a video here and there. Was worth checking to make sure, though.

I just checked a handful of random files to see what happens, and some of the files were not affected. Those all seemed to be SD files in avi containers, I think. I think I'll find/make a few sample files to test with and see if it might just be related to certain containers or codecs. I would imagine the code for handling avi and mpg is a lot older than the code for mov/mp4/mkv, and the latter seems at the moment to be where the problem is showing up. I don't know that SD vs HD will make any difference, but I could check that too. I'll see if I can check this stuff today sometime. That Homeland opening is a nice and easy test subject. Perhaps I'll just see what happens with a few re-encodings of that in different containers, since it makes for an easy measurement.

[jmarshall]

What do you actually have set for the limited colour range setting?

By the looks there may be an issue under DXVA that it potentially applies it twice (once at decode, once at render?) which could cause what you see, assuming you actually have that setting enabled ofcourse.

Otherwise, try without DXVA, and please do get logs with the DVD playback (that apparently doesn't show the issue) and an mkv or whatever. SD vs HD shouldn't make any difference whatsoever.

[Piers]

Although I may not have equipment to prove it, my eyes are good enough for me. I've noticed a change in brightness on Gotham as well.

These posts mention the exact same issue:

http://forum.xbmc.org/showthread.php?tid=188260
http://forum.xbmc.org/showthread.php?tid=190113

I have all the usual settings enabled and have made no changes to drivers or anything else on the HTPC.

[jmarshall]

Jinx - please test software decoding

[_Shorty]

I have the limited colour range setting turned off, since I don't think I need it for my TV. If I turn it on the problem just gets worse and appears, as you say, to be applying the limit twice. I am using DXVA, and I don't think my CPU in that machine is even fast enough to play HD content without it. I had to switch from WinXP on that box to Win7 just to start using XBMC, since it didn't use DXVA under WinXP. For this testing it shouldn't matter, since I'll be pausing playback to take a measurement. But under normal circumstances I *need* DXVA or that machine is rendered useless, hehe. I'll get a pair of logs for you in a little while. Just heading out for a bite to eat at the moment.

[_Shorty]

I did test software decoding just now before I head out the door. It does measure the same black during playback as Frodo. So I'm guessing DXVA mode is applying the limited colour range even though it shouldn't because that setting is turned off.

[jmarshall]

As far as I can tell, DXVA doesn't do anything particularly special here when limited colour range is set to off. It does if it's set to on (potentially applying twice).

[_Shorty]

Well, it certainly seems to be behaving as though it were turned on once I start seeing video playback. It should be noted that the UI's colour range doesn't appear to change or be affected, and it is only the video playback that seems to have the change applied. Here are the logs I just collected.

xbmc-frodo-dvd
http://pastebin.com/W4gqMJNY

xbmc-frodo-mkv
http://pastebin.com/TciKrWhH

xbmc-gotham-dvd
http://pastebin.com/WvcunKk0

xbmc-gotham-mkv
http://pastebin.com/PsLbiE4A

[jmarshall]

Have you tried switching from DXVA-HD to DXVA (render method) ?

[_Shorty]

I've always just had that on auto-select. Just tried switching between DXVA and DXVA-HD to see if there was any difference. With it set for DXVA it seems to be behaving just like Frodo with correct black levels. With it set to DXVA-HD the black is all out of whack again.

edit - I'm assuming DXVA-HD doesn't really add anything imperative.