Reduced image quality with XBMC v12.3 (probably not XBMC related)
#1
Not sure if this problem has its root cause in the XBMC code, but I'll give it a go and explain it anyway as this is where the issue is noticeable.

I'm currently running XBMC v12.3 (latest released package on Arch Linux, xbmc 12.3-14) on a Mac Mini MACMD387HA with Intel HD Graphics 4000. Ever since I upgraded from the (arch linux) xbmc 12.3-1 package, I have experienced graphical issues in one way or another. My X Server version is 1.15.0 (package xorg-server 1.15.0-5) and the xf86-video-intel driver 2.99.911 (package xf86-video-intel 2.99.911-2).

From package 12.3-1 to 12.3-3 I began to experience horizontal tearing (there is a bug post regarding this issue here). I cannot pinpoint whether this is caused by Xorg or XBMC - but as the problem was solved by adding the following in my Xorg config file, it suggests that something happened in the former.

PHP Code:
Section "Device"
    
Option "TearFree" "True"
EndSection 

According to the intel man file, this "TearFree" option forces X to perform all rendering to a back-buffer prior to updating the actual display, so side-effects are additional output latency, memory usage and processing capacity.

That was the back story. I have now updated to a newer package of xbmc (xbmc 12.3-14) and I have started experiencing other graphical issues. Not tearing, but I have noticed that the image quality has taken a hit to the worse. This is especially noticeable in scenes where the camera is in a fixed position and there is little to no movement in the picture. What then happens is that the image is become more blurry/soft as time progresses. The problem disappears when the camera starts moving or the scene/angle changes.

I have no idea on how to troubleshoot this further, so I stand humble before you fellow xbmcians for ideas on solving this matter.[/quote]
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#2
Disable backing store. TearFree is not what you want. Search the forum it was answered multiple times now.
First decide what functions / features you expect from a system. Then decide for the hardware. Don't waste your money on crap.
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#3
(2014-04-09, 21:10)fritsch Wrote: Disable backing store.
I have already tried this. Added the following to my X11 configuration file:

PHP Code:
Section "Device"
        
Identifier "Intel Graphics"
        
Driver "intel"
        
Option  "BackingStore"  "0"
EndSection 

Confirmed that it was disabled by checking Xorg.0.log.
PHP Code:
[174010.890] (==) Depth 24 pixmap format is 32 bpp
[174010.891] (IIintel(0): SNA initialized with Ivybridge (gen7gt2backend
[174010.891] (**) intel(0): Option "BackingStore" "0"
[174010.891] (**) intel(0): Backing store disabled 

When I disabled the backing store, I did not experience anything different. The image quality progressively gets worse in scenes with limited movement (especially noticeable around eye/nose area). Also with backing store disabled and also TearFree disabled, the tearing issues are back with horizontal lines being drawn in scenes with rapid movement.

Any other ideas?
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#4
Logfile please. From what you tell, e.g. "lines" (more than one) that looks like non working deinterlacing.
First decide what functions / features you expect from a system. Then decide for the hardware. Don't waste your money on crap.
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#5
Sorry for not being more specific. There is (in all observed cases so far) only one line at the time, and it appears at locations in the picture where there is movement. As for the progressively reduced image quality, this happens in locations in the picture where there is little to no movement (i.e. the quality of the static area gets worse for every second passed until the camera changes the angle, the scene changes, or there is more rapid movement).

The video I am using for testing, h264_720p_hp_5.1_6mbps_ac3_unstyled_subs_planet.mkv (planet), can be found here: http://www.auby.no/files/video_tests/

At 00:46, I notice that the upper part of the planet becomes more "clouded" (blurred) as time progresses.

When the camera is moving up at 00:58, I notice the horizontal line just around the mountainous areas.

Log files are available here:
Xorg.0.log
xbmc.log
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#6
To make that fully sure: Your Vertical Blank Sync is set to "Always Enabled" or better "Let driver decide" (needs xbmc restart)?

Edit: Also a full log would be nice, to see if xbmc is "arch" patched.
First decide what functions / features you expect from a system. Then decide for the hardware. Don't waste your money on crap.
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#7
Vertical Blank Sync is set to "Let driver decide" (needs xbmc restart).

Full logs are added (from xbmc startup and until the video playback finished). If you are curious about the custom linux kernel, it is a modified version of the arch linux kernel with a patch that I needed to avoid my Apple Trackpad causing a kernel panic. That patch only affected the following files, net/bluetooth/hidp/core.c and net/bluetooth/hidp/hidp.h, so it should not have any effect on this video issue.

xbmc.log
Xorg.0.log
bluetooth kernel patch
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#8
You are using a patched Xbmc that has been compiled with external libraries.
Try a vanilla Gotham mainline build.
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#9
And if you are at it. Upgrade to v13 - use the aur git patckages and remove the --enable-external-libraries and remove the comment about our ffmpeg handling ...
First decide what functions / features you expect from a system. Then decide for the hardware. Don't waste your money on crap.
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Reduced image quality with XBMC v12.3 (probably not XBMC related)1