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* Pixel-perfect frame checks in IGT Chamelium tests and CRC
@ 2017-06-15 13:57 Paul Kocialkowski
  2017-06-15 17:37 ` Lyude Paul
  2017-06-16  4:08 ` chihchung
  0 siblings, 2 replies; 8+ messages in thread
From: Paul Kocialkowski @ 2017-06-15 13:57 UTC (permalink / raw)
  To: Lyude Paul, chamelium-external; +Cc: intel-gfx

Hi,

So far, there are two ways of testing for pixel-perfect frames using the
Chamelium that are in IGT. The first one grabs a full frame from the Chamelium
and compares it pixel-to-pixel with the cairo reference, which works well for
DP/HDMI.

For VGA, this is probably not the case (because the link is analogue). In that
case, I will look into implementing some fuzzy testing, probably inspired by
what piglit (probably) does to compare output frames with references.

For pixel-perfect testing, grabbing a full frame and testing it with memcmp
comes with a significant time penalty (about 2 seconds for 1080p). The Chamelium
also provides a CRC mechanism that is faster and does not require retrieving the
frame, that IGT currently also supports. It compares the CRC calculated by the
Chamelium (implemented in the HDL) with a hardcoded reference value.

This approach currently fails for me (the values I get don't match the hardcoded
reference). There are reasons why it is not really reasonable: fonts rendering
may change between machines (e.g. use of anti-aliasing) and cairo version
changes could introduce slight rendering changes too (not to mention changes in
the test pattern itself). So instead of comparing the CRC with a hardcoded
reference value, I think it would make a lot more sense to actually calculate
the CRC based on the cairo image that is the actual reference (and that we
should assume may change between runs/machines).

I am currently looking into the CRC calculation mechanism used by the Chamelium
and trying to reproduce it in C code. Is this a known algorithm for which a
reference/optimized implementation exists, or something custom that the folks
over at Google came up with?

Any thoughts, comments or suggestions?

Cheers!

-- 
Paul Kocialkowski <paul.kocialkowski@linux.intel.com>
Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
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^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2017-06-16 10:21 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2017-06-15 13:57 Pixel-perfect frame checks in IGT Chamelium tests and CRC Paul Kocialkowski
2017-06-15 17:37 ` Lyude Paul
2017-06-15 18:38   ` Jani Nikula
2017-06-16  8:32   ` Paul Kocialkowski
2017-06-16  4:08 ` chihchung
2017-06-16  9:28   ` Paul Kocialkowski
2017-06-16 10:09     ` Chih-Chung Chang
2017-06-16 10:21       ` Paul Kocialkowski

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