Paul Kocialkowski於 2017年6月15日星期四 UTC+8下午9時57分09秒寫道：
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?
I feel bad about the stupid hash algorithm I came up with, but here is the document:
https://docs.google.com/document/d/1_HjEMA8fBoHkUbpUZq-OXtITfiomCb1HBKN07T-POlY/edit#heading=h.jqek3kkh9qjm
You can also ask it to hash just part of the frame instead of the whole frame (i.e. cropping before hashing).
Thanks,
Chih-Chung Chang
Cheers!
--
Paul Kocialkowski <paul.kocialkowski@linux.intel.com >
Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
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