[Intel-gfx] Pixel-perfect frame checks in IGT Chamelium tests and CRC

[chihchung at google.com]

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 at linux.intel.com> 
> Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo 
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/intel-gfx/attachments/20170615/2460c035/attachment.html>