[Bug 99247] glReadPixels on Intel N3700 (Braswell) slower than Raspberry Pi

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99247

--- Comment #10 from Jason Ekstrand <jason at jlekstrand.net> ---
(In reply to Pierre Proske from comment #9)
> Thanks for investigating!
> 
> I'm happy to use RGBA if that is the fastest path, I had no idea RGB was so
> troublesome.

Yeah... Turns out that hardware really likes pixels to have nicely aligned
addresses.

> It would still be great to see this fixed but if I can immediately get
> better fps using RGBA then I will do that :)

Even if we get faster RGB paths implemented, they won't be as fast as RGBA.  So
you're probably better off doing RGBA anyway.  Specifically, you probably want
to use GL_UNSIGNED_BYTE and GL_RGBA in your glReadPixels call.  If you ask for
the data to be returned in RGB then we have to pack it and that's slow.

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