[x265] [PATCH 1 of 2] primitives: added C primitives to compute SSIM

[Aarthi Priya Thirumalai]

As discussed today, we shall have 64bit int and 32 bit int versions of the
primitives for high bit depth and low bit depth cases.


On Sun, Oct 6, 2013 at 12:59 AM, Steve Borho <steve at borho.org> wrote:

>
>
>
> On Fri, Oct 4, 2013 at 11:07 PM, Aarthi Priya Thirumalai <
> aarthi at multicorewareinc.com> wrote:
>
>> I understand. If High_Bit)Depth = 1, you could still choose uint32
>> version for the primitives  but in ssim_end_1(int..) you might get an
>> overflow when bitdepth > 9, as mentioned in the comments there. I could use
>> a 64bit int there for all cases to store intermediary calculations , if you
>> want to remove those if conditions.
>>
>
> If uint64 is big enough for 12bit pixels, then that would be preferable
> over floats, I think.
>
> But we would still want a 32bit int version for the 8bit pixel case, so
> you would still need a run-time decision to pick the right version of the
> function.
>
> Am I misunderstanding the need for the float version? Is it just for
> higher pixel bit depths?
>
> --
> Steve
>
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