[opus] configure options for x86

[Jonathan Lennox]

> On Nov 13, 2015, at 4:40 PM, Sean Darcy <seandarcy2 at gmail.com> wrote:
> 
> On Fedora 22, building opus git. There are a number of configure options that I'd like some help on
> 
> --enable-intrinsics, Enable intrinsics optimizations for ARM(float) X86(fixed)
> 
> so this only works on x86 if you're building fixed-point ? If you are, any reason not to enable intrinsics ?

No, this applies on x86 for floating-point as well, now. (I’ve submitted a patch for the configure script to correct this.)


> --enable_rtcd
> 
> Is this only for arm ?

No, it applies to x86 as well. It controls whether Opus will call the cpuid instruction to determine which x86 extensions (sse, sse2, sse4.1, or avx) are supported.


> --enable-float-approx, enable fast approximations for floating point
> 
> does this have a material effect on encoding speed, or quality ?

I don’t know about this one, I’m afraid. But I do know it makes the encoder build in a mode where Infinities and NaNs are ignored, and allows gcc’s -ffast-math option to be used.