[pulseaudio-discuss] [PATCH 2/2] core: Add ARM NEON optimized sample conversion code

Arun Raghavan arun.raghavan at collabora.co.uk
Thu Oct 25 01:49:01 PDT 2012

On Thu, 2012-10-25 at 10:19 +0200, Peter Meerwald wrote:
> Hello,
> > > > conversion may be off by one for some samples due to rounding issues
> > > 
> > > I'm not sure about the impact of this. Is there no way to avoid the
> > > rounding error?
> > 
> > Thinking about it some more, I think having sconv be exactly the same
> > across implementations is important. Is this some sort of NEON quirk?
> > >From what I can tell, the result of the vmul is off-by-one.
> I'll have a closer look, certainly interesting; not sure how relevant -- 
> generally don't use floating point if you expect exact results
> on a similar note, I have never checked that floating point speex 
> resampling is sample-exact across platforms/optimization settings

I was poking around this a bit. An input of 0x3f4aaa95 after the
multiplication with 32767.0 should result in 0x46caa8ff but tuns out to
be 0x46caa900. Still trying to figure out why.

-- Arun

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