Re: Re: About integer64

[Abramo Bagnara <abramo@alsa-project.org>]

Paul Davis wrote:
> 
> >
> >I don't think that's a bad thing to have support for 64 bit integers
> >(perhaps for future use, who knows), but I think that to use this to
> >store a fixed point float is a big mistake.
> >
> >If you think for it you realize that it's *not* an integer and
> >applications are betrayed in their expectation.
> 
> in this case, it *is* an integer. your original question was about why
> its 64 bits - i think that comes from the fixed point internal
> arithmetic. but the end result is a straightforward 64 bit little
> endian integer that needs scaling to get the actual RMS value.

You wrote:

> It seems that the 64 bit-ness comes from it being some
> kind of fixed point representation - the value that you read from the
> registers need scaling (in user space, presumably) by a floating point
> transformation to actually become true RMS values. so its not so much
> they they need 64 bits of precision, more that the hardware needs to
> do the math with this type of data format. keep in mind the
> computation is all being done on a Xilinx FPGA, not a DSP chip, so the
> arithmetic options are (at this time) a bit limited.

What I'm misunderstanding? I tend to interpret the former and the latter
statements in a contradictory way.

-- 
Abramo Bagnara                       mailto:abramo@alsa-project.org

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It sounds good!

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