[gmpi] Re: Topic 7.1: Channel Formats
- From: "Vincent Burel" <vincent.burel@xxxxxxxxxx>
- To: <gmpi@xxxxxxxxxxxxx>
- Date: Wed, 4 Jun 2003 19:27:53 +0200
Hello
if we are talking about FX plug-in.
i'm more than convinced that we have to fixe the data format (e.g. float32
is perfect ) one time and for ever.
(we have to manage the samplerate , the number of input and output ! it's
enough ! )
if you want to make wrapper, translater, format converter, encoder , decoder
, time stretching , samplerate transformer and so on. please let's do an
other SDK . Because the constraint are not the same and the usage are not
the same .
Vincent Burel
----- Original Message -----
From: <RonKuper@xxxxxxxxxxxx>
To: <gmpi@xxxxxxxxxxxxx>
Sent: Wednesday, June 04, 2003 6:22 PM
Subject: [gmpi] Re: Topic 7.1: Channel Formats
> >>>
> I've not yet seen any convincing arguments or test-cases to support the
need
> for double audio i/o or interleaving.
> <<<
>
> (1) Need for double audio: DSP "kernels" require double precision float
to
> retain sufficient accuracy. A modular synth builder or effects builder
> environment will have processing elements that are in essence DSP kernels,
> such as biquads, delay lines, etc. We should be able to package these
> processing elements as GMPI objects. Therefore, if we don't allow them to
> stream doubles to each, they cannot have the math precision needed.
>
> (1a) Need to not do do double everywhere. Double takes up 2x RAM = 2x L1
> cache as float. For ordinary interconnects, where retained accuracy isn't
> as much an issue, halving the memory footprint equals a performance gain.
>
> (2) Need for interleaving: Surround applications are likely to have
serial
> chains of effects processors that accept multichannel audio. Applying
> volume/pan to a multichannel stream is akin to a vector dot product, where
> one vector is the interleaved sample value and the other is the
per-channel
> gain. Vector dot products can be performed more efficiently, with less
> cache pollution, using SIMD instructions. Therefore, if we don't allow
> interleaving, surround applications are going to suffer degraded
performance
> because they won't be able to fully leverage parallelism -- they will be
> forced to do surround gain as uninterleaved SISD, whose performance has
been
> deprecated on newer Pentium systems.
>
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