Subject: Re: [linux-audio-dev] matrix model vs. memory
From: Abramo Bagnara (abramo_AT_alsa-project.org)
Date: Sun May 20 2001 - 15:56:05 EEST
Paul Davis wrote:
>
> >> such a port type is important for implementing busses, since
> >> otherwise, you have to have an input port for every object that wants
> >> to connect to it. its very important to me to be able to implement a
> >> "bus" concept easily; an N-channel mixer with a single output port is
> >> a much less efficient way of implementing this.
> >
> >It's not parallelizable on SMP (because lack of atomic float add)
> >without to do some tricks, but that apart I don't see why it's less
> >efficient.
>
> 1) parallelizing audio is non-trivial to begin with. its quite unlike
> parallelizing graphics, for example, because of the temporal
> domain.
Do I've said it's easy? I've said that is feasible and it's feasibility
must not be inhibited by API design.
> 2) its less efficient because the objects sending data to the bus
> could be using "+=" to write into the buffer associated with a pair
> of input+output ports; using the mixer concept, you have to have N
> different input buffers, and sum them at some point before writing
> them to the output buffer.
I'm lost...
>
> >> both of these seem suboptimal to me. as i said, there is already an
> >> implicit matrix of port connections; exposing it and attaching a gain
> >> at each node of the matrix seems like a really cool idea to me.
> >
> >As an *option*, otherwise you limit efficiency also when this is not
> >needed. This would be a symptom of a bad design.
>
> In your own recent message, you mentioned the need for two helper
> functions to transfer data from port to port sometimes. Either they
> includes the concept of gain, or they don't. True?
Yes, but I don't have excluded the possibility to have buffer sharing.
Of course this is feasible only for a subclass of static gain matrix.
-- Abramo Bagnara mailto:abramo_AT_alsa-project.orgOpera Unica Phone: +39.546.656023 Via Emilia Interna, 140 48014 Castel Bolognese (RA) - Italy
ALSA project http://www.alsa-project.org It sounds good!
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