Re: [linux-audio-dev] LADSPA 2

From: Florian Schmidt <mista.tapas@email-addr-hidden>
Date: Sun Apr 23 2006 - 14:10:55 EEST

On Sat, 22 Apr 2006 10:53:58 +0100
Steve Harris <S.W.Harris@email-addr-hidden> wrote:

> Almost two years ago at the LA conference a bunch of us agreed that
> something need to be done to improve LADSPA, and on the approximate
> direction it should take.
>
> Anyway, I finally got round to making a sketch plugin and .h file:
> http://plugin.org.uk/ladspa2/

Hi,

thanks for taking the initiative on this! I would like to see a way for
the host to pass its native buffer size to the plugin though. I know,
this is really kind of contrary to how LADSPA is supposed to work (i.e.
the run () function should be able to handle an arbitrary number of
frames), but it has some serious advantages for fft-based algorithms.
And i think it should be possible to merge the two approaches somewhat.

A hint which the plugin could set that it needs power of two periodsizes
for optimal operation would be nice, too. The host should be free to
ignore this and the plugin should still work (doing what it sees fit.
i.e. use non power of two fft window sizes or use double buffering
again), but at least the host could notify the user that this plugin
might work suboptimal.

The approach of chopping up the period into smaller chunks (i.e. to
update control data at non period boundaries) would still be available,
but the plugin should be able to rely on the chunks being i.e. in this
form:

---> time
|128 |128 |
| | | | | | | | |

Native buffer size being 128 frames [upper row] and the lower row is how
it is chopped up [as an example]. We see that all chopped up chunks add
up to the native period size. This enables an fft based plugin to
collect data over a whole period and do its stuff once for all these
samples, without the need for extra double buffering which is a problem
with current ladspa and dssi.

There would be an additional requirement put on the host: It has to use
a fixed underlying buffersize [optimally a power of two] even if it's
not bound to do this by the hardware/soundinterface it uses. I.e. a host
that does the processing freewheeling.

What do you think?

Flo

-- 
Palimm Palimm!
http://tapas.affenbande.org
Received on Sun Apr 23 16:15:01 2006

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