Re: [linux-audio-dev] ALSA API

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Subject: Re: [linux-audio-dev] ALSA API
From: Alexander Ehlert (alexander.ehlert_AT_uni-tuebingen.de)
Date: Wed May 02 2001 - 01:02:17 EEST


Hi,

> its dependent on the h/w. its quite possible that the maestro can't go
> that low. the SBLive can't, thats for sure. in ardour, i just
> use snd_pcm_hw_params_set_period_size(), and it either works or it
> doesn't. the SBLive is the only card I know of so far that doesn't go
> down very far.

humm, I thought so, maybe I have to try with my different soundcards. It's
just because my Hoontech YMF 755 and the maestro go down to exactly the
same values.

> then forget going much below about 100ms on a UP system if you want
> total reliability. on an SMP system with a "free" processor, you can
> probably get down to 10-20ms or so with the regular kernel, proper disk
> drivers, etc.

I actually have no problems with Kernel 2.4.4 with alsa drivers and
oss simulation to get around 10ms.

> in-process plugin (i.e. its in a thread)? or did you mean that they
> run in their own process? if so, then you should be carefully
> following the thread on LAAGA ...

Yes, each plugin is running in its own thread. Nothing like a master or
scheduler copying block after block to each filters. We have even
some plugins using asyncron reads. So it's possible to have feedback
within networks. I haven't followed the LAAGA discussion so far. Just not
enough time, I have to learn for some exams at the moment and so far
I'm quite happy with the Glame plugin. It's actually quite flexibel, you
can transport data in all formats you like. Data is just transported via
buffers. With a small extension you can add any format, just to make sure
that e.g. an fft output port can't connect to a sample input port.
We support FFT, Sample and RMS data by now. I currently thinking about
some sort of Video Protocol. So one could easily write an mpeg2 input
plugin for dvds, extract video and audio streams, operate on audio streams
and sent this into a divx encoder plugin. The gui problem is solved via
properties set by plugins for different parameters. Those properties can
be checked by the gui and widgets are created with libglade. We're still
missing vector parameters for waveshapers, equalizers etc. But that's
no big deal to add.

Cheers, Alex

-- 

The Public is merely a multiplied "me." -- Mark Twain


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