Subject: Re: [linux-audio-dev] API for Input / Output plugins
From: Paul Davis (paul_AT_linuxaudiosystems.com)
Date: Wed May 12 2004 - 01:01:04 EEST
> Besides I see around the LADSPA API for sound processing but nothing si
>milar
>for input / output.
there are good reasons for that.
> However, what about writing an advanced API for I/O plugins, completely
>detached from other programs ( as Xmms ), potentially multiplatform, to suit
>the needs of the big part of audio programs? I mean, a plugin written for a
there are fundamentally different approaches to handling i/o when it
involves hardware. one of them is based on the traditional unix
read/write model, the other is based on a callback/interrupt
model. its not easy to reconcile these models. in fact, its basically
impossible without adding lots of buffering and thus killing latency
performance.
portaudio *does* support ALSA, but only in CVS. thats as close as you
will get to a "standard". ALSA and OSS both provide (or maybe i should
say, tend to result in the use of) the read/write model. JACK,
CoreAudio, ASIO/EASI/GDIF and PortAudio all require the
callback/interrupt model (more or less, anyway).
choosing between these two models makes a phenomenal difference to the
design of your overall application. its not a choice to be taken
lightly, and you can't move back and forth between the two models with
ease.
now, take a look at the list of apps that support JACK
(http://jackit.sf.net/apps). then consider that JACK supports ALSA and
OSS on Linux and CoreAudio on OS X, and ask yourself "do you feel
lucky?" :)))
>certain API ( i.e. ALSA, OSS, Jack, OsX etc... ) will be usable for all other
>applications with all advantages of a plugin architecture and standard
>code... Input plugins are important too: I see lot of apps rewriting
>continuosly Ogg, Mp3 or Wav support in any kind of flavour, but not always
>reusable code. About writing it once for all?
for audio file I/O, libsndfile takes care of that rather nicely, thank
you, and there are an ever growing number of programs that use it. its
even gaining popularity in the non-linux world. its hard to see any
reason to even think about a different API.
--p
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