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List:       arts
Subject:    Re: Why aRts? When we have ALSA?
From:       Jeff Tranter <tranter () pobox ! com>
Date:       2001-07-15 2:21:58
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Since no one else responded to this, I'll try answering.

On July 14, 2001 03:30 pm, kreuzritter2000 gmx.de wrote:
> What's the point with all this, aRts and alsa?

ALSA is primarily a set of kernel drivers for sound cards, although
with the ALSA library it does some higher level functions too.

aRts is a higher level library that sits on top of the sound drivers.
It provides features like:
- a sound server that allows multiple applications to share hardware services
- a portable (across different hardware and operating systems), object-oriented,
  language-independent set of APIs
- network transparency and authentication
- rich functionality (e.g. flow system for connecting modules, many predefined
  audio modules, codecs for most common audio formats)
- an architecture that can be extended to other streaming media such as
  video

> 2. The next quesion ist the following:
>
>
> In the arts manual handbook it says, that the alsa driver can be used with
> aRts, but only in OSS compatibily mode.
>
> But OSS is only a primitve input/output sound driver architecture that
> doesn't use the special hardware features of good professional soundcards.
>
> So when arts is only using OSS, does this mean that it makes the hardware
> effects of a good soundcard useless?

Yes, when using OSS any sound card features not supported but OSS
won't be used by aRts, although  aRts may provide some of the same functions
less efficiently in software.

There is now an ALSA back-end for OSS, so the statement in the handbook
is no longer correct. If ALSA is present when aRts is built then it should use
the ALSA backend (you may have to specify using ALSA when you start
artsd if OSS is also present). I'm not familiar with the aRts ALSA backend,
so I don't know if it uses any ALSA-specific special hardware features.

> Is it planed to make aRts capable of using the hardware effects of the
> soundcard(by using the alsa-drivers and library) for some effects instead
> of using the arts-software-only modules?
>
> I asked this, because it saves cpu power and doesn't make good soundcards
> obsolute.

That depends on the definition of planned :-) Some features are mapped out
but like most open source projects, the work only gets done if someone
steps forward and volunteers to do it. aRts could make use of more of the
ALSA-specifc features,  but no one has stepped forward to do it.  Since ALSA
is not (yet) in the standard kernel, spending a lot of effort on ALSA-specific
features is probably not a high priority. You would also have to handle the
case where an application wants to use a feature that the sound card is
not capable of (maybe emulate it in software, for example). I also understood
that the ALSA APIs may not be that stable yet, so relying on things that could
change would break aRts.

If you want to look at the code, have a look in CVS at
kdelibs/arts/flowaudioioalsa.cc

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