On Fri, 20 Apr 2001, Paul Davis wrote:
>>Could you provide a url for aes? I'd like to check it out. What's it all about
> there is no URL. currently, the source for 99% of the program is in
> Quasimodo CVS, accessible via the download page at
> http://quasimodo.org/. its the quasimodo/libs/audioengine module.
I think we should definititely at least try the pure plugin based audio
server approach. Like with LADSPA, I think what we need here is a
concrete, short and sweet API proposal (preferably in C).
And it doesn't necessarily need to be very complex...:
--
LAAGA - Linux Audio Application Glue API
1. Design overview
- client applications (ones that produce audio data) are
compiled as dynamicly loadable plugins (libraries)
- server application works by reading audio data from
input-plugins and audio hardware (=soundcard), and
writing to output-plugins and audio hardware
- audio data is transfered between server and clients
using functions calls performed by the server
2. Function callback APIs
2.1 Client side
- open/close (initialize/cleanup)
- read(int channel_id, ...)
- write(-- " --)
- prepare/start/stop/pause
- set_block_size()
- ... probably a few others
2.2 Server side (functions passed during client.open(&server_funcs))
- add_channel
- remove_channel
- ...?
3. Possible problems
- negotiating the used audio format
- we could force all channels to be mono, but it might
be useful to support interleaved streams
- client-side implementation requires a fair amount of
work (a helper library for writing client-side
LAAGA support would help here)
...
If I've understood right, this is very close to Paul's current AES design.
To make this a bit more concrete, let's take a practical example:
Using LAAGA for connecting Aes/Ardour (server) and TerminatorX (client):
- TerminatorX is distributed both as a standalone app and compiled
as a shared library (LAAGA client)
- Aes is started; user starts audio device configuration
- Aes shows a list of available LAAGA plugins (and internal services,
possibly Ardour itself)
- user selects TerminatorX for input and ALSA for output
- Aes loads the TerminatorX plugin (--> 'client')
- Aes issues client->open()
- TerminatorX forks/pthread_creates a new process/thread,
which is similar to the standalone TerminatorX
- TerminatorX GUI is shown to the user
- using the callbacks provided by Aes, TerminatorX
register two channels (replacing the normal stereo
soundcard output)
- Aes issues client->prepare()
- TerminatorX starts producing audio data
- Aes issues client->start()
- Aes goes into the i/o loop
- client->read() /* must be non-blocking! */
- ALSA_dev->write()
- ... and so on ...
Comments?
--
http://www.eca.cx
Audio software for Linux!
