[linux-audio-user] Making Audio on Linux Just Work: (1) defining the goals

[Paul Davis]

( LAU folk: this is an initial outline of an email I want to dispatch to
  the desktop-architects list in the very near future. Your comments
  are eagerly sought. Note that this section specifically seeks to
  avoid any discussion of implementations or specific approachs. I   
  would like to fully flesh out the list of tasks ASAP )

			Making Sound Just Work
		       ------------------------

One of the "second tier" of requirements mentioned several times at
the OSDL Portland Linux Desktop Architects workshop was "making audio
on Linux just work". Many people find it easy to leave this
requirement lying around in various lists of goals and requirements,
but before we can make any progress on defining a plan to implement
the goal, we first need to define it rather more precisely.

DEFINING THE GOAL
=================

The list below is a set of tasks that a user could reasonably expect
to perform on a computer running Linux that has access to zero, one
or more audio interfaces. 

The desired task should either work, or produce a sensible and
comprehensible error message explaining why it failed. For example,
attempting to control input gain on a device that has no hardware
mixer should explain that the device has no controls for input gain.

 PLAYBACK
         
          - play a compressed audio file 
	        * user driven (e.g. play(1))
		* app driven (e.g. {kde,gnome_play}_audiofile())
	  - play a PCM encoded audio file (specifics as above)
	  - hear system sounds
	  - VOIP
	  - game audio
	  - music composition
	  - music editing
	  - video post production

 RECORDING
      
          - record from hardware inputs
	      * use default audio interface
	      * use other audio interface
	      * specify which h/w input to use
	      * control input gain
	  - record from other application(s)
	  - record from live (network-delivered) compressed audio
          	  streams


 MIXING

	  - control h/w mixer device (if any)

	       * allow use of a generic app for this
	       * NOTE to non-audio-focused readers: the h/w mixer
	         is part of the audio interface that is used
		 to control signal levels, input selection
		 for recording, and other h/w specific features.
		 Some pro-audio interfaces do not have a h/w mixer,
		 most consumer ones do. It has almost nothing
		 to do with "hardware mixing" which describes
		 the ability of the h/w to mix together multiple
		 software-delivered audio data streams.

          - multiple applications using soundcard simultaneously
	  - control application volumes independently
	  - provide necessary apps for controlling specialized
	       hardware (e.g. RME HDSP, ice1712, ice1724, liveFX)

 ROUTING

          - route audio to specific h/w among several installed devices
	  - route audio between applications
	  - route audio across network
	  
 MULTIUSER

          - which of the above should work in a multi-user scenario?

 MISC
      
          - use multiple soundcards as a single logical device