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

[Lee Revell]

On Mon, 2005-12-12 at 11:47 -0500, Paul Davis wrote:
> ( 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.
> 

If we can agree on the goals below the next step is to determine which
of these don't already Just Work and of the remaining items, which will
need to be solved at the application level (IOW specified in that
desktop environment's requirements for a correct audio app) and which
can be solved at lower level.  For example, in order to control
application volumes independently, in the event that the hardware does
not support it do we require each app to implement a software volume
control?  Or can it be solved at the ALSA level without requiring an
intermediate buffer or extra copy?

Also we need to select a baseline system to determine how many of these
items Just Work already.  Personally I would recommend a recent Ubuntu
distro with the latest Gnome release.

Another question, where do we draw the line between things that should
Just Work and which should be possible but require configuration by the
user.  For example "use multiple soundcards as a single logical device"
is tricky - do you think it's realistic to expect an idiot proof
interface for this?

I'd also like to see the OSS API go away as it makes meeting the goals
below much easier.

> 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
> 	            
> 
> 
>