Re: Jack/USB cycle of USB output Sound device.

On Sat, March 30, 2019 13:25, Fons Adriaensen wrote:
> On Sat, Mar 30, 2019 at 11:26:24AM +0100, Thomas Brand wrote:
>
>
>> I think it's not that simple. If jack looses its backend, there's
>> nothing to connect to, no clock etc. Even if jack can take care of the
>> time where no backend is available, if a new backend is attached, it
>> might have a different SR or different buffersize.
>
> Actually I think something could be done without too much complexity.
>
>
> * When Jack detects that a backend goes away, it switches to a 'dummy'
> one with the same sample rate, buffer size, and number of channels.
> Basically this is the same as freewheeling, except that waiting for
> a timer would be inserted in between cycles.
>
> * When the backend is available again, there is a single API call
> that re-initiliases it with the existing parameters. Once this is done,
> Jack switches back.
>
>
> Apart from signalling the events (again similar to freewheeling) this
> could be transparent to clients.
>
>
Good idea, instead of shutting down, the server would just go into
freewheeling (which clients should be able to handle transparently) until
a new backend is attached.
If server operation would be separated from backend (freely attach /
dettach), this would open up new possibilities.
On a related note, I thought about jack to fall back to dummy interface
every time a normal start isn't possible. We could guarantee that jack can
always be started, and if backends can be freely swapped, this wouldn't be
a problem (just attach one later). Just thinking out loud.

Greetings
Thomas