Re: [Jack-Devel] transport rolling + new slow-sync client

On Fri, Jun 10, 2011 at 05:49:57PM +0300, Dan Muresan wrote:


> I was wondering what happens if the transport is already Rolling, and
> a new slow-start client activates itself? Does Jack transition from
> Rolling to Starting and wait for the new client to complete syncing? I
> don't see that transition in the diagram -- and without it I don't
> understand how a slow-start client could reliably synchronize with an
> already-rolling transport...

I don't think you can expect that to work.

If Jack would wait for the new client that would probably be more
disruptive than anything else.

The whole slow-start system is IMHO fundamentally flawed, because
checking for readyness is done only when the transport is supposed
to have already started. This makes it impossible to start on cue,
unless you are lucky and all clients involved happen to be ready.

To make it really work would require:

1. Clients capable to catch up and sync by themselves if the transport
   starts when they are not ready, probably outputting silence until
   they have synced (that would also solve your case).

2. Clients that, when transport is stopped and locates to a new
   position, get ready to start without delay at that position
   instead of waiting for a transport start (many probably do
   this already, but it's not required and can't be checked),

3. A way for clients to indicate their readyness to start without
   delay _while transport is stopped_.


This means you have a 2-element state:

STOPPED  or  ROLLING
SYNCED   or  LOCATING

and  *all four*  combinations are possible and are reported.
The combination STOPPED + LOCATING (i.e. not ready to start
while stopped) doesn't exist in the current design.


Ciao,

-- 
FA

1307719284.30993_0.ltw:2,a <20110610152100.GE19115 at linuxaudio dot org>