Re: [Jack-Devel] jack dsp load calculation

Something occurred to me while tucking into my breakfast this morning...

On 23/12/2015 15:35, Robin Gareus wrote:
> Short spikes, which are in most cases the cause for xruns, are simply
> ignored in the calculation: For them to show up [...] the spike must
> be in the last 32 jack-cycles. [...] Most control applications only
> update the value every second or so.
>

Of course!  If users are hearing xruns without them showing up in the 
DSP figure, this must be where the problem lies.  And it won't get 
solved by changing the calculation algorithm.  Removing the averaging 
would simply introduce a new set of problems without addressing the 
underlying issue (i.e. that the client is updating too infrequently).

I wondered if Jack might have any other means of notifying a client when 
an xrun occurs?  (i.e. apart from returning a load count of 100)?  Let's 
say that clients (Ardour/Mixbus or whatever) could get notified about 
xruns using a callback function.  There'd then be a simple solution.  
Instead of just querying the DSP reading once every second, clients 
could use a strategy like this (which would still work - even if only 
used once every second):-

       if ( the_client->got_notified_about_an_xrun() ) {
             //  We know that an xrun occurred since we last checked
             //  the CPU load - so do something to accommodate that.

             //  and then reset the notification flag
             reset_the_xrun_notification_flag ();
       } else {
             //  No xrun was encountered - so we can update normally...
             update_cpu_load ();
       }

Is there anything like that already available.?

John

1451122710.11331_0.ltw:2,a <567E600B.5070708 at tiscali dot co dot uk>