[pulseaudio-discuss] [PATCH 2/8] source: Fix monitor source rate changing

[Tanu Kaskinen]

On Mon, 2013-08-12 at 13:51 +0200, David Henningsson wrote:
> On 08/12/2013 01:34 PM, Tanu Kaskinen wrote:
> > On Mon, 2013-08-12 at 13:28 +0200, David Henningsson wrote:
> >> On 08/12/2013 12:18 PM, Tanu Kaskinen wrote:
> >>> On Mon, 2013-08-12 at 09:15 +0200, David Henningsson wrote:
> >>>> On 08/09/2013 08:57 AM, Tanu Kaskinen wrote:
> >>>>> Monitor sources don't have the update_rate() callback set, so their rate was
> >>>>> not being changed when changing the sink rate.
> >>>>
> >>>> For better understanding (I was a little confused first), one could add
> >>>> a sentence to the commit comment saying e g "This patch fixes this by
> >>>> changing the rate correctly, even if the update_rate callback is not set".
> >>>
> >>> Ok.
> >>>
> >>>> Can this also happen to sinks, that there might be types of sinks that
> >>>> do not have update_rate set, and might fall into the same bug?
> >>>
> >>> I don't think there are such sinks. Monitor sources are special, because
> >>> they are automatically created by the core. All other sources and sinks
> >>> are supposed to set update_rate() if they support rate switching.
> >>>
> >>
> >> So, with this patch, it looks like sources not supporting rate
> >> switching, will not set update_rate initially, and then crash in
> >> assert(monitor_of) ?
> > 
> > There's
> > 
> > -    if (!s->update_rate)
> > +    if (!s->update_rate && !s->monitor_of)
> >          return false;
> > 
> > in the beginning of the patch.
> > 
> 
> Oh, missed that. So, would it not be easier just to add an update_rate
> callback to monitor sources (that have a sink with an update_rate
> callback?), if that is our indicator that a sink/source supports
> updating rates?

I don't know if it would be easier. This patch is not complex either. I
did briefly consider adding a callback, but I thought that implementing
callbacks in the core is sort of ugly, because it adds indirection where
indirection isn't needed. That's not a strong opinion, though - I see
how it would make pa_source_update_rate() a bit easier to follow.
However, now that I try to think how to implement patch 8 in a callback,
I don't think it's possible to do cleanly. The passthrough flag is the
problem: it's not passed to the callback. For that reason I'd like to
keep this patch as it is.

-- 
Tanu