[pulseaudio-discuss] [PATCH] pacat: make pacat respond to cork/uncork events

Lu Guanqun guanqun.lu at intel.com
Tue Aug 23 01:30:45 PDT 2011

Hi Col,

On Tue, Aug 23, 2011 at 04:22:48PM +0800, Colin Guthrie wrote:
> 'Twas brillig, and Lu Guanqun at 23/08/11 07:18 did gyre and gimble:
> > Pacat remembers the number of cork requests, and then cork/uncork the stream
> > accordingly.
> > 
> > With this change, it makes below test script work correctly:
> > 
> > 	pacat -p --property=media.role="music" <long-sound> &
> > 	sleep 2
> > 	pacat -p --property=media.role="phone" <short-sound>
> > 	wait
> Interesting, this is likely good as a test bed/example.

Thanks. I was trying module-cork-music-on-phone and came up with this
little script. :)

> That said, I'm not sure we should be sending the operations every time.
> Perhaps we should only send a cork req when the count moves form 0->1
> and an uncork when the count moves from 1->0?

At my first attempt, I'm only doing something like below:

diff --git a/src/utils/pacat.c b/src/utils/pacat.c
index f687402..41817ff 100644
--- a/src/utils/pacat.c
+++ b/src/utils/pacat.c
@@ -408,6 +410,12 @@ static void stream_event_callback(pa_stream *s, const char *name, pa_proplist *p
     t = pa_proplist_to_string_sep(pl, ", ");
     pa_log("Got event '%s', properties '%s'", name, t);
+    if (pa_streq(name, PA_STREAM_EVENT_REQUEST_CORK))
+        pa_operation_unref(pa_stream_cork(s, 1, NULL, NULL));
+    else if (pa_streq(name, PA_STREAM_EVENT_REQUEST_UNCORK))
+        pa_operation_unref(pa_stream_cork(s, 0, NULL, NULL));
But I read the mailing list and once someone said it's better for client
to remember how many cork requests it receives and only uncork it when
it reaches zero. That's why I changed to the current style.

Do you think my original code is better for this case?

> We may at some point have to change the semantics at the server side to
> deal with the start_corked issue, and thus this is likely more robust in
> those circumstances.

It should. However for 'pacat', it doesn't set START_CORKED flag, so I'm
afraid there's no such problem for 'pacat'.


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