[pulseaudio-discuss] Pause a audio stream

Thu Dec 19 20:18:59 PST 2013

>
> Hi ,
>
> I am trying to add a new function "pa_context_set_sink_input_paused" to
the pulseaudio introspect.c file. I was able to able and successfully
compile pulseaudio too..
>
> gcc pa_listclients_pause.c -o pa_listclients_pause -L
/home/sathish/Desktop/pulseaudio-4.0/build/src/.libs/ -lpulse
>
> /tmp/ccueP47b.o: In function `pa_get_devicelist':
>
> pa_listclients_pause.c.text+0x6cb): undefined reference to
`pa_context_set_sink_input_paused'
>
> collect2: error: ld returned 1 exit status
>
> But when I try to run a program using this new function, it returns me
"undefined reference".
>
> I tried to run the nm command and check whether the new function is
present in libpulse.so
>
> The function returns me it has found it..
>
> nm -A *.so | grep "pa_context_set_sink_input_paused"
>
> libpulse.so:0001d4a0 t pa_context_set_sink_input_paused
>
> I am not able to comprehend what is happening. Can you help me with this
??
>
> Thanks,
>
> Sathish
>
>
>
> From: Sathishkumar Sivagurunathan
> Sent: Thursday, December 19, 2013 2:24 PM
> To: 'sathishkumar sivagurunathan'
> Subject: RE: Re: [pulseaudio-discuss] Pause a audio stream
>
>
>
> Hi Tanu,
>
>
>
> Thanks for the reply and advice,
>
>
>
>        1) My current aim is just short term. Hence I would just like to
have pause implemented through the introspect.h as a first step.
>
>
>
>        In accordance with my previous mail, I had made the changes to the
necessary files and compiled using the "make". But somehow when I run my c
program which calls the function “pa_context_request_sink_input_cork()”, it
seems to not pick up the new function defined in introspect.c. It returns a
undefined reference error..
>
>
>
>        The command I used for compiling the program I am using to call
the cork functionality points lpulse library.
>
>
>
>        Is there something other than "make" I should be looking at ??
>
>
>
>        The compilation of PulseAudio with the changes was successful
without any errors..
>
>
>
>        2) But if you can help me understand this client - server concept,
I will try to take as the next step. My doubts in this are pretty
elementary but it will help me a lot if you can clear them.
>
>
>
>        a) "Murphy is an external policy manager, but it will also have a
dedicated module in PulseAudio."
>
>
>
>             The one I am working on is similar to Murphy. When you say,
we will have a dedicated module, should this module be like the other
modules like "module-role-cork" ??
>
>
>
>        b) "Instead, the Murphy module in PulseAudio will be a client to
Murphy, using Murphy's APIs, so the client-server relationship is the other
way around than in your setup."
>
>
>
>             Now, Murphy module in PulseAudio is client, Murphy is the
server. How will the murphy api's in the client will be called. Will it be
through the "load-module" functionality currently available with pactl,
loaded by pulseaudio at daemon start up or like a C function call..
>
>
>
>           In short, it would be great if you can help understand how the
communication between these three thing takes place ??
>
>
>
>                                   Murphy --> Murphy module in PulseAudio
() --> PulseAudio..
>
>
>
> Thanks,
>
> Sathish
>
>
>
> From: sathishkumar sivagurunathan [mailto:sathish1000 at gmail.com]
> Sent: Thursday, December 19, 2013 12:19 PM
> To: Sathishkumar Sivagurunathan
> Subject: Fwd: Re: [pulseaudio-discuss] Pause a audio stream
>
>
>
> ---------- Forwarded message ----------
> From: "Tanu Kaskinen" <tanu.kaskinen at linux.intel.com>
> Date: Dec 16, 2013 4:18 PM
> Subject: Re: [pulseaudio-discuss] Pause a audio stream
> To: "sathishkumar sivagurunathan" <sathish1000 at gmail.com>
> Cc: <pulseaudio-discuss at lists.freedesktop.org>
>
> On Sat, 2013-12-14 at 14:25 +0530, sathishkumar sivagurunathan wrote:
> > Thanks Tanu for the reply,
> >
> > I have been trying to some simple analysis for the past on  this
question
> > below I raised before you last time..
> >
> > 1) I have a routing policy manager which would like to cork/pause a
> >  stream. No priority is involved in this usecase. Is it this possible
with
> >  Pulse Audio.
> >
> > Only the application that created the stream can cork it. External
> > policy managers can't do that. This may change in the future, but don't
> > count on that. If you want to implement a policy for corking streams,
> > you have to do that in a PulseAudio module.
> >
> > Tanu, I understand that it is possible only by the application to cork
the
> > stream. I really tried using the "module-role-cork" module.
> > But I couldn't fit it into my need for having called from my policy
> > manager..
> >
> > Hence, I was trying to go through the code if something different can be
> > done. I had presented my analysis to you. Glad to hear your comments on
> > it..
> >
> > My idea is (though my analysis might not be perfect) :-
> >
> > 1) I looked at the available C API's that are available in
Instrospect.c.
> > It houses the C API's to be called for muting, changing volume etc.
> > Is it possible to add a function to this Introspect.c for pause
> > functionality.
> >
> > 2) I also saw that C API's in Introspect.c like called functions in
> > protocol-native.c to execute the functionality.
> >     Example:- *pa_context_set_sink_mute_by_index* function in
Introspect.c
> > calls *command_set_mute *in protocol-native.c.
> >
> > 3) Hence is it possible to write a new function for pause say "
> > *pa_context_set_sink_input_pause*" in Introspect.c and call "
> > *command_set_pause*" in protocol-native.c.
>
> About the function naming: "pause" isn't a good term, because we already
> use the term "cork" that means the same thing. Also,
> "set_sink_input_cork" isn't good, because you only send a request to the
> client, you don't set the cork state directly. Perhaps
> "pa_context_request_sink_input_cork()" would be good?
>
> > 4) This new function "*command_set_pause*" in protocol-native.c calls
> > into "*pa_sink_input_send_event"
> > *in sink-input.c and henceforth the event is relayed to the application
for
> > pausing.
> >
> > 5) Indeed I am just trying to use the same chain of command followed by
"
> > *module-role-cork*" module to relay command which is
> >    * module-role-cork* -> *pa_sink_input_send_event*  in sink-input.c ->
> > *sink_input_send_event_cb* in protocol-native.c -> Application --> which
> > instructs to pause.
> >
> > 6) I am just to come from the Introspect.c side..
> >    *pa_context_set_sink_input_pause *in Introspect.c ->
 *command_set_pause
> > *in protocol-native.c -> *pa_sink_input_send_event*  in sink-input.c ->
> > *sink_input_send_event_cb* in protocol-native.c -> Application --> which
> > instructs to pause.
> >
> > My questions are:-
> >
> > Is this feasible.. I am asking this because i trying to connect as a
client
> > and do it. And you had mentioned that client would be allowed to do
such a
> > thing..
>
> It's feasible. I don't know if it's a good idea, though. I think it's
> asking for trouble to do audio policy enforcement relying only on an
> external component, because there will always be able things that you
> can't control from outside the server, things like the initial routing
> and volume of a new stream.
>
> I'm working myself on bringing Murphy support to PulseAudio. Murphy is
> an external policy manager, but it will also have a dedicated module in
> PulseAudio. I will need to handle corking policy too, but I don't know
> yet the details about how that will be handled (I've been working on
> routing policy so far). I'm pretty sure it will not be handled via the
> introspect.h API, however. Murphy won't use PulseAudio's client API, as
> far as I know. Instead, the Murphy module in PulseAudio will be a client
> to Murphy, using Murphy's APIs, so the client-server relationship is the
> other way around than in your setup.
>
> If you send patches for adding pa_context_request_sink_input_cork()
> anyway, I won't reject those. While I think you're likely to regret the
> decision to use an external policy manager that only uses the client
> API, I don't have proof that it won't be good enough for your purposes,
> so I shouldn't block this feature.
>
> --
> Tanu
>
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