[Spice-devel] RFC - Make sound receiving and deconding independent from the gtk widget

[Mario Lombardo]

Hi,

I just trying to implement sound into my SDL client. This client uses 
the spice glib but it does not use the gtk library (as gtk is horrible 
slow on OSX).

Here I noticed a design break in spice. Every channel is more or less 
implemented in two parts:

1.) Spice Protocol decoding is implemented in the spice-glib
2.) Spice Data presentation and grabbing is implemented in spice-gtk

However if I only want need the spice-glib it works like a charm until I 
try to implement sound. Sound decoding is impossible because the 
function spice_audio_new in spice-audio.c does not provide a valid 
pointer if there is no backend. But why is the backend for sound 
implemented (partially) and depending on a sound presentation library in 
the glib?

Here is a draft that works for me when I want to use sound in my client 
even if the gtk library does not support sound:

/***** spice-audio.c *****/
[...]
SpiceAudio *spice_audio_new(SpiceSession *session, GMainContext 
*context,
                             const char *name)
{
     SpiceAudio *self = NULL;

     if (context == NULL)
         context = g_main_context_default();
     if (name == NULL)
         name = g_get_application_name();

#if defined (WITH_PULSE)
     /* implement the pulse backend for later use in the gtk library */
     self = SPICE_AUDIO(spice_pulse_new(session, context, name));
#elif defined (WITH_GSTAUDIO)
     /* implement the gstreamer backend for later use in the gtk library 
*/
     self = SPICE_AUDIO(spice_gstaudio_new(session, context, name));
#else
     /* implement no specific backend to enable the glib the funtionality 
that
      * including <channel-playback.h> makes sense */
     self = SPICE_AUDIO(g_object_new(SPICE_TYPE_FAKE_AUDIO, NULL));
#endif
     if (!self)
         return NULL;

     spice_g_signal_connect_object(session, "notify::enable-audio", 
G_CALLBACK(session_enable_audio), self, 0);
     spice_g_signal_connect_object(session, "channel-new", 
G_CALLBACK(channel_new), self, 0);
     update_audio_channels(self, session);

     return self;
}
[...]

SPICE_TYPE_FAKE_AUDIO is just a dummy object class to have a valid 
object 'self'.

Is it possible to have an upstream version of spice that does not depend 
on gstreamer or pulse but that is able to register callbacks for sound 
playback?

Thank you!

Mario