Last active
July 26, 2024 00:05
-
-
Save jasonwhite/1df6ee4b5039358701d2 to your computer and use it in GitHub Desktop.
A simple PulseAudio test program for monitoring volume changes on the default sound sink.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
/** | |
* Author: Jason White | |
* License: Public Domain | |
* | |
* Description: | |
* This is a simple test program to hook into PulseAudio volume change | |
* notifications. It was created for the possibility of having an automatically | |
* updating volume widget in a tiling window manager status bar. | |
* | |
* Compiling: | |
* | |
* g++ $(shell pkg-config libpulse --cflags --libs) pulsetest.c -o pulsetest | |
*/ | |
#include <stdio.h> | |
#include <assert.h> | |
#include <signal.h> | |
#include <pulse/pulseaudio.h> | |
class PulseAudio | |
{ | |
private: | |
pa_mainloop* _mainloop; | |
pa_mainloop_api* _mainloop_api; | |
pa_context* _context; | |
pa_signal_event* _signal; | |
public: | |
PulseAudio() | |
: _mainloop(NULL), _mainloop_api(NULL), _context(NULL), _signal(NULL) | |
{ | |
} | |
/** | |
* Initializes state and connects to the PulseAudio server. | |
*/ | |
bool initialize() | |
{ | |
_mainloop = pa_mainloop_new(); | |
if (!_mainloop) | |
{ | |
fprintf(stderr, "pa_mainloop_new() failed.\n"); | |
return false; | |
} | |
_mainloop_api = pa_mainloop_get_api(_mainloop); | |
if (pa_signal_init(_mainloop_api) != 0) | |
{ | |
fprintf(stderr, "pa_signal_init() failed\n"); | |
return false; | |
} | |
_signal = pa_signal_new(SIGINT, exit_signal_callback, this); | |
if (!_signal) | |
{ | |
fprintf(stderr, "pa_signal_new() failed\n"); | |
return false; | |
} | |
signal(SIGPIPE, SIG_IGN); | |
_context = pa_context_new(_mainloop_api, "PulseAudio Test"); | |
if (!_context) | |
{ | |
fprintf(stderr, "pa_context_new() failed\n"); | |
return false; | |
} | |
if (pa_context_connect(_context, NULL, PA_CONTEXT_NOAUTOSPAWN, NULL) < 0) | |
{ | |
fprintf(stderr, "pa_context_connect() failed: %s\n", pa_strerror(pa_context_errno(_context))); | |
return false; | |
} | |
pa_context_set_state_callback(_context, context_state_callback, this); | |
return true; | |
} | |
/** | |
* Runs the main PulseAudio event loop. Calling quit will cause the event | |
* loop to exit. | |
*/ | |
int run() | |
{ | |
int ret = 1; | |
if (pa_mainloop_run(_mainloop, &ret) < 0) | |
{ | |
fprintf(stderr, "pa_mainloop_run() failed.\n"); | |
return ret; | |
} | |
return ret; | |
} | |
/** | |
* Exits the main loop with the specified return code. | |
*/ | |
void quit(int ret = 0) | |
{ | |
_mainloop_api->quit(_mainloop_api, ret); | |
} | |
/** | |
* Called when the PulseAudio system is to be destroyed. | |
*/ | |
void destroy() | |
{ | |
if (_context) | |
{ | |
pa_context_unref(_context); | |
_context = NULL; | |
} | |
if (_signal) | |
{ | |
pa_signal_free(_signal); | |
pa_signal_done(); | |
_signal = NULL; | |
} | |
if (_mainloop) | |
{ | |
pa_mainloop_free(_mainloop); | |
_mainloop = NULL; | |
_mainloop_api = NULL; | |
} | |
} | |
~PulseAudio() | |
{ | |
destroy(); | |
} | |
private: | |
/* | |
* Called on SIGINT. | |
*/ | |
static void exit_signal_callback(pa_mainloop_api *m, pa_signal_event *e, int sig, void *userdata) | |
{ | |
PulseAudio* pa = (PulseAudio*)userdata; | |
if (pa) pa->quit(); | |
} | |
/* | |
* Called whenever the context status changes. | |
*/ | |
static void context_state_callback(pa_context *c, void *userdata) | |
{ | |
assert(c && userdata); | |
PulseAudio* pa = (PulseAudio*)userdata; | |
switch (pa_context_get_state(c)) | |
{ | |
case PA_CONTEXT_CONNECTING: | |
case PA_CONTEXT_AUTHORIZING: | |
case PA_CONTEXT_SETTING_NAME: | |
break; | |
case PA_CONTEXT_READY: | |
fprintf(stderr, "PulseAudio connection established.\n"); | |
pa_context_get_server_info(c, server_info_callback, userdata); | |
// Subscribe to sink events from the server. This is how we get | |
// volume change notifications from the server. | |
pa_context_set_subscribe_callback(c, subscribe_callback, userdata); | |
pa_context_subscribe(c, PA_SUBSCRIPTION_MASK_SINK, NULL, NULL); | |
break; | |
case PA_CONTEXT_TERMINATED: | |
pa->quit(0); | |
fprintf(stderr, "PulseAudio connection terminated.\n"); | |
break; | |
case PA_CONTEXT_FAILED: | |
default: | |
fprintf(stderr, "Connection failure: %s\n", pa_strerror(pa_context_errno(c))); | |
pa->quit(1); | |
break; | |
} | |
} | |
/* | |
* Called when an event we subscribed to occurs. | |
*/ | |
static void subscribe_callback(pa_context *c, | |
pa_subscription_event_type_t type, uint32_t idx, void *userdata) | |
{ | |
unsigned facility = type & PA_SUBSCRIPTION_EVENT_FACILITY_MASK; | |
//type &= PA_SUBSCRIPTION_EVENT_TYPE_MASK; | |
pa_operation *op = NULL; | |
switch (facility) | |
{ | |
case PA_SUBSCRIPTION_EVENT_SINK: | |
op = pa_context_get_sink_info_by_index(c, idx, sink_info_callback, userdata); | |
break; | |
default: | |
assert(0); // Got event we aren't expecting. | |
break; | |
} | |
if (op) | |
pa_operation_unref(op); | |
} | |
/* | |
* Called when the requested sink information is ready. | |
*/ | |
static void sink_info_callback(pa_context *c, const pa_sink_info *i, | |
int eol, void *userdata) | |
{ | |
if (i) | |
{ | |
float volume = (float)pa_cvolume_avg(&(i->volume)) / (float)PA_VOLUME_NORM; | |
printf("percent volume = %.0f%%%s\n", volume * 100.0f, i->mute ? " (muted)" : ""); | |
} | |
} | |
/* | |
* Called when the requested information on the server is ready. This is | |
* used to find the default PulseAudio sink. | |
*/ | |
static void server_info_callback(pa_context *c, const pa_server_info *i, | |
void *userdata) | |
{ | |
printf("default sink name = %s\n", i->default_sink_name); | |
pa_context_get_sink_info_by_name(c, i->default_sink_name, sink_info_callback, userdata); | |
} | |
}; | |
int main(int argc, char *argv[]) | |
{ | |
PulseAudio pa = PulseAudio(); | |
if (!pa.initialize()) | |
return 0; | |
int ret = pa.run(); | |
return ret; | |
} |
@alexd2580 Indeed! Good catch. Not sure how I didn't notice that before. Should be fixed now. 👍
TOP!
First things first: Thanks a lot for this example. It makes the documentation of Pulse a lot easier to understand.
There's one thing I noticed though: Shouldn't line 199 assign the return value of pa_context_get_sink_info_by_index(c, idx, sink_info_callback, userdata);
to op
?
@soulsource Yes, I believe you're right. Good catch! I updated the gist.
(Note: I haven't used this gist in a very long time.)
They are only used once, so you're not leaking much, but you should unref the returned operations of lines 164, 169 and 232.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
There's actually a small bug in this snippet - the
userdata
pointer is notthis
, therefore attempts to cast it toPulseAudio*
in the callback functions will fail (produce invalid pointers).