[pulseaudio-discuss] [PATCH] sink, source: Rework reconfiguration logic to apply to more than rate
Arun Raghavan
arun at arunraghavan.net
Mon Oct 16 09:03:07 UTC 2017
This rejigs the update_rate() logic to encompass changes to the sample
spec as a whole, as well as passthrough status. As a result,
sinks/sources provide a reconfigure() method which allows
reconfiguration as required.
The behaviour itself is currently unchanged -- alsa-sink/-source do not
actually implement anything other than rate updates for now (nor are
they ever requested to). This can be modified in the future, to allow,
for example 24-bit output when incoming media supports it, as well as
channel count changes for passthrough sinks.
Another related change is that passthrough status is now part of
sink/source reconfiguration, and we can stop doing a suspend/unsuspend
when entering/leaving passthrough state. So that part is now divided
in two -- pa_sink_reconfigure() sets the sink in passthrough mode if
required, and pa_sink_enter_passthrough() sets up everything else
(this currently means only volumes, but could disable other processing)
for passthrough mode.
---
src/modules/alsa/alsa-sink.c | 16 ++++++----
src/modules/alsa/alsa-source.c | 14 +++++----
src/pulsecore/sink-input.c | 6 ++--
src/pulsecore/sink.c | 71 +++++++++++++++++-------------------------
src/pulsecore/sink.h | 7 ++---
src/pulsecore/source-output.c | 6 ++--
src/pulsecore/source.c | 58 ++++++++++++++++++----------------
src/pulsecore/source.h | 6 ++--
8 files changed, 90 insertions(+), 94 deletions(-)
diff --git a/src/modules/alsa/alsa-sink.c b/src/modules/alsa/alsa-sink.c
index 827a65081..96fd02aec 100644
--- a/src/modules/alsa/alsa-sink.c
+++ b/src/modules/alsa/alsa-sink.c
@@ -1596,31 +1596,35 @@ static bool sink_set_formats(pa_sink *s, pa_idxset *formats) {
return true;
}
-static int sink_update_rate_cb(pa_sink *s, uint32_t rate) {
+static int sink_reconfigure_cb(pa_sink *s, pa_sample_spec *spec, bool passthrough) {
struct userdata *u = s->userdata;
int i;
bool supported = false;
+ /* FIXME: we only update rate for now */
+
pa_assert(u);
for (i = 0; u->rates[i]; i++) {
- if (u->rates[i] == rate) {
+ if (u->rates[i] == spec->rate) {
supported = true;
break;
}
}
if (!supported) {
- pa_log_info("Sink does not support sample rate of %d Hz", rate);
+ pa_log_info("Sink does not support sample rate of %d Hz", spec->rate);
return -1;
}
if (!PA_SINK_IS_OPENED(s->state)) {
- pa_log_info("Updating rate for device %s, new rate is %d",u->device_name, rate);
- u->sink->sample_spec.rate = rate;
+ pa_log_info("Updating rate for device %s, new rate is %d", u->device_name, spec->rate);
+ u->sink->sample_spec.rate = spec->rate;
return 0;
}
+ /* Passthrough status change is handled during unsuspend */
+
return -1;
}
@@ -2357,7 +2361,7 @@ pa_sink *pa_alsa_sink_new(pa_module *m, pa_modargs *ma, const char*driver, pa_ca
else
u->sink->set_port = sink_set_port_cb;
if (u->sink->alternate_sample_rate)
- u->sink->update_rate = sink_update_rate_cb;
+ u->sink->reconfigure = sink_reconfigure_cb;
u->sink->userdata = u;
pa_sink_set_asyncmsgq(u->sink, u->thread_mq.inq);
diff --git a/src/modules/alsa/alsa-source.c b/src/modules/alsa/alsa-source.c
index 6bec188ea..3f87a4792 100644
--- a/src/modules/alsa/alsa-source.c
+++ b/src/modules/alsa/alsa-source.c
@@ -1398,28 +1398,30 @@ static void source_update_requested_latency_cb(pa_source *s) {
update_sw_params(u);
}
-static int source_update_rate_cb(pa_source *s, uint32_t rate) {
+static int source_reconfigure_cb(pa_source *s, pa_sample_spec *spec, bool passthrough) {
struct userdata *u = s->userdata;
int i;
bool supported = false;
+ /* FIXME: we only update rate for now */
+
pa_assert(u);
for (i = 0; u->rates[i]; i++) {
- if (u->rates[i] == rate) {
+ if (u->rates[i] == spec->rate) {
supported = true;
break;
}
}
if (!supported) {
- pa_log_info("Source does not support sample rate of %d Hz", rate);
+ pa_log_info("Source does not support sample rate of %d Hz", spec->rate);
return -1;
}
if (!PA_SOURCE_IS_OPENED(s->state)) {
- pa_log_info("Updating rate for device %s, new rate is %d", u->device_name, rate);
- u->source->sample_spec.rate = rate;
+ pa_log_info("Updating rate for device %s, new rate is %d", u->device_name, spec->rate);
+ u->source->sample_spec.rate = spec->rate;
return 0;
}
@@ -2041,7 +2043,7 @@ pa_source *pa_alsa_source_new(pa_module *m, pa_modargs *ma, const char*driver, p
else
u->source->set_port = source_set_port_cb;
if (u->source->alternate_sample_rate)
- u->source->update_rate = source_update_rate_cb;
+ u->source->reconfigure = source_reconfigure_cb;
u->source->userdata = u;
pa_source_set_asyncmsgq(u->source, u->thread_mq.inq);
diff --git a/src/pulsecore/sink-input.c b/src/pulsecore/sink-input.c
index d1e16ee27..05fe2c026 100644
--- a/src/pulsecore/sink-input.c
+++ b/src/pulsecore/sink-input.c
@@ -410,7 +410,7 @@ int pa_sink_input_new(
module-suspend-on-idle can resume a sink */
pa_log_info("Trying to change sample rate");
- if (pa_sink_update_rate(data->sink, data->sample_spec.rate, pa_sink_input_new_data_is_passthrough(data)) >= 0)
+ if (pa_sink_reconfigure(data->sink, &data->sample_spec, pa_sink_input_new_data_is_passthrough(data)) >= 0)
pa_log_info("Rate changed to %u Hz", data->sink->sample_spec.rate);
}
@@ -609,7 +609,7 @@ static void sink_input_set_state(pa_sink_input *i, pa_sink_input_state_t state)
!pa_sample_spec_equal(&i->sample_spec, &i->sink->sample_spec)) {
/* We were uncorked and the sink was not playing anything -- let's try
* to update the sample rate to avoid resampling */
- pa_sink_update_rate(i->sink, i->sample_spec.rate, pa_sink_input_is_passthrough(i));
+ pa_sink_reconfigure(i->sink, &i->sample_spec, pa_sink_input_is_passthrough(i));
}
pa_assert_se(pa_asyncmsgq_send(i->sink->asyncmsgq, PA_MSGOBJECT(i), PA_SINK_INPUT_MESSAGE_SET_STATE, PA_UINT_TO_PTR(state), 0, NULL) == 0);
@@ -1900,7 +1900,7 @@ int pa_sink_input_finish_move(pa_sink_input *i, pa_sink *dest, bool save) {
SINK_INPUT_MOVE_FINISH hook */
pa_log_info("Trying to change sample rate");
- if (pa_sink_update_rate(dest, i->sample_spec.rate, pa_sink_input_is_passthrough(i)) >= 0)
+ if (pa_sink_reconfigure(dest, &i->sample_spec, pa_sink_input_is_passthrough(i)) >= 0)
pa_log_info("Rate changed to %u Hz", dest->sample_spec.rate);
}
diff --git a/src/pulsecore/sink.c b/src/pulsecore/sink.c
index 94f41b927..017b95392 100644
--- a/src/pulsecore/sink.c
+++ b/src/pulsecore/sink.c
@@ -161,7 +161,7 @@ static void reset_callbacks(pa_sink *s) {
s->set_port = NULL;
s->get_formats = NULL;
s->set_formats = NULL;
- s->update_rate = NULL;
+ s->reconfigure = NULL;
}
/* Called from main context */
@@ -1411,9 +1411,9 @@ void pa_sink_render_full(pa_sink *s, size_t length, pa_memchunk *result) {
}
/* Called from main thread */
-int pa_sink_update_rate(pa_sink *s, uint32_t rate, bool passthrough) {
+int pa_sink_reconfigure(pa_sink *s, pa_sample_spec *spec, bool passthrough) {
int ret = -1;
- uint32_t desired_rate;
+ pa_sample_spec desired_spec;
uint32_t default_rate = s->default_sample_rate;
uint32_t alternate_rate = s->alternate_sample_rate;
uint32_t idx;
@@ -1422,10 +1422,12 @@ int pa_sink_update_rate(pa_sink *s, uint32_t rate, bool passthrough) {
bool alternate_rate_is_usable = false;
bool avoid_resampling = s->core->avoid_resampling;
- if (rate == s->sample_spec.rate)
+ /* We currently only try to reconfigure the sample rate */
+
+ if (pa_sample_spec_equal(spec, &s->sample_spec))
return 0;
- if (!s->update_rate)
+ if (!s->reconfigure)
return -1;
if (PA_UNLIKELY(default_rate == alternate_rate && !passthrough && !avoid_resampling)) {
@@ -1446,52 +1448,54 @@ int pa_sink_update_rate(pa_sink *s, uint32_t rate, bool passthrough) {
}
}
- if (PA_UNLIKELY(!pa_sample_rate_valid(rate)))
+ if (PA_UNLIKELY(!pa_sample_spec_valid(spec)))
return -1;
+ desired_spec = s->sample_spec;
+
if (passthrough) {
/* We have to try to use the sink input rate */
- desired_rate = rate;
+ desired_spec.rate = spec->rate;
- } else if (avoid_resampling && (rate >= default_rate || rate >= alternate_rate)) {
+ } else if (avoid_resampling && (spec->rate >= default_rate || spec->rate >= alternate_rate)) {
/* We just try to set the sink input's sample rate if it's not too low */
- desired_rate = rate;
+ desired_spec.rate = spec->rate;
- } else if (default_rate == rate || alternate_rate == rate) {
+ } else if (default_rate == spec->rate || alternate_rate == spec->rate) {
/* We can directly try to use this rate */
- desired_rate = rate;
+ desired_spec.rate = spec->rate;
} else {
/* See if we can pick a rate that results in less resampling effort */
- if (default_rate % 11025 == 0 && rate % 11025 == 0)
+ if (default_rate % 11025 == 0 && spec->rate % 11025 == 0)
default_rate_is_usable = true;
- if (default_rate % 4000 == 0 && rate % 4000 == 0)
+ if (default_rate % 4000 == 0 && spec->rate % 4000 == 0)
default_rate_is_usable = true;
- if (alternate_rate && alternate_rate % 11025 == 0 && rate % 11025 == 0)
+ if (alternate_rate && alternate_rate % 11025 == 0 && spec->rate % 11025 == 0)
alternate_rate_is_usable = true;
- if (alternate_rate && alternate_rate % 4000 == 0 && rate % 4000 == 0)
+ if (alternate_rate && alternate_rate % 4000 == 0 && spec->rate % 4000 == 0)
alternate_rate_is_usable = true;
if (alternate_rate_is_usable && !default_rate_is_usable)
- desired_rate = alternate_rate;
+ desired_spec.rate = alternate_rate;
else
- desired_rate = default_rate;
+ desired_spec.rate = default_rate;
}
- if (desired_rate == s->sample_spec.rate)
+ if (pa_sample_spec_equal(&desired_spec, &s->sample_spec) && passthrough == pa_sink_is_passthrough(s))
return -1;
if (!passthrough && pa_sink_used_by(s) > 0)
return -1;
- pa_log_debug("Suspending sink %s due to changing the sample rate.", s->name);
+ pa_log_debug("Suspending sink %s due to changing format.", s->name);
pa_sink_suspend(s, true, PA_SUSPEND_INTERNAL);
- if (s->update_rate(s, desired_rate) >= 0) {
+ if (s->reconfigure(s, &desired_spec, passthrough) >= 0) {
/* update monitor source as well */
if (s->monitor_source && !passthrough)
- pa_source_update_rate(s->monitor_source, desired_rate, false);
- pa_log_info("Changed sampling rate successfully");
+ pa_source_reconfigure(s->monitor_source, &desired_spec, false);
+ pa_log_info("Changed format successfully");
PA_IDXSET_FOREACH(i, s->inputs, idx) {
if (i->state == PA_SINK_INPUT_CORKED)
@@ -1626,10 +1630,9 @@ bool pa_sink_is_passthrough(pa_sink *s) {
void pa_sink_enter_passthrough(pa_sink *s) {
pa_cvolume volume;
- if (s->is_passthrough_set) {
- pa_log_debug("Sink %s is already in passthrough mode, nothing to do", s->name);
- return;
- }
+ /* The sink implementation is reconfigured for passthrough in
+ * pa_sink_reconfigure(). This function sets the PA core objects to
+ * passthrough mode. */
/* disable the monitor in passthrough mode */
if (s->monitor_source) {
@@ -1645,21 +1648,10 @@ void pa_sink_enter_passthrough(pa_sink *s) {
pa_sink_set_volume(s, &volume, true, false);
pa_log_debug("Suspending/Restarting sink %s to enter passthrough mode", s->name);
-
- /* force sink to be resumed in passthrough mode */
- pa_sink_suspend(s, true, PA_SUSPEND_INTERNAL);
- s->is_passthrough_set = true;
- pa_sink_suspend(s, false, PA_SUSPEND_INTERNAL);
}
/* Called from main context */
void pa_sink_leave_passthrough(pa_sink *s) {
-
- if (!s->is_passthrough_set) {
- pa_log_debug("Sink %s is not in passthrough mode, nothing to do", s->name);
- return;
- }
-
/* Unsuspend monitor */
if (s->monitor_source) {
pa_log_debug("Resuming monitor source %s, because the sink is leaving the passthrough mode.", s->monitor_source->name);
@@ -1672,11 +1664,6 @@ void pa_sink_leave_passthrough(pa_sink *s) {
pa_cvolume_init(&s->saved_volume);
s->saved_save_volume = false;
- /* force sink to be resumed in non-passthrough mode */
- pa_sink_suspend(s, true, PA_SUSPEND_INTERNAL);
- s->is_passthrough_set = false;
- pa_sink_suspend(s, false, PA_SUSPEND_INTERNAL);
-
}
/* Called from main context. */
diff --git a/src/pulsecore/sink.h b/src/pulsecore/sink.h
index 7deafdd85..cae5e517b 100644
--- a/src/pulsecore/sink.h
+++ b/src/pulsecore/sink.h
@@ -108,7 +108,6 @@ struct pa_sink {
/* Saved volume state while we're in passthrough mode */
pa_cvolume saved_volume;
bool saved_save_volume:1;
- bool is_passthrough_set:1;
pa_asyncmsgq *asyncmsgq;
@@ -245,9 +244,9 @@ struct pa_sink {
* set). Makes a copy of the formats passed in. */
bool (*set_formats)(pa_sink *s, pa_idxset *formats); /* may be NULL */
- /* Called whenever the sampling frequency shall be changed. Called from
+ /* Called whenever device parameters need to be changed. Called from
* main thread. */
- int (*update_rate)(pa_sink *s, uint32_t rate);
+ int (*reconfigure)(pa_sink *s, pa_sample_spec *spec, bool passthrough);
/* Contains copies of the above data so that the real-time worker
* thread can work without access locking */
@@ -423,7 +422,7 @@ unsigned pa_device_init_priority(pa_proplist *p);
/**** May be called by everyone, from main context */
-int pa_sink_update_rate(pa_sink *s, uint32_t rate, bool passthrough);
+int pa_sink_reconfigure(pa_sink *s, pa_sample_spec *spec, bool passthrough);
void pa_sink_set_port_latency_offset(pa_sink *s, int64_t offset);
/* The returned value is supposed to be in the time domain of the sound card! */
diff --git a/src/pulsecore/source-output.c b/src/pulsecore/source-output.c
index 687b2b567..f8a421aa8 100644
--- a/src/pulsecore/source-output.c
+++ b/src/pulsecore/source-output.c
@@ -356,7 +356,7 @@ int pa_source_output_new(
module-suspend-on-idle can resume a source */
pa_log_info("Trying to change sample rate");
- if (pa_source_update_rate(data->source, data->sample_spec.rate, pa_source_output_new_data_is_passthrough(data)) >= 0)
+ if (pa_source_reconfigure(data->source, &data->sample_spec, pa_source_output_new_data_is_passthrough(data)) >= 0)
pa_log_info("Rate changed to %u Hz", data->source->sample_spec.rate);
}
@@ -529,7 +529,7 @@ static void source_output_set_state(pa_source_output *o, pa_source_output_state_
!pa_sample_spec_equal(&o->sample_spec, &o->source->sample_spec)) {
/* We were uncorked and the source was not playing anything -- let's try
* to update the sample rate to avoid resampling */
- pa_source_update_rate(o->source, o->sample_spec.rate, pa_source_output_is_passthrough(o));
+ pa_source_reconfigure(o->source, &o->sample_spec, pa_source_output_is_passthrough(o));
}
pa_assert_se(pa_asyncmsgq_send(o->source->asyncmsgq, PA_MSGOBJECT(o), PA_SOURCE_OUTPUT_MESSAGE_SET_STATE, PA_UINT_TO_PTR(state), 0, NULL) == 0);
@@ -1523,7 +1523,7 @@ int pa_source_output_finish_move(pa_source_output *o, pa_source *dest, bool save
SOURCE_OUTPUT_MOVE_FINISH hook */
pa_log_info("Trying to change sample rate");
- if (pa_source_update_rate(dest, o->sample_spec.rate, pa_source_output_is_passthrough(o)) >= 0)
+ if (pa_source_reconfigure(dest, &o->sample_spec, pa_source_output_is_passthrough(o)) >= 0)
pa_log_info("Rate changed to %u Hz", dest->sample_spec.rate);
}
diff --git a/src/pulsecore/source.c b/src/pulsecore/source.c
index e0d32af4e..d579c3574 100644
--- a/src/pulsecore/source.c
+++ b/src/pulsecore/source.c
@@ -150,7 +150,7 @@ static void reset_callbacks(pa_source *s) {
s->update_requested_latency = NULL;
s->set_port = NULL;
s->get_formats = NULL;
- s->update_rate = NULL;
+ s->reconfigure = NULL;
}
/* Called from main context */
@@ -981,19 +981,21 @@ void pa_source_post_direct(pa_source*s, pa_source_output *o, const pa_memchunk *
}
/* Called from main thread */
-int pa_source_update_rate(pa_source *s, uint32_t rate, bool passthrough) {
+int pa_source_reconfigure(pa_source *s, pa_sample_spec *spec, bool passthrough) {
int ret;
- uint32_t desired_rate;
+ pa_sample_spec desired_spec;
uint32_t default_rate = s->default_sample_rate;
uint32_t alternate_rate = s->alternate_sample_rate;
bool default_rate_is_usable = false;
bool alternate_rate_is_usable = false;
bool avoid_resampling = s->core->avoid_resampling;
- if (rate == s->sample_spec.rate)
+ /* We currently only try to reconfigure the sample rate */
+
+ if (pa_sample_spec_equal(spec, &s->sample_spec))
return 0;
- if (!s->update_rate && !s->monitor_of)
+ if (!s->reconfigure && !s->monitor_of)
return -1;
if (PA_UNLIKELY(default_rate == alternate_rate && !passthrough && !avoid_resampling)) {
@@ -1014,39 +1016,41 @@ int pa_source_update_rate(pa_source *s, uint32_t rate, bool passthrough) {
}
}
- if (PA_UNLIKELY(!pa_sample_rate_valid(rate)))
+ if (PA_UNLIKELY(!pa_sample_spec_valid(spec)))
return -1;
+ desired_spec = s->sample_spec;
+
if (passthrough) {
/* We have to try to use the source output rate */
- desired_rate = rate;
+ desired_spec.rate = spec->rate;
- } else if (avoid_resampling && (rate >= default_rate || rate >= alternate_rate)) {
+ } else if (avoid_resampling && (spec->rate >= default_rate || spec->rate >= alternate_rate)) {
/* We just try to set the source output's sample rate if it's not too low */
- desired_rate = rate;
+ desired_spec.rate = spec->rate;
- } else if (default_rate == rate || alternate_rate == rate) {
+ } else if (default_rate == spec->rate || alternate_rate == spec->rate) {
/* We can directly try to use this rate */
- desired_rate = rate;
+ desired_spec.rate = spec->rate;
} else {
/* See if we can pick a rate that results in less resampling effort */
- if (default_rate % 11025 == 0 && rate % 11025 == 0)
+ if (default_rate % 11025 == 0 && spec->rate % 11025 == 0)
default_rate_is_usable = true;
- if (default_rate % 4000 == 0 && rate % 4000 == 0)
+ if (default_rate % 4000 == 0 && spec->rate % 4000 == 0)
default_rate_is_usable = true;
- if (alternate_rate && alternate_rate % 11025 == 0 && rate % 11025 == 0)
+ if (alternate_rate && alternate_rate % 11025 == 0 && spec->rate % 11025 == 0)
alternate_rate_is_usable = true;
- if (alternate_rate && alternate_rate % 4000 == 0 && rate % 4000 == 0)
+ if (alternate_rate && alternate_rate % 4000 == 0 && spec->rate % 4000 == 0)
alternate_rate_is_usable = true;
if (alternate_rate_is_usable && !default_rate_is_usable)
- desired_rate = alternate_rate;
+ desired_spec.rate = alternate_rate;
else
- desired_rate = default_rate;
+ desired_spec.rate = default_rate;
}
- if (desired_rate == s->sample_spec.rate)
+ if (pa_sample_spec_equal(&desired_spec, &s->sample_spec) && passthrough == pa_source_is_passthrough(s))
return -1;
if (!passthrough && pa_source_used_by(s) > 0)
@@ -1055,8 +1059,8 @@ int pa_source_update_rate(pa_source *s, uint32_t rate, bool passthrough) {
pa_log_debug("Suspending source %s due to changing the sample rate.", s->name);
pa_source_suspend(s, true, PA_SUSPEND_INTERNAL);
- if (s->update_rate)
- ret = s->update_rate(s, desired_rate);
+ if (s->reconfigure)
+ ret = s->reconfigure(s, &desired_spec, passthrough);
else {
/* This is a monitor source. */
@@ -1064,23 +1068,23 @@ int pa_source_update_rate(pa_source *s, uint32_t rate, bool passthrough) {
* have no idea whether the behaviour with passthrough streams is
* sensible. */
if (!passthrough) {
- uint32_t old_rate = s->sample_spec.rate;
+ pa_sample_spec old_spec = s->sample_spec;
- s->sample_spec.rate = desired_rate;
- ret = pa_sink_update_rate(s->monitor_of, desired_rate, false);
+ s->sample_spec = desired_spec;
+ ret = pa_sink_reconfigure(s->monitor_of, &desired_spec, false);
if (ret < 0) {
/* Changing the sink rate failed, roll back the old rate for
* the monitor source. Why did we set the source rate before
- * calling pa_sink_update_rate(), you may ask. The reason is
- * that pa_sink_update_rate() tries to update the monitor
+ * calling pa_sink_reconfigure(), you may ask. The reason is
+ * that pa_sink_reconfigure() tries to update the monitor
* source rate, but we are already in the process of updating
* the monitor source rate, so there's a risk of entering an
* infinite loop. Setting the source rate before calling
- * pa_sink_update_rate() makes the rate == s->sample_spec.rate
+ * pa_sink_reconfigure() makes the rate == s->sample_spec.rate
* check in the beginning of this function return early, so we
* avoid looping. */
- s->sample_spec.rate = old_rate;
+ s->sample_spec = old_spec;
}
} else
ret = -1;
diff --git a/src/pulsecore/source.h b/src/pulsecore/source.h
index 1e33cde2d..7fb4a79ea 100644
--- a/src/pulsecore/source.h
+++ b/src/pulsecore/source.h
@@ -202,9 +202,9 @@ struct pa_source {
* in descending order of preference. */
pa_idxset* (*get_formats)(pa_source *s); /* ditto */
- /* Called whenever the sampling frequency shall be changed. Called from
+ /* Called whenever device parameters need to be changed. Called from
* main thread. */
- int (*update_rate)(pa_source *s, uint32_t rate);
+ int (*reconfigure)(pa_source *s, pa_sample_spec *spec, bool passthrough);
/* Contains copies of the above data so that the real-time worker
* thread can work without access locking */
@@ -396,7 +396,7 @@ bool pa_source_update_proplist(pa_source *s, pa_update_mode_t mode, pa_proplist
int pa_source_set_port(pa_source *s, const char *name, bool save);
void pa_source_set_mixer_dirty(pa_source *s, bool is_dirty);
-int pa_source_update_rate(pa_source *s, uint32_t rate, bool passthrough);
+int pa_source_reconfigure(pa_source *s, pa_sample_spec *spec, bool passthrough);
unsigned pa_source_linked_by(pa_source *s); /* Number of connected streams */
unsigned pa_source_used_by(pa_source *s); /* Number of connected streams that are not corked */
--
2.13.6
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