Add session and device peak metering, and device change notifications

Cargo.toml

@@ -16,6 +16,7 @@ readme = "README.md"
 version = "0.62"
 features = ["Foundation",
             "Win32_Media_Audio",
+            "Win32_Media_Audio_Endpoints",
             "Win32_Foundation",
             "Win32_Devices_FunctionDiscovery",
             "Win32_Devices_Properties",

README.md

@@ -20,6 +20,7 @@ The following is a selection of the functionality currently available in the lib
 - Event-driven and polled buffering
 - Loopback capture
 - Notifications for volume change, device disconnect etc
+- Notifications when devices are added or removed, or when the default device changes
 - …and additional features beyond this list
 
 
@@ -36,6 +37,7 @@ The following is a selection of the functionality currently available in the lib
 | `loopback`                 | Shows how to simultaneously capture and render sound, with separate threads for capture and render.    |
 | `record`                   | Records audio from the default device, and saves the raw samples to a file.                            |
 | `devices`                  | Lists all available audio devices and displays the default devices.                                    |
-| `processes`                | Lists all available audio capture devices and lists the processes that are using them.                 |
+| `processes`                | Lists all audio devices and the processes that are using them, with the peak level of each session.    |
 | `record_application`       | Records audio from a single application, and saves the raw samples to a file.                          |
 | `aec`                      | Captures audio with Acoustic Echo Cancellation (AEC) enabled and saves the raw data to a file.         |
+| `device_notifications`     | Listens for devices being added, removed or changed, and for changes of the default device.            |

examples/device_notifications.rs

@@ -0,0 +1,34 @@
+use std::thread;
+use std::time::Duration;
+use wasapi::*;
+
+// Listen to device change notifications for one minute.
+// Plug or unplug a device, or change the default device in the
+// Windows sound settings, to see the notifications arrive.
+fn main() {
+    initialize_mta().unwrap();
+
+    let enumerator = DeviceEnumerator::new().unwrap();
+
+    let mut callbacks = DeviceEventCallbacks::new();
+
+    callbacks.set_device_added_callback(|id| println!("Device added: {id}"));
+    callbacks.set_device_removed_callback(|id| println!("Device removed: {id}"));
+    callbacks.set_device_state_callback(|id, state| println!("Device {id} is now {state}"));
+    callbacks.set_default_device_callback(|direction, role, id| match id {
+        Some(id) => println!("New default {direction} device for role {role}: {id}"),
+        None => println!("There is no longer a default {direction} device for role {role}"),
+    });
+    callbacks.set_property_value_callback(|id, key| {
+        println!("Property {:?} of device {id} changed", key.fmtid)
+    });
+
+    // The notifications are unregistered when this value is dropped,
+    // so it must be kept in scope for as long as they are needed.
+    let _registered_events = enumerator
+        .register_notification_callback(callbacks)
+        .unwrap();
+
+    println!("Listening for device changes for 60 seconds...");
+    thread::sleep(Duration::from_secs(60));
+}

examples/processes.rs

@@ -5,22 +5,35 @@ fn main() {
 
     let enumerator = DeviceEnumerator::new().unwrap();
 
-    println!("The following input devices are being used by:");
-    for device in &enumerator
-        .get_device_collection(&Direction::Capture)
-        .unwrap()
-    {
-        let dev = device.unwrap();
-        let manager = dev.get_iaudiosessionmanager().unwrap();
-        let enumerator = manager.get_audiosessionenumerator().unwrap();
+    for direction in [Direction::Capture, Direction::Render] {
+        println!("The following {direction} devices are being used by:");
+        for device in &enumerator.get_device_collection(&direction).unwrap() {
+            let dev = device.unwrap();
+            let manager = dev.get_iaudiosessionmanager().unwrap();
+            let sessions = manager.get_audiosessionenumerator().unwrap();
 
-        println!("Device: {:?}", dev.get_friendlyname().unwrap());
+            let dev_meter = dev.get_audiometerinformation().unwrap();
+            let dev_peak = dev_meter.get_peak_value().unwrap();
 
-        for i in 0..enumerator.get_count().unwrap() {
-            let control = enumerator.get_session(i).unwrap();
-            let process_id = control.get_process_id().unwrap();
+            println!(
+                "Device: {:?}, peak: {dev_peak:.3}",
+                dev.get_friendlyname().unwrap()
+            );
 
-            println!(" - In use by process: {:?}", process_id);
+            for i in 0..sessions.get_count().unwrap() {
+                let control = sessions.get_session(i).unwrap();
+                let state = control.get_state().unwrap();
+                if state != SessionState::Active {
+                    continue;
+                }
+                let process_id = control.get_process_id().unwrap();
+                let identifier = control.get_session_identifier().unwrap();
+                let meter = control.get_audiometerinformation().unwrap();
+                let peak = meter.get_peak_value().unwrap();
+
+                println!(" - In use by process: {process_id}, peak: {peak:.3}");
+                println!("   session: {identifier}");
+            }
         }
     }
 }