Merge pull request #862 from RustAudio/filter-out-null

Cpal has (correctly) started listing the null device in 0.17. This messes up our Sink's fallback strategy since it can now land on the null device (which happily eats all samples without producing any sound.) This fixes that by filtering it out.

Our microphone input has a different API, it does not have fallback. We provide a method to list all input devices which was now including null, a possible footgun if users try to implement fallback themselves. We've taken that out for now.

Author: yara-blue

src/microphone.rs

@@ -166,13 +166,19 @@ impl fmt::Display for Input {
 }
 
 /// Returns a list of available input devices on the system.
+///
+/// Note: this hides the 'null' device which generates zeros.
 pub fn available_inputs() -> Result<Vec<Input>, ListError> {
-    let host = cpal::default_host();
-    let devices = host
+    Ok(cpal::default_host()
         .input_devices()
         .map_err(ListError)?
-        .map(|dev| Input { inner: dev });
-    Ok(devices.collect())
+        .filter(|dev| {
+            dev.description()
+                .map(|descr| descr.driver().is_none_or(|driver| driver != "null"))
+                .unwrap_or(false)
+        })
+        .map(|dev| Input { inner: dev })
+        .collect::<Vec<_>>())
 }
 
 /// A microphone input stream that can be used as `Source`.

src/stream.rs

@@ -234,7 +234,7 @@ impl DeviceSinkBuilder {
         Self::from_default_device()
             .and_then(|x| x.open_stream())
             .or_else(|original_err| {
-                let mut devices = match cpal::default_host().output_devices() {
+                let devices = match cpal::default_host().output_devices() {
                     Ok(devices) => devices,
                     Err(err) => {
                         #[cfg(feature = "tracing")]
@@ -245,6 +245,11 @@ impl DeviceSinkBuilder {
                     }
                 };
                 devices
+                    .filter(|dev| {
+                        dev.description()
+                            .map(|desc| desc.driver().is_some_and(|driver| driver != "null"))
+                            .unwrap_or(false)
+                    })
                     .find_map(|d| {
                         Self::from_device(d)
                             .and_then(|x| x.open_sink_or_fallback())