adds docs for BufferSize and fixes buffersize bugs in emscripten and alsa

src/host/alsa/mod.rs

@@ -905,13 +905,6 @@ fn set_hw_params_from_format<'a>(
         BufferSize::Default => (),
     }
 
-    // If this isn't set manually a overlarge buffer may be used causing audio delay
-    let mut hw_params_copy = hw_params.clone();
-    if let Err(_) = hw_params.set_buffer_time_near(100_000, alsa::ValueOr::Nearest) {
-        // Swap out the params with errors for a snapshot taken before the error was introduced.
-        mem::swap(&mut hw_params_copy, &mut hw_params);
-    }
-
     pcm_handle.hw_params(&hw_params)?;
 
     Ok(hw_params)

src/host/emscripten/mod.rs

@@ -334,7 +334,7 @@ fn audio_callback_fn<D, E>(
         // and there may be underflows
         set_timeout(
             || audio_callback_fn::<D, E>(user_data_ptr, config, sample_format, buffer_size_frames),
-            330,
+            buffer_size_frames * 1000 / sample_rate,
         );
     }
 }

src/lib.rs

@@ -183,6 +183,13 @@ pub struct SampleRate(pub u32);
 /// The desired number of frames for the hardware buffer.
 pub type FrameCount = u32;
 
+/// The buffer size used by the device.
+///
+/// Default is used when no specific buffer size is set and uses the default
+/// behavior of the given host. Note, the default buffer size may be surprisingly
+/// large, leading to latency issues. If low latency is desired, Fixed(BufferSize)
+/// should be used in accordance with the SupportedBufferSize range produced by
+/// the SupportedStreamConfig API.  
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub enum BufferSize {
     Default,