Implement async method decode_audio_data (however still blocking IO)

src/context/base.rs

@@ -12,6 +12,8 @@ use crate::param::AudioParamDescriptor;
 use crate::periodic_wave::{PeriodicWave, PeriodicWaveOptions};
 use crate::{node, AudioListener};
 
+use std::future::Future;
+
 /// The interface representing an audio-processing graph built from audio modules linked together,
 /// each represented by an `AudioNode`.
 ///
@@ -29,11 +31,11 @@ pub trait BaseAudioContext {
     ///
     /// In addition to the official spec, the input parameter can be any byte stream (not just an
     /// array). This means you can decode audio data from a file, network stream, or in memory
-    /// buffer, and any other [`std::io::Read`] implementer. The data if buffered internally so you
+    /// buffer, and any other [`std::io::Read`] implementer. The data is buffered internally so you
     /// should not wrap the source in a `BufReader`.
     ///
     /// This function operates synchronously, which may be undesirable on the control thread. The
-    /// example shows how to avoid this. An async version is currently not implemented.
+    /// example shows how to avoid this. See also the async method [`Self::decode_audio_data`].
     ///
     /// # Errors
     ///
@@ -82,6 +84,50 @@ pub trait BaseAudioContext {
         Ok(buffer)
     }
 
+    /// Decode an [`AudioBuffer`] from a given input stream.
+    ///
+    /// The current implementation can decode FLAC, Opus, PCM, Vorbis, and Wav.
+    ///
+    /// In addition to the official spec, the input parameter can be any byte stream (not just an
+    /// array). This means you can decode audio data from a file, network stream, or in memory
+    /// buffer, and any other [`std::io::Read`] implementer. The data is buffered internally so you
+    /// should not wrap the source in a `BufReader`.
+    ///
+    /// Warning, the current implementation still uses blocking IO so it's best to use Tokio's
+    /// `spawn_blocking` to run the decoding on a thread dedicated to blocking operations. See also
+    /// the async method [`Self::decode_audio_data_sync`].
+    ///
+    /// # Errors
+    ///
+    /// This method returns an Error in various cases (IO, mime sniffing, decoding).
+    // Use of `async fn` in public traits is discouraged as auto trait bounds cannot be specified,
+    // hence we use `-> impl Future + ..` instead.
+    fn decode_audio_data<R: std::io::Read + Send + Sync + 'static>(
+        &self,
+        input: R,
+    ) -> impl Future<Output = Result<AudioBuffer, Box<dyn std::error::Error + Send + Sync>>>
+           + Send
+           + 'static {
+        let sample_rate = self.sample_rate();
+        async move {
+            // Set up a media decoder, consume the stream in full and construct a single buffer out of it
+            let mut buffer = MediaDecoder::try_new(input)?
+                .collect::<Result<Vec<_>, _>>()?
+                .into_iter()
+                .reduce(|mut accum, item| {
+                    accum.extend(&item);
+                    accum
+                })
+                // if there are no samples decoded, return an empty buffer
+                .unwrap_or_else(|| AudioBuffer::from(vec![vec![]], sample_rate));
+
+            // resample to desired rate (no-op if already matching)
+            buffer.resample(sample_rate);
+
+            Ok(buffer)
+        }
+    }
+
     /// Create an new "in-memory" `AudioBuffer` with the given number of channels,
     /// length (i.e. number of samples per channel) and sample rate.
     ///
@@ -339,3 +385,88 @@ pub trait BaseAudioContext {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::context::OfflineAudioContext;
+
+    use float_eq::assert_float_eq;
+
+    fn require_send_sync_static<T: Send + Sync + 'static>(_: T) {}
+
+    #[test]
+    fn test_decode_audio_data_sync() {
+        let context = OfflineAudioContext::new(1, 1, 44100.);
+        let file = std::fs::File::open("samples/sample.wav").unwrap();
+        let audio_buffer = context.decode_audio_data_sync(file).unwrap();
+
+        assert_eq!(audio_buffer.sample_rate(), 44100.);
+        assert_eq!(audio_buffer.length(), 142_187);
+        assert_eq!(audio_buffer.number_of_channels(), 2);
+        assert_float_eq!(audio_buffer.duration(), 3.224, abs_all <= 0.001);
+
+        let left_start = &audio_buffer.get_channel_data(0)[0..100];
+        let right_start = &audio_buffer.get_channel_data(1)[0..100];
+        // assert distinct two channel data
+        assert!(left_start != right_start);
+    }
+
+    #[test]
+    fn test_decode_audio_data_future_send_static() {
+        let context = OfflineAudioContext::new(1, 1, 44100.);
+        let file = std::fs::File::open("samples/sample.wav").unwrap();
+        let future = context.decode_audio_data(file);
+        require_send_sync_static(future);
+    }
+
+    #[test]
+    fn test_decode_audio_data_async() {
+        use futures::executor;
+        let context = OfflineAudioContext::new(1, 1, 44100.);
+        let file = std::fs::File::open("samples/sample.wav").unwrap();
+        let future = context.decode_audio_data(file);
+        let audio_buffer = executor::block_on(future).unwrap();
+
+        assert_eq!(audio_buffer.sample_rate(), 44100.);
+        assert_eq!(audio_buffer.length(), 142_187);
+        assert_eq!(audio_buffer.number_of_channels(), 2);
+        assert_float_eq!(audio_buffer.duration(), 3.224, abs_all <= 0.001);
+
+        let left_start = &audio_buffer.get_channel_data(0)[0..100];
+        let right_start = &audio_buffer.get_channel_data(1)[0..100];
+        // assert distinct two channel data
+        assert!(left_start != right_start);
+    }
+
+    // #[test]
+    // disabled: symphonia cannot handle empty WAV-files
+    #[allow(dead_code)]
+    fn test_decode_audio_data_empty() {
+        let context = OfflineAudioContext::new(1, 1, 44100.);
+        let file = std::fs::File::open("samples/empty_2c.wav").unwrap();
+        let audio_buffer = context.decode_audio_data_sync(file).unwrap();
+        assert_eq!(audio_buffer.length(), 0);
+    }
+
+    #[test]
+    fn test_decode_audio_data_decoding_error() {
+        let context = OfflineAudioContext::new(1, 1, 44100.);
+        let file = std::fs::File::open("samples/corrupt.wav").unwrap();
+        assert!(context.decode_audio_data_sync(file).is_err());
+    }
+
+    #[test]
+    fn test_create_buffer() {
+        let number_of_channels = 3;
+        let length = 2000;
+        let sample_rate = 96_000.;
+
+        let context = OfflineAudioContext::new(1, 1, 44100.);
+        let buffer = context.create_buffer(number_of_channels, length, sample_rate);
+
+        assert_eq!(buffer.number_of_channels(), 3);
+        assert_eq!(buffer.length(), 2000);
+        assert_float_eq!(buffer.sample_rate(), 96000., abs_all <= 0.);
+    }
+}

src/context/mod.rs

@@ -146,8 +146,6 @@ mod tests {
     use super::*;
     use crate::node::AudioNode;
 
-    use float_eq::assert_float_eq;
-
     fn require_send_sync_static<T: Send + Sync + 'static>(_: T) {}
 
     #[test]
@@ -156,7 +154,7 @@ mod tests {
         let registration = context.mock_registration();
 
         // we want to be able to ship AudioNodes to another thread, so the Registration should be
-        // Send Sync and 'static
+        // Send, Sync and 'static
         require_send_sync_static(registration);
     }
 
@@ -167,62 +165,17 @@ mod tests {
     }
 
     #[test]
-    fn test_sample_rate_length() {
-        let context = OfflineAudioContext::new(1, 48000, 96000.);
-        assert_float_eq!(context.sample_rate(), 96000., abs_all <= 0.);
-        assert_eq!(context.length(), 48000);
-    }
-
-    #[test]
-    fn test_decode_audio_data() {
-        let context = OfflineAudioContext::new(1, 1, 44100.);
-        let file = std::fs::File::open("samples/sample.wav").unwrap();
-        let audio_buffer = context.decode_audio_data_sync(file).unwrap();
-
-        assert_eq!(audio_buffer.sample_rate(), 44100.);
-        assert_eq!(audio_buffer.length(), 142_187);
-        assert_eq!(audio_buffer.number_of_channels(), 2);
-        assert_float_eq!(audio_buffer.duration(), 3.224, abs_all <= 0.001);
-
-        let left_start = &audio_buffer.get_channel_data(0)[0..100];
-        let right_start = &audio_buffer.get_channel_data(1)[0..100];
-        // assert distinct two channel data
-        assert!(left_start != right_start);
-    }
-
-    // #[test]
-    // disabled: symphonia cannot handle empty WAV-files
-    #[allow(dead_code)]
-    fn test_decode_audio_data_empty() {
-        let context = OfflineAudioContext::new(1, 1, 44100.);
-        let file = std::fs::File::open("samples/empty_2c.wav").unwrap();
-        let audio_buffer = context.decode_audio_data_sync(file).unwrap();
-        assert_eq!(audio_buffer.length(), 0);
-    }
-
-    #[test]
-    fn test_decode_audio_data_decoding_error() {
-        let context = OfflineAudioContext::new(1, 1, 44100.);
-        let file = std::fs::File::open("samples/corrupt.wav").unwrap();
-        assert!(context.decode_audio_data_sync(file).is_err());
-    }
-
-    #[test]
-    fn test_create_buffer() {
-        let number_of_channels = 3;
-        let length = 2000;
-        let sample_rate = 96_000.;
-
-        let context = OfflineAudioContext::new(1, 1, 44100.);
-        let buffer = context.create_buffer(number_of_channels, length, sample_rate);
-
-        assert_eq!(buffer.number_of_channels(), 3);
-        assert_eq!(buffer.length(), 2000);
-        assert_float_eq!(buffer.sample_rate(), 96000., abs_all <= 0.);
+    fn test_online_audio_context_send_sync() {
+        let options = AudioContextOptions {
+            sink_id: "none".into(),
+            ..AudioContextOptions::default()
+        };
+        let context = AudioContext::new(options);
+        require_send_sync_static(context);
     }
 
     #[test]
-    fn test_registration() {
+    fn test_context_equals() {
         let context = OfflineAudioContext::new(1, 48000, 96000.);
         let dest = context.destination();
         assert!(dest.context() == context.base());

src/context/offline.rs

@@ -433,6 +433,13 @@ mod tests {
     use crate::node::AudioNode;
     use crate::node::AudioScheduledSourceNode;
 
+    #[test]
+    fn test_sample_rate_length() {
+        let context = OfflineAudioContext::new(1, 48000, 96000.);
+        assert_float_eq!(context.sample_rate(), 96000., abs_all <= 0.);
+        assert_eq!(context.length(), 48000);
+    }
+
     #[test]
     fn render_empty_graph() {
         let mut context = OfflineAudioContext::new(2, 555, 44_100.);