audio: add Streamer interface

audio/interface.go

@@ -0,0 +1,38 @@
+package audio
+
+// SampleRate is the number of audio samples a Streamer should produce per one second of audio.
+//
+// This value should be set at most once before using audio package. It is safe to rely on the fact,
+// that this value does not change during runtime.
+var SampleRate = 48000
+
+// Streamer is able to stream a finite or infinite sequence of audio samples.
+type Streamer interface {
+	// Stream copies at most len(samples) next audio samples to the samples slice.
+	//
+	// The sample rate of the samples is specified by the global SampleRate variable/constant.
+	// The value at samples[i][0] is the value of the left channel of the i-th sample.
+	// Similarly, samples[i][1] is the value of the right channel of the i-th sample.
+	//
+	// Stream returns the number of streamed samples. If the Streamer is drained and no more
+	// samples will be produced, it returns 0 and false. Stream must not touch any samples
+	// outside samples[:n].
+	//
+	// There are 3 valid return pattterns of the Stream method:
+	//
+	//   1. n == len(samples) && ok
+	//
+	// Stream streamed all of the requested samples. Cases 1, 2 and 3 may occur in the following
+	// calls.
+	//
+	//   2. 0 < n && n < len(samples) && ok
+	//
+	// Stream streamed n samples and drained the Streamer. Only case 3 may occur in the
+	// following calls.
+	//
+	//   3. n == 0 && !ok
+	//
+	// The Streamer is drained and no more samples will come. Only this case may occur in the
+	// following calls.
+	Stream(samples [][2]float64) (n int, ok bool)
+}