get rid of global SampleRate - remove time tracking from Ctrl and Take now takes number of samples

compositors.go

@@ -1,18 +1,13 @@
 package beep
 
-import (
-	"math"
-	"time"
-)
-
-// Take returns a Streamer which streams s for at most d duration.
+// Take returns a Streamer which streams at most n samples from s.
 //
 // The returned Streamer propagates s's errors throught Err.
-func Take(d time.Duration, s Streamer) Streamer {
+func Take(n int, s Streamer) Streamer {
 	return &take{
 		s:          s,
 		currSample: 0,
-		numSamples: int(math.Ceil(d.Seconds() * float64(SampleRate))),
+		numSamples: n,
 	}
 }
 

ctrl.go

@@ -1,8 +1,6 @@
 package beep
 
-import "time"
-
-// Ctrl allows for pausing and tracking a Streamer.
+// Ctrl allows for pausing a Streamer.
 //
 // Wrap a Streamer in a Ctrl.
 //
@@ -12,11 +10,6 @@ import "time"
 //
 //   ctrl.Paused = true
 //
-// And we can check how much has already been streamed. Position is not incremented when the Ctrl is
-// paused.
-//
-//   fmt.Println(ctrl.Position)
-//
 // To completely stop a Ctrl before the wrapped Streamer is drained, just set the wrapped Streamer
 // to nil.
 //
@@ -30,14 +23,9 @@ import "time"
 //   speaker.Lock()
 //   ctrl.Paused = true
 //   speaker.Unlock()
-//   // ...
-//   speaker.Lock()
-//   fmt.Println(ctrl.Position)
-//   speaker.Unlock()
 type Ctrl struct {
 	Streamer Streamer
 	Paused   bool
-	Position time.Duration
 }
 
 // Stream streams the wrapped Streamer, if not nil. If the Streamer is nil, Ctrl acts as drained.
@@ -52,9 +40,7 @@ func (c *Ctrl) Stream(samples [][2]float64) (n int, ok bool) {
 		}
 		return len(samples), true
 	}
-	n, ok = c.Streamer.Stream(samples)
-	c.Position += time.Duration(n) * time.Second / time.Duration(SampleRate)
-	return n, ok
+	return c.Streamer.Stream(samples)
 }
 
 // Err returns the error of the wrapped Streamer, if not nil.

interface.go

@@ -2,12 +2,6 @@ package beep
 
 import "time"
 
-// 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 assume 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.

speaker/speaker.go

@@ -19,13 +19,12 @@ var (
 	done    chan struct{}
 )
 
-// Init initializes audio playback through speaker. Must be called before using this package. The
-// value of beep.SampleRate must be set (or left to the default) before calling this function.
+// Init initializes audio playback through speaker. Must be called before using this package.
 //
 // The bufferSize argument specifies the length of the speaker's buffer. Bigger bufferSize means
 // lower CPU usage and more reliable playback. Lower bufferSize means better responsiveness and less
 // delay.
-func Init(bufferSize time.Duration) error {
+func Init(sampleRate int, bufferSize time.Duration) error {
 	mu.Lock()
 	defer mu.Unlock()
 
@@ -36,14 +35,14 @@ func Init(bufferSize time.Duration) error {
 
 	mixer = beep.Mixer{}
 
-	numSamples := int(math.Ceil(bufferSize.Seconds() * float64(beep.SampleRate)))
+	numSamples := int(math.Ceil(bufferSize.Seconds() * float64(sampleRate)))
 	numBytes := numSamples * 4
 
 	samples = make([][2]float64, numSamples)
 	buf = make([]byte, numBytes)
 
 	var err error
-	player, err = oto.NewPlayer(int(beep.SampleRate), 2, 2, numBytes)
+	player, err = oto.NewPlayer(sampleRate, 2, 2, numBytes)
 	if err != nil {
 		return errors.Wrap(err, "failed to initialize speaker")
 	}