audio/internal/convert: Add resampling_test.go

Fixes #369

.travis.yml

@@ -38,6 +38,7 @@ before_script:
 script:
   - go build -tags example -v github.com/hajimehoshi/ebiten/examples/...
   - go test -v github.com/hajimehoshi/ebiten
+  - go test -v github.com/hajimehoshi/ebiten/audio/internal/convert
   - go test -v github.com/hajimehoshi/ebiten/internal/math
   - go test -v github.com/hajimehoshi/ebiten/internal/restorable
   - gopherjs build --tags example -v github.com/hajimehoshi/ebiten/examples/blocks

audio/internal/convert/resampling_test.go

@@ -0,0 +1,96 @@
+// Copyright 2018 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package convert_test
+
+import (
+	"io/ioutil"
+	"math"
+	"testing"
+
+	"github.com/hajimehoshi/ebiten/audio"
+	. "github.com/hajimehoshi/ebiten/audio/internal/convert"
+)
+
+func soundAt(timeInSecond float64) float64 {
+	const freq = 220
+
+	amp := []float64{1.0, 0.8, 0.6, 0.4, 0.2}
+	v := 0.0
+	for j := 0; j < len(amp); j++ {
+		v += amp[j] * math.Sin(2.0*math.Pi*timeInSecond*freq*float64(j+1))
+	}
+	if v > 1 {
+		v = 1
+	}
+	if v < -1 {
+		v = -1
+	}
+	return v
+}
+
+func newSoundBytes(sampleRate int) []byte {
+	b := make([]byte, sampleRate*4) // 1 second
+	for i := 0; i < len(b)/4; i++ {
+		v := soundAt(float64(i) / float64(sampleRate))
+		v16 := int16(v * (1<<15 - 1))
+		b[4*i] = byte(v16)
+		b[4*i+1] = byte(v16 >> 8)
+		b[4*i+2] = byte(v16)
+		b[4*i+3] = byte(v16 >> 8)
+	}
+	return b
+}
+
+func abs(x int) int {
+	if x < 0 {
+		return -x
+	}
+	return x
+}
+
+func TestResampling(t *testing.T) {
+	cases := []struct {
+		In  int
+		Out int
+	}{
+		{
+			In:  44100,
+			Out: 48000,
+		},
+		{
+			In:  48000,
+			Out: 44100,
+		},
+	}
+	for _, c := range cases {
+		inB := newSoundBytes(c.In)
+		outS := NewResampling(audio.BytesReadSeekCloser(inB), int64(len(inB)), c.In, c.Out)
+		gotB, err := ioutil.ReadAll(outS)
+		if err != nil {
+			t.Fatal(err)
+		}
+		wantB := newSoundBytes(c.Out)
+		if len(gotB) != len(wantB) {
+			t.Errorf("len(gotB) == %d but len(wantB) == %d", len(gotB), len(wantB))
+		}
+		for i := 0; i < len(gotB)/2; i++ {
+			got := float64(int16(gotB[2*i])|(int16(gotB[2*i+1])<<8)) / (1<<15 - 1)
+			want := float64(int16(wantB[2*i])|(int16(wantB[2*i+1])<<8)) / (1<<15 - 1)
+			if math.Abs(got-want) > 0.025 {
+				t.Errorf("sample rate: %d, index: %d: got: %f, want: %f", c.Out, i, got, want)
+			}
+		}
+	}
+}