feat: parse wav metadata for offline audio source

internal/audio/wav.go

@@ -8,8 +8,10 @@ import (
 )
 
 type WAVSource struct {
-    frames []Frame
-    index  int
+    frames      []Frame
+    index       int
+    SampleRate  int
+    Channels    int
 }
 
 func LoadWAVSource(path string) (*WAVSource, error) {
@@ -27,16 +29,24 @@ func LoadWAVSource(path string) (*WAVSource, error) {
         return nil, fmt.Errorf("unsupported wav header")
     }
 
+    audioFormat := binary.LittleEndian.Uint16(header[20:22])
     channels := binary.LittleEndian.Uint16(header[22:24])
+    sampleRate := binary.LittleEndian.Uint32(header[24:28])
     bitsPerSample := binary.LittleEndian.Uint16(header[34:36])
     dataSize := binary.LittleEndian.Uint32(header[40:44])
 
+    if audioFormat != 1 {
+        return nil, fmt.Errorf("only PCM wav supported")
+    }
     if bitsPerSample != 16 {
         return nil, fmt.Errorf("only 16-bit PCM wav supported")
     }
     if channels != 1 && channels != 2 {
         return nil, fmt.Errorf("only mono/stereo wav supported")
     }
+    if sampleRate == 0 {
+        return nil, fmt.Errorf("invalid wav sample rate")
+    }
 
     raw := make([]byte, dataSize)
     if _, err := io.ReadFull(f, raw); err != nil {
@@ -54,7 +64,11 @@ func LoadWAVSource(path string) (*WAVSource, error) {
         frames = append(frames, NewFrame(l, r))
     }
 
-    return &WAVSource{frames: frames}, nil
+    return &WAVSource{
+        frames:     frames,
+        SampleRate: int(sampleRate),
+        Channels:   int(channels),
+    }, nil
 }
 
 func (s *WAVSource) NextFrame() Frame {

internal/audio/wav_test.go

@@ -28,5 +28,11 @@ func TestLoadWAVSource(t *testing.T) {
     if err != nil {
         t.Fatalf("LoadWAVSource failed: %v", err)
     }
+    if src.SampleRate != 48000 {
+        t.Fatalf("unexpected sample rate: %d", src.SampleRate)
+    }
+    if src.Channels != 1 {
+        t.Fatalf("unexpected channels: %d", src.Channels)
+    }
     _ = src.NextFrame()
 }