Initial push to gitea

internal/audio/audio.go

@@ -0,0 +1,42 @@
+// Package audio normalizes arbitrary audio/video inputs into a whisper.cpp-friendly
+// 16 kHz mono PCM WAV file using ffmpeg.
+package audio
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+)
+
+// ExtractWAV runs ffmpeg to convert input (audio or video) into a 16kHz mono
+// signed-16-bit PCM WAV file at outPath. ffmpeg must be on PATH.
+func ExtractWAV(ctx context.Context, input, outPath string) error {
+	if _, err := exec.LookPath("ffmpeg"); err != nil {
+		return fmt.Errorf("ffmpeg not found on PATH: %w", err)
+	}
+	if _, err := os.Stat(input); err != nil {
+		return fmt.Errorf("input not readable: %w", err)
+	}
+	if err := os.MkdirAll(filepath.Dir(outPath), 0o755); err != nil {
+		return err
+	}
+
+	cmd := exec.CommandContext(ctx, "ffmpeg",
+		"-y",
+		"-loglevel", "error",
+		"-i", input,
+		"-vn",
+		"-ac", "1",
+		"-ar", "16000",
+		"-c:a", "pcm_s16le",
+		outPath,
+	)
+	cmd.Stdout = os.Stderr
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("ffmpeg: %w", err)
+	}
+	return nil
+}