feat: add transcript endpoint (#211)

pkg/whisper/whisper.go

@@ -0,0 +1,93 @@
+package whisper
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+
+	"github.com/ggerganov/whisper.cpp/bindings/go/pkg/whisper"
+	wav "github.com/go-audio/wav"
+)
+
+func sh(c string) (string, error) {
+	cmd := exec.Command("/bin/sh", "-c", c)
+	cmd.Env = os.Environ()
+	o, err := cmd.CombinedOutput()
+	return string(o), err
+}
+
+// AudioToWav converts audio to wav for transcribe. It bashes out to ffmpeg
+// TODO: use https://github.com/mccoyst/ogg?
+func audioToWav(src, dst string) error {
+	out, err := sh(fmt.Sprintf("ffmpeg -i %s -format s16le -ar 16000 -ac 1 -acodec pcm_s16le %s", src, dst))
+	if err != nil {
+		return fmt.Errorf("error: %w out: %s", err, out)
+	}
+
+	return nil
+}
+
+func Transcript(modelpath, audiopath, language string) (string, error) {
+
+	dir, err := os.MkdirTemp("", "whisper")
+	if err != nil {
+		return "", err
+	}
+	defer os.RemoveAll(dir)
+
+	convertedPath := filepath.Join(dir, "converted.wav")
+
+	if err := audioToWav(audiopath, convertedPath); err != nil {
+		return "", err
+	}
+
+	// Open samples
+	fh, err := os.Open(convertedPath)
+	if err != nil {
+		return "", err
+	}
+	defer fh.Close()
+
+	// Read samples
+	d := wav.NewDecoder(fh)
+	buf, err := d.FullPCMBuffer()
+	if err != nil {
+		return "", err
+	}
+
+	data := buf.AsFloat32Buffer().Data
+
+	// Load the model
+	model, err := whisper.New(modelpath)
+	if err != nil {
+		return "", err
+	}
+	defer model.Close()
+
+	// Process samples
+	context, err := model.NewContext()
+	if err != nil {
+		return "", err
+
+	}
+
+	if language != "" {
+		context.SetLanguage(language)
+	}
+
+	if err := context.Process(data, nil); err != nil {
+		return "", err
+	}
+
+	text := ""
+	for {
+		segment, err := context.NextSegment()
+		if err != nil {
+			break
+		}
+		text += segment.Text
+	}
+
+	return text, nil
+}