fix: untangle pkg/grpc and core/schema for Transcription (#3419)

untangle pkg/grpc and core/schema in Transcribe

Signed-off-by: Dave Lee <dave@gray101.com>

pkg/utils/ffmpeg.go

@@ -0,0 +1,25 @@
+package utils
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+)
+
+func ffmpegCommand(args []string) (string, error) {
+	cmd := exec.Command("ffmpeg", args...) // Constrain this to ffmpeg to permit security scanner to see that the command is safe.
+	cmd.Env = os.Environ()
+	out, err := cmd.CombinedOutput()
+	return string(out), err
+}
+
+// AudioToWav converts audio to wav for transcribe.
+// TODO: use https://github.com/mccoyst/ogg?
+func AudioToWav(src, dst string) error {
+	commandArgs := []string{"-i", src, "-format", "s16le", "-ar", "16000", "-ac", "1", "-acodec", "pcm_s16le", dst}
+	out, err := ffmpegCommand(commandArgs)
+	if err != nil {
+		return fmt.Errorf("error: %w out: %s", err, out)
+	}
+	return nil
+}