google_speech.go

package main

import (
	"bytes"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"
)

func main() {
	f, err := os.Open("./sample.wav")
	if err != nil {
		log.Fatal(err)
	}
	b, err := ioutil.ReadAll(f)
	if err != nil {
		log.Fatal(err)
	}

	text, err := fetchTranscription(b)
	if err != nil {
		log.Fatal("couldn't transcribe:", err)
	}
	fmt.Println(text)
}

type speechReq struct {
	Config struct {
		Encoding   string `json:"encoding"`
		SampleRate int    `json:"sampleRate"`
	} `json:"config"`
	Audio struct {
		Content string `json:"content"`
	} `json:"audio"`
}

func fetchTranscription(b []byte) (string, error) {
	var req speechReq
	req.Config.Encoding = "LINEAR16"
	req.Config.SampleRate = 16000
	req.Audio.Content = base64.StdEncoding.EncodeToString(b)

	j, err := json.Marshal(req)
	if err != nil {
		return "", fmt.Errorf("could not encode request: %v", err)
	}

	client := &http.Client{}
	request, err := http.NewRequest("POST", "https://speech.googleapis.com/v1beta1/speech:syncrecognize?key="+os.Getenv("GOOGLE_SPEECH_API"), bytes.NewReader(j))
	if err != nil {
		return "", fmt.Errorf("couldn't not transcribe: %v", err)
	}
	res, err := client.Do(request)
	if err != nil {
		return "", err
	}

	var data struct {
		Error struct {
			Code    int
			Message string
			Status  string
		}
		Results []struct {
			Alternatives []struct {
				Transcript string
				Confidence float64
			}
		}
	}

	if err := json.NewDecoder(res.Body).Decode(&data); err != nil {
		return "", fmt.Errorf("couldn't decode response: %v", err)
	}
	if data.Error.Code != 0 {
		return "", fmt.Errorf("speech API error: %d %s %s",
			data.Error.Code, data.Error.Status, data.Error.Message)
	}
	if len(data.Results) == 0 || len(data.Results[0].Alternatives) == 0 {
		return "", fmt.Errorf("no transcription found: %+v", data)
	}
	return data.Results[0].Alternatives[0].Transcript, nil
}