av/cmd/audio-player/looper/main.go

/*
NAME
  audio-player/looper/main.go

AUTHORS
  Ella Pietraroia <ella@ausocean.org>

LICENSE
  audio player is Copyright (C) 2020 the Australian Ocean Lab (AusOcean)

  It is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  for more details.

  You should have received a copy of the GNU General Public License
  in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

// Audio looper.
package main

import (
	"bytes"
	"io"
	"log"
	"os"
	"os/exec"
	"sync"
)

func main() {
	const soundFile = "/home/pi/48khz.wav"
	const logFile = "audio.log"

	// Making log file.
	_, err := os.Stat(logFile)
	if !os.IsNotExist(err) {
		err := os.Remove(logFile)
		if err != nil {
			log.Fatalf("fatal: error clearing file: %v", err)
		}
	}

	f, err := os.OpenFile(logFile, os.O_RDWR|os.O_CREATE, 0666)
	if err != nil {
		log.Fatalf("fatal: error opening file %s: %v", logFile, err)
	}
	defer f.Close()
	log.SetOutput(f)

	// Pi model specific initialisation
	initCommand()

	// Infinite loop that outputs audio and gathers debug information.
	numPlays := 0
	for {
		numPlays++
		log.Printf("debug: play number: %d\n", numPlays)

		cmd := exec.Command(audioCmd, soundFile)

		var stdoutBuf, stderrBuf bytes.Buffer
		stdoutIn, _ := cmd.StdoutPipe()
		stderrIn, _ := cmd.StderrPipe()

		var errStdout, errStderr error
		stdout := io.MultiWriter(os.Stdout, &stdoutBuf)
		stderr := io.MultiWriter(os.Stderr, &stderrBuf)

		err := cmd.Start()
		if err != nil {
			log.Fatalf("fatal: cmd.Start() for 'play' failed with '%s'\n", err)
		}

		var wg sync.WaitGroup
		wg.Add(1)

		go func() {
			_, errStdout = io.Copy(stdout, stdoutIn)
			wg.Done()
		}()

		_, errStderr = io.Copy(stderr, stderrIn)
		wg.Wait()

		err = cmd.Wait()
		if err != nil {
			log.Fatalf("fatal: cmd.Run() for 'play' failed with %s\n", err)
		}
		if errStdout != nil || errStderr != nil {
			log.Fatal("fatal: failed to capture stdout or stderr\n")
		}
		outStr, errStr := string(stdoutBuf.Bytes()), string(stderrBuf.Bytes())
		log.Printf("\nout:\n%s\nerr:\n%s\n____________________________________________________\n\n", outStr, errStr)
	}

}