ffmpeg

package main

import (
	"bufio"
	"encoding/binary"
	"io"
	"io/ioutil"
	"log"
	"os/exec"
)

func main() {
	cmd := exec.Command("ffmpeg", "-i", "test.mp3",
		"-f", "s16le", "-ar", "48000", "-ac", "2", "pipe:1")
	stdout, _ := cmd.StdoutPipe()
	wait := make(chan bool)
	go func() {
		cmd.Run()
		wait <- true
	}()

	stdin := bufio.NewReaderSize(stdout, 16384)
	encodePCM := func(in []byte) {
		err := ioutil.WriteFile("1.data", in, 0777)
		if err != nil {
			panic(err)
		}
		cmd := exec.Command("opusenc", "--discard-comments", "--raw", "1.data", "1.opus")

		cmd.Run()

		buf, _ := ioutil.ReadFile("1.opus")
		log.Println(len(buf))
	}

	for {

		buf := make([]byte, 960*2*2)

		err := binary.Read(stdin, binary.LittleEndian, &buf)
		if err == io.EOF {
			break
		}
		if err == io.ErrUnexpectedEOF {
			encodePCM(buf)
			break
		}
		if err != nil {
			panic(err)
			break
		}
		encodePCM(buf)
	}

	select {
	case <-wait:
	}
}