av/cmd/adpcm/encode-pcm/encode-pcm.go

/*
NAME
  encode-pcm.go

DESCRIPTION
  encode-pcm.go is a program for encoding/compressing a pcm file to an adpcm file.

AUTHOR
  Trek Hopton <trek@ausocean.org>

LICENSE
  encode-pcm.go is Copyright (C) 2018 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 [GNU licenses](http://www.gnu.org/licenses).
*/

package main

import (
	"bytes"
	"flag"
	"fmt"
	"io/ioutil"
	"log"

	"bitbucket.org/ausocean/av/stream/adpcm"
)

// This program accepts an input pcm file and outputs an encoded adpcm file.
// Input and output file names can be specified as arguments.
func main() {
	var inPath string
	var adpcmPath string
	flag.StringVar(&inPath, "in", "data.pcm", "file path of input data")
	flag.StringVar(&adpcmPath, "out", "encoded.adpcm", "file path of output")
	flag.Parse()

	//read pcm
	pcm, err := ioutil.ReadFile(inPath)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("Read", len(pcm), "bytes from file", inPath)

	//encode adpcm
	inBSize := 1010
	numBlocks := len(pcm) / inBSize
	outBSize := int(float64(inBSize)/4 + 3.5) // compression is 4:1 and 3.5 bytes of info are added to each block
	comp := bytes.NewBuffer(make([]byte, 0, outBSize*numBlocks))
	enc := adpcm.NewEncoder(comp)
	for i := 0; i < numBlocks; i++ {
		block := pcm[inBSize*i : inBSize*(i+1)]
		err := enc.EncodeBlock(block)
		if err != nil {
			log.Fatal(err)
		}
	}

	// save adpcm to file
	err = ioutil.WriteFile(adpcmPath, comp.Bytes(), 0644)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("Encoded and wrote", len(comp.Bytes()), "bytes to file", adpcmPath)
}