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

/*
NAME
  decode-pcm.go

DESCRIPTION
  decode-pcm.go is a program for decoding/decompressing an adpcm file to a pcm file.

AUTHOR
  Trek Hopton <trek@ausocean.org>

LICENSE
  decode-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 file encoded in adpcm and outputs a decoded pcm file.
// Input and output file names can be specified as arguments.
func main() {
	var inPath string
	var outPath string
	flag.StringVar(&inPath, "in", "encoded.adpcm", "file path of input")
	flag.StringVar(&outPath, "out", "decoded.pcm", "file path of output data")
	flag.Parse()

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

	// decode adpcm
	inBSize := 256
	numBlocks := len(comp) / inBSize
	outBSize := 2 + (inBSize-4)*4 // 2 bytes are copied, 2 are used as block header info, the remaining bytes are decompressed 1:4
	decoded := bytes.NewBuffer(make([]byte, 0, outBSize*numBlocks))
	dec := adpcm.NewDecoder(decoded)
	for i := 0; i < numBlocks; i++ {
		block := comp[inBSize*i : inBSize*(i+1)]
		err := dec.DecodeBlock(block)
		if err != nil {
			log.Fatal(err)
		}
	}

	// save pcm to file
	err = ioutil.WriteFile(outPath, decoded.Bytes(), 0644)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("Decoded and wrote", len(decoded.Bytes()), "bytes to file", outPath)
}