using System;
using System.Collections.Generic;
using System.Text;
namespace LumiSoft.Net.Media.Codec.Audio
{
/// <summary>
/// Implements PCMA(G711 alaw) codec.
/// </summary>
public class PCMA : AudioCodec
{
#region byte[] ALawCompressTable
private static readonly byte[] ALawCompressTable = new byte[]{
1,1,2,2,3,3,3,3,
4,4,4,4,4,4,4,4,
5,5,5,5,5,5,5,5,
5,5,5,5,5,5,5,5,
6,6,6,6,6,6,6,6,
6,6,6,6,6,6,6,6,
6,6,6,6,6,6,6,6,
6,6,6,6,6,6,6,6,
7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7
};
#endregion
#region short[] ALawDecompressTable
private static readonly short[] ALawDecompressTable = new short[]{
-5504, -5248, -6016, -5760, -4480, -4224, -4992, -4736,
-7552, -7296, -8064, -7808, -6528, -6272, -7040, -6784,
-2752, -2624, -3008, -2880, -2240, -2112, -2496, -2368,
-3776, -3648, -4032, -3904, -3264, -3136, -3520, -3392,
-22016,-20992,-24064,-23040,-17920,-16896,-19968,-18944,
-30208,-29184,-32256,-31232,-26112,-25088,-28160,-27136,
-11008,-10496,-12032,-11520,-8960, -8448, -9984, -9472,
-15104,-14592,-16128,-15616,-13056,-12544,-14080,-13568,
-344, -328, -376, -360, -280, -264, -312, -296,
-472, -456, -504, -488, -408, -392, -440, -424,
-88, -72, -120, -104, -24, -8, -56, -40,
-216, -200, -248, -232, -152, -136, -184, -168,
-1376, -1312, -1504, -1440, -1120, -1056, -1248, -1184,
-1888, -1824, -2016, -1952, -1632, -1568, -1760, -1696,
-688, -656, -752, -720, -560, -528, -624, -592,
-944, -912, -1008, -976, -816, -784, -880, -848,
5504, 5248, 6016, 5760, 4480, 4224, 4992, 4736,
7552, 7296, 8064, 7808, 6528, 6272, 7040, 6784,
2752, 2624, 3008, 2880, 2240, 2112, 2496, 2368,
3776, 3648, 4032, 3904, 3264, 3136, 3520, 3392,
22016, 20992, 24064, 23040, 17920, 16896, 19968, 18944,
30208, 29184, 32256, 31232, 26112, 25088, 28160, 27136,
11008, 10496, 12032, 11520, 8960, 8448, 9984, 9472,
15104, 14592, 16128, 15616, 13056, 12544, 14080, 13568,
344, 328, 376, 360, 280, 264, 312, 296,
472, 456, 504, 488, 408, 392, 440, 424,
88, 72, 120, 104, 24, 8, 56, 40,
216, 200, 248, 232, 152, 136, 184, 168,
1376, 1312, 1504, 1440, 1120, 1056, 1248, 1184,
1888, 1824, 2016, 1952, 1632, 1568, 1760, 1696,
688, 656, 752, 720, 560, 528, 624, 592,
944, 912, 1008, 976, 816, 784, 880, 848
};
#endregion
private AudioFormat m_pAudioFormat = new AudioFormat(8000,16,1);
private AudioFormat m_pCompressedAudioFormat = new AudioFormat(8000,8,1);
/// <summary>
/// Default constructor.
/// </summary>
public PCMA()
{
}
#region method Encode
/// <summary>
/// Encodes linear 16-bit linear PCM to 8-bit alaw.
/// </summary>
/// <param name="buffer">Data to encode. Data must be in Little-Endian format.</param>
/// <param name="offset">Offset in the buffer.</param>
/// <param name="count">Number of bytes to encode.</param>
/// <returns>Returns encoded block.</returns>
/// <exception cref="ArgumentNullException">Is raised when <b>buffer</b> is null reference.</exception>
/// <exception cref="ArgumentException">Is raised when any of the arguments has invalid value.</exception>
public override byte[] Encode(byte[] buffer,int offset,int count)
{
if(buffer == null){
throw new ArgumentNullException("buffer");
}
if(offset < 0 || offset > buffer.Length){
throw new ArgumentException("Argument 'offset' is out of range.");
}
if(count < 1 || (count + offset) > buffer.Length){
throw new ArgumentException("Argument 'count' is out of range.");
}
if((count % 2) != 0){
throw new ArgumentException("Invalid 'count' value, it doesn't contain 16-bit boundaries.");
}
int offsetInRetVal = 0;
byte[] retVal = new byte[count / 2];
while(offsetInRetVal < retVal.Length){
// Little-Endian - lower byte,higer byte.
short pcm = (short)(buffer[offset + 1] << 8 | buffer[offset]);
offset += 2;
retVal[offsetInRetVal++] = LinearToALawSample(pcm);
}
return retVal;
}
#endregion
#region method Decode
/// <summary>
/// Decodes 8-bit alaw to linear 16-bit PCM.
/// </summary>
/// <param name="buffer">Data to decode. Data must be in Little-Endian format.</param>
/// <param name="offset">Offset in the buffer.</param>
/// <param name="count">Number of bytes to decode.</param>
/// <returns>Returns decoded data.</returns>
/// <exception cref="ArgumentNullException">Is raised when <b>buffer</b> is null reference.</exception>
/// <exception cref="ArgumentException">Is raised when any of the arguments has invalid value.</exception>
public override byte[] Decode(byte[] buffer,int offset,int count)
{
if(buffer == null){
throw new ArgumentNullException("buffer");
}
if(offset < 0 || offset > buffer.Length){
throw new ArgumentException("Argument 'offse't is out of range.");
}
if(count < 1 || (count + offset) > buffer.Length){
throw new ArgumentException("Argument 'count' is out of range.");
}
int offsetInRetVal = 0;
byte[] retVal = new byte[count * 2];
for(int i=offset;i<buffer.Length;i++){
short pcm = ALawDecompressTable[buffer[i]];
retVal[offsetInRetVal++] = (byte)(pcm & 0xFF);
retVal[offsetInRetVal++] = (byte)(pcm >> 8 & 0xFF);
}
return retVal;
}
#endregion
#region static method LinearToALawSample
private static byte LinearToALawSample(short sample)
{
int sign = 0;
int exponent = 0;
int mantissa = 0;
byte compressedByte = 0;
sign = ((~sample) >> 8) & 0x80;
if(sign == 0){
sample = (short)-sample;
}
if(sample > 32635){
sample = 32635;
}
if(sample >= 256){
exponent = (int)ALawCompressTable[(sample >> 8) & 0x7F];
mantissa = (sample >> (exponent + 3) ) & 0x0F;
compressedByte = (byte)((exponent << 4) | mantissa);
}
else{
compressedByte = (byte)(sample >> 4);
}
compressedByte ^= (byte)(sign ^ 0x55);
return compressedByte;
}
#endregion
#region Properties implementation
/// <summary>
/// Gets codec name.
/// </summary>
public override string Name
{
get{ return "PCMA"; }
}
/// <summary>
/// Gets uncompressed audio format info.
/// </summary>
public override AudioFormat AudioFormat
{
get{ return m_pAudioFormat; }
}
/// <summary>
/// Gets compressed audio format info.
/// </summary>
public override AudioFormat CompressedAudioFormat
{
get{ return m_pCompressedAudioFormat; }
}
#endregion
}
}
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