namespace LumiSoft.Net.Media.Codec.Audio
{
using System;
using System.Collections.Generic;
using System.Text;
/// <summary>
/// Implements PCMU(G711 ulaw) codec.
/// </summary>
public class PCMU : AudioCodec
{
#region Fields
private static readonly byte[] MuLawCompressTable = new byte[]{
0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
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,
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,
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
};
private static readonly short[] MuLawDecompressTable = new short[]{
-32124,-31100,-30076,-29052,-28028,-27004,-25980,-24956,
-23932,-22908,-21884,-20860,-19836,-18812,-17788,-16764,
-15996,-15484,-14972,-14460,-13948,-13436,-12924,-12412,
-11900,-11388,-10876,-10364, -9852, -9340, -8828, -8316,
-7932, -7676, -7420, -7164, -6908, -6652, -6396, -6140,
-5884, -5628, -5372, -5116, -4860, -4604, -4348, -4092,
-3900, -3772, -3644, -3516, -3388, -3260, -3132, -3004,
-2876, -2748, -2620, -2492, -2364, -2236, -2108, -1980,
-1884, -1820, -1756, -1692, -1628, -1564, -1500, -1436,
-1372, -1308, -1244, -1180, -1116, -1052, -988, -924,
-876, -844, -812, -780, -748, -716, -684, -652,
-620, -588, -556, -524, -492, -460, -428, -396,
-372, -356, -340, -324, -308, -292, -276, -260,
-244, -228, -212, -196, -180, -164, -148, -132,
-120, -112, -104, -96, -88, -80, -72, -64,
-56, -48, -40, -32, -24, -16, -8, 0,
32124, 31100, 30076, 29052, 28028, 27004, 25980, 24956,
23932, 22908, 21884, 20860, 19836, 18812, 17788, 16764,
15996, 15484, 14972, 14460, 13948, 13436, 12924, 12412,
11900, 11388, 10876, 10364, 9852, 9340, 8828, 8316,
7932, 7676, 7420, 7164, 6908, 6652, 6396, 6140,
5884, 5628, 5372, 5116, 4860, 4604, 4348, 4092,
3900, 3772, 3644, 3516, 3388, 3260, 3132, 3004,
2876, 2748, 2620, 2492, 2364, 2236, 2108, 1980,
1884, 1820, 1756, 1692, 1628, 1564, 1500, 1436,
1372, 1308, 1244, 1180, 1116, 1052, 988, 924,
876, 844, 812, 780, 748, 716, 684, 652,
620, 588, 556, 524, 492, 460, 428, 396,
372, 356, 340, 324, 308, 292, 276, 260,
244, 228, 212, 196, 180, 164, 148, 132,
120, 112, 104, 96, 88, 80, 72, 64,
56, 48, 40, 32, 24, 16, 8, 0
};
#endregion Fields
#region Constructors
/// <summary>
/// Default constructor.
/// </summary>
public PCMU()
{
}
#endregion Constructors
#region Properties
/// <summary>
/// Gets number of bits per sample.
/// </summary>
public override int BitsPerSample
{
get{ return 8; }
}
/// <summary>
/// Gets codec name.
/// </summary>
public override string Name
{
get{ return "PCMU"; }
}
/// <summary>
/// Gets sample number of samples in second(hz).
/// </summary>
public override int SampleRate
{
get{ return 8000; }
}
#endregion Properties
#region Methods
/// <summary>
/// Decodes 8-bit ulaw 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 riased when <b>buffer</b> is null reference value.</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 'offset' 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 = MuLawDecompressTable[buffer[i]];
retVal[offsetInRetVal++] = (byte)(pcm & 0xFF);
retVal[offsetInRetVal++] = (byte)(pcm >> 8 & 0xFF);
}
return retVal;
}
/// <summary>
/// Encodes linear 16-bit linear PCM to 8-bit ulaw.
/// </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 value.</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 buufer 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++] = LinearToMuLawSample(pcm);
}
return retVal;
}
private static byte LinearToMuLawSample(short sample)
{
int cBias = 0x84;
int cClip = 32635;
int sign = (sample >> 8) & 0x80;
if(sign != 0){
sample = (short)-sample;
}
if(sample > cClip){
sample = (short)cClip;
}
sample = (short)(sample + cBias);
int exponent = (int)MuLawCompressTable[(sample>>7) & 0xFF];
int mantissa = (sample >> (exponent+3)) & 0x0F;
int compressedByte = ~(sign | (exponent << 4) | mantissa);
return (byte)compressedByte;
}
#endregion Methods
}
}