LspQuant.cs

//
// Copyright (C) 2003 Jean-Marc Valin
// Copyright (C) 1999-2003 Wimba S.A., All Rights Reserved.
// Copyright (C) 2008 Filip Navara
// Copyright (C) 2009-2010 Christoph Fröschl
//
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// modification, are permitted provided that the following conditions
// are met:
// 
// - Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
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// - Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// 
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// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
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namespace NSpeex
{
	/// <summary>
	/// Abstract class that is the base for the various LSP Quantisation and
	/// Unquantisation methods.
	/// </summary>
    internal abstract class LspQuant
	{
		protected const int MAX_LSP_SIZE = 20;

		protected internal LspQuant()
		{
		}

		/// <summary>
		/// Line Spectral Pair Quantification.
		/// </summary>
		public abstract void Quant(float[] lsp, float[] qlsp, int order, Bits bits);

		/// <summary>
		/// Line Spectral Pair Unquantification.
		/// </summary>
		public abstract void Unquant(float[] lsp, int order, Bits bits);

		/// <summary>
		/// Read the next 6 bits from the buffer, and using the value read and the
		/// given codebook, rebuild LSP table.
		/// </summary>
		protected internal void UnpackPlus(float[] lsp, int[] tab, Bits bits, float k, int ti, int li)
		{
			int id = bits.Unpack(6);
			for (int i = 0; i < ti; i++)
				lsp[i + li] += k * (float)tab[id * ti + i];
		}

		/// <summary>
		/// LSP quantification Note: x is modified
		/// </summary>
		/// <returns>the index of the best match in the codebook (NB x is also</returns>
		protected static internal int Lsp_quant(float[] x, int xs, int[] cdbk, int nbVec, int nbDim)
		{
			int i, j;
			float dist, tmp;
			float best_dist = 0;
			int best_id = 0;
			int ptr = 0;
			for (i = 0; i < nbVec; i++)
			{
				dist = 0;
				for (j = 0; j < nbDim; j++)
				{
					tmp = (x[xs + j] - cdbk[ptr++]);
					dist += tmp * tmp;
				}
				if (dist < best_dist || i == 0)
				{
					best_dist = dist;
					best_id = i;
				}
			}

			for (j = 0; j < nbDim; j++)
				x[xs + j] -= cdbk[best_id * nbDim + j];

			return best_id;
		}

		/// <summary>
		/// LSP weighted quantification Note: x is modified
		/// </summary>
		/// <returns>the index of the best match in the codebook (NB x is also</returns>
		protected static internal int Lsp_weight_quant(
			float[] x, int xs,
			float[] weight, int ws, int[] cdbk,
			int nbVec, int nbDim)
		{
			int i, j;
			float dist, tmp;
			float best_dist = 0;
			int best_id = 0;
			int ptr = 0;
			for (i = 0; i < nbVec; i++)
			{
				dist = 0;
				for (j = 0; j < nbDim; j++)
				{
					tmp = (x[xs + j] - cdbk[ptr++]);
					dist += weight[ws + j] * tmp * tmp;
				}
				if (dist < best_dist || i == 0)
				{
					best_dist = dist;
					best_id = i;
				}
			}
			for (j = 0; j < nbDim; j++)
				x[xs + j] -= cdbk[best_id * nbDim + j];
			return best_id;
		}
	}
}