--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.3/spandsp-0.0.3/src/spandsp/g726.h	Fri Jun 25 16:00:21 2010 +0200
@@ -0,0 +1,191 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * g726.h - ITU G.726 codec.
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2006 Steve Underwood
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program 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
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * Based on G.721/G.723 code which is:
+ *
+ * This source code is a product of Sun Microsystems, Inc. and is provided
+ * for unrestricted use.  Users may copy or modify this source code without
+ * charge.
+ *
+ * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
+ * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
+ *
+ * Sun source code is provided with no support and without any obligation on
+ * the part of Sun Microsystems, Inc. to assist in its use, correction,
+ * modification or enhancement.
+ *
+ * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
+ * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
+ * OR ANY PART THEREOF.
+ *
+ * In no event will Sun Microsystems, Inc. be liable for any lost revenue
+ * or profits or other special, indirect and consequential damages, even if
+ * Sun has been advised of the possibility of such damages.
+ *
+ * Sun Microsystems, Inc.
+ * 2550 Garcia Avenue
+ * Mountain View, California  94043
+ *
+ * $Id: g726.h,v 1.13 2006/11/28 16:59:57 steveu Exp $
+ */
+
+/*! \file */
+
+#if !defined(_G726_H_)
+#define _G726_H_
+
+/*! \page g726_page G.726 encoding and decoding
+\section g726_page_sec_1 What does it do?
+
+The G.726 module is a bit exact implementation of the full ITU G.726 specification.
+It supports:
+    - 16 kbps, 24kbps, 32kbps, and 40kbps operation.
+    - Tandem adjustment, for interworking with A-law and u-law.
+    - Annex A support, for use in environments not using A-law or u-law.
+
+It passes the ITU tests.
+
+\section g726_page_sec_2 How does it work?
+???.
+*/
+
+enum
+{
+    G726_ENCODING_LINEAR = 0,   /* Interworking with 16 bit signed linear */
+    G726_ENCODING_ULAW,         /* Interworking with u-law */
+    G726_ENCODING_ALAW          /* Interworking with A-law */
+};
+
+enum
+{
+    G726_PACKING_NONE = 0,
+    G726_PACKING_LEFT = 1,
+    G726_PACKING_RIGHT = 2
+};
+
+struct g726_state_s;
+
+typedef int16_t (*g726_decoder_func_t)(struct g726_state_s *s, uint8_t code);
+
+typedef uint8_t (*g726_encoder_func_t)(struct g726_state_s *s, int16_t amp);
+
+/*
+ * The following is the definition of the state structure
+ * used by the G.726 encoder and decoder to preserve their internal
+ * state between successive calls.  The meanings of the majority
+ * of the state structure fields are explained in detail in the
+ * CCITT Recommendation G.721.  The field names are essentially indentical
+ * to variable names in the bit level description of the coding algorithm
+ * included in this Recommendation.
+ */
+typedef struct g726_state_s
+{
+    /*! The bit rate */
+    int rate;
+    /*! The external coding, for tandem operation */
+    int ext_coding;
+    /*! The number of bits per sample */
+    unsigned int bits_per_sample;
+    /*! One fo the G.726_PACKING_xxx options */
+    int packing;
+
+    /*! Locked or steady state step size multiplier. */
+    int32_t yl;
+    /*! Unlocked or non-steady state step size multiplier. */
+    int16_t yu;
+    /*! int16_t term energy estimate. */
+    int16_t dms;
+    /*! Long term energy estimate. */
+    int16_t dml;
+    /*! Linear weighting coefficient of 'yl' and 'yu'. */
+    int16_t ap;
+    
+    /*! Coefficients of pole portion of prediction filter. */
+    int16_t a[2];
+    /*! Coefficients of zero portion of prediction filter. */
+    int16_t b[6];
+    /*! Signs of previous two samples of a partially reconstructed signal. */
+    int16_t pk[2];
+    /*! Previous 6 samples of the quantized difference signal represented in
+        an internal floating point format. */
+    int16_t dq[6];
+    /*! Previous 2 samples of the quantized difference signal represented in an
+        internal floating point format. */
+    int16_t sr[2];
+    /*! Delayed tone detect */
+    int td;
+    
+    bitstream_state_t bs;
+
+    g726_encoder_func_t enc_func;
+    g726_decoder_func_t dec_func;
+} g726_state_t;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*! Initialise a G.726 encode or decode context.
+    \param s The G.726 context.
+    \param bit_rate The required bit rate for the ADPCM data.
+           The valid rates are 16000, 24000, 32000 and 40000.
+    \param ext_coding The coding used outside G.726.
+    \param packing One of the G.726_PACKING_xxx options.
+    \return A pointer to the G.726 context, or NULL for error. */
+g726_state_t *g726_init(g726_state_t *s, int bit_rate, int ext_coding, int packing);
+
+/*! Free a G.726 encode or decode context.
+    \param s The G.726 context.
+    \return 0 for OK. */
+int g726_release(g726_state_t *s);
+
+/*! Decode a buffer of G.726 ADPCM data to linear PCM, a-law or u-law.
+    \param s The G.726 context.
+    \param amp The audio sample buffer.
+    \param g726_data
+    \param g726_bytes
+    \return The number of samples returned. */
+int g726_decode(g726_state_t *s,
+                int16_t amp[],
+                const uint8_t g726_data[],
+                int g726_bytes);
+
+/*! Encode a buffer of linear PCM data to G.726 ADPCM.
+    \param s The G.726 context.
+    \param g726_data The G.726 data produced.
+    \param amp The audio sample buffer.
+    \param len The number of samples in the buffer.
+    \return The number of bytes of G.726 data produced. */
+int g726_encode(g726_state_t *s,
+                uint8_t g726_data[],
+                const int16_t amp[],
+                int len);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+/*- End of file ------------------------------------------------------------*/