g722.h

Go to the documentation of this file.
00001 /*
00002  * SpanDSP - a series of DSP components for telephony
00003  *
00004  * g722.h - The ITU G.722 codec.
00005  *
00006  * Written by Steve Underwood <steveu@coppice.org>
00007  *
00008  * Copyright (C) 2005 Steve Underwood
00009  *
00010  * All rights reserved.
00011  *
00012  * This program is free software; you can redistribute it and/or modify
00013  * it under the terms of the GNU Lesser General Public License version 2.1,
00014  * as published by the Free Software Foundation.
00015  *
00016  * This program is distributed in the hope that it will be useful,
00017  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00018  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00019  * GNU Lesser General Public License for more details.
00020  *
00021  * You should have received a copy of the GNU Lesser General Public
00022  * License along with this program; if not, write to the Free Software
00023  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00024  *
00025  * Based on a single channel G.722 codec which is:
00026  *
00027  *****    Copyright (c) CMU    1993      *****
00028  * Computer Science, Speech Group
00029  * Chengxiang Lu and Alex Hauptmann
00030  *
00031  * $Id: g722.h,v 1.26 2009/04/12 09:12:10 steveu Exp $
00032  */
00033 
00034 
00035 /*! \file */
00036 
00037 #if !defined(_SPANDSP_G722_H_)
00038 #define _SPANDSP_G722_H_
00039 
00040 /*! \page g722_page G.722 encoding and decoding
00041 \section g722_page_sec_1 What does it do?
00042 The G.722 module is a bit exact implementation of the ITU G.722 specification for all three
00043 specified bit rates - 64000bps, 56000bps and 48000bps. It passes the ITU tests.
00044 
00045 To allow fast and flexible interworking with narrow band telephony, the encoder and decoder
00046 support an option for the linear audio to be an 8k samples/second stream. In this mode the
00047 codec is considerably faster, and still fully compatible with wideband terminals using G.722.
00048 
00049 \section g722_page_sec_2 How does it work?
00050 ???.
00051 */
00052 
00053 enum
00054 {
00055     G722_SAMPLE_RATE_8000 = 0x0001,
00056     G722_PACKED = 0x0002
00057 };
00058 
00059 /*!
00060     G.722 encode state
00061  */
00062 typedef struct g722_encode_state_s g722_encode_state_t;
00063 
00064 /*!
00065     G.722 decode state
00066  */
00067 typedef struct g722_decode_state_s g722_decode_state_t;
00068 
00069 #if defined(__cplusplus)
00070 extern "C"
00071 {
00072 #endif
00073 
00074 /*! Initialise an G.722 encode context.
00075     \param s The G.722 encode context.
00076     \param rate The required bit rate for the G.722 data.
00077            The valid rates are 64000, 56000 and 48000.
00078     \param options
00079     \return A pointer to the G.722 encode context, or NULL for error. */
00080 SPAN_DECLARE(g722_encode_state_t *) g722_encode_init(g722_encode_state_t *s, int rate, int options);
00081 
00082 /*! Release a G.722 encode context.
00083     \param s The G.722 encode context.
00084     \return 0 for OK. */
00085 SPAN_DECLARE(int) g722_encode_release(g722_encode_state_t *s);
00086 
00087 /*! Free a G.722 encode context.
00088     \param s The G.722 encode context.
00089     \return 0 for OK. */
00090 SPAN_DECLARE(int) g722_encode_free(g722_encode_state_t *s);
00091 
00092 /*! Encode a buffer of linear PCM data to G.722
00093     \param s The G.722 context.
00094     \param g722_data The G.722 data produced.
00095     \param amp The audio sample buffer.
00096     \param len The number of samples in the buffer.
00097     \return The number of bytes of G.722 data produced. */
00098 SPAN_DECLARE(int) g722_encode(g722_encode_state_t *s, uint8_t g722_data[], const int16_t amp[], int len);
00099 
00100 /*! Initialise an G.722 decode context.
00101     \param s The G.722 decode context.
00102     \param rate The bit rate of the G.722 data.
00103            The valid rates are 64000, 56000 and 48000.
00104     \param options
00105     \return A pointer to the G.722 decode context, or NULL for error. */
00106 SPAN_DECLARE(g722_decode_state_t *) g722_decode_init(g722_decode_state_t *s, int rate, int options);
00107 
00108 /*! Release a G.722 decode context.
00109     \param s The G.722 decode context.
00110     \return 0 for OK. */
00111 SPAN_DECLARE(int) g722_decode_release(g722_decode_state_t *s);
00112 
00113 /*! Free a G.722 decode context.
00114     \param s The G.722 decode context.
00115     \return 0 for OK. */
00116 SPAN_DECLARE(int) g722_decode_free(g722_decode_state_t *s);
00117 
00118 /*! Decode a buffer of G.722 data to linear PCM.
00119     \param s The G.722 context.
00120     \param amp The audio sample buffer.
00121     \param g722_data
00122     \param len
00123     \return The number of samples returned. */
00124 SPAN_DECLARE(int) g722_decode(g722_decode_state_t *s, int16_t amp[], const uint8_t g722_data[], int len);
00125 
00126 #if defined(__cplusplus)
00127 }
00128 #endif
00129 
00130 #endif

Generated by  doxygen 1.6.2