g722.h

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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 1.22 2008/10/13 13:14:00 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 typedef struct g722_encode_state_s g722_encode_state_t;
00060 
00061 typedef struct g722_decode_state_s g722_decode_state_t;
00062 
00063 #if defined(__cplusplus)
00064 extern "C"
00065 {
00066 #endif
00067 
00068 /*! Initialise an G.722 encode context.
00069     \param s The G.722 encode context.
00070     \param rate The required bit rate for the G.722 data.
00071            The valid rates are 64000, 56000 and 48000.
00072     \param options
00073     \return A pointer to the G.722 encode context, or NULL for error. */
00074 g722_encode_state_t *g722_encode_init(g722_encode_state_t *s, int rate, int options);
00075 
00076 int g722_encode_release(g722_encode_state_t *s);
00077 
00078 /*! Encode a buffer of linear PCM data to G.722
00079     \param s The G.722 context.
00080     \param g722_data The G.722 data produced.
00081     \param amp The audio sample buffer.
00082     \param len The number of samples in the buffer.
00083     \return The number of bytes of G.722 data produced. */
00084 int g722_encode(g722_encode_state_t *s, uint8_t g722_data[], const int16_t amp[], int len);
00085 
00086 /*! Initialise an G.722 decode context.
00087     \param s The G.722 decode context.
00088     \param rate The bit rate of the G.722 data.
00089            The valid rates are 64000, 56000 and 48000.
00090     \param options
00091     \return A pointer to the G.722 decode context, or NULL for error. */
00092 g722_decode_state_t *g722_decode_init(g722_decode_state_t *s, int rate, int options);
00093 
00094 int g722_decode_release(g722_decode_state_t *s);
00095 
00096 /*! Decode a buffer of G.722 data to linear PCM.
00097     \param s The G.722 context.
00098     \param amp The audio sample buffer.
00099     \param g722_data
00100     \param len
00101     \return The number of samples returned. */
00102 int g722_decode(g722_decode_state_t *s, int16_t amp[], const uint8_t g722_data[], int len);
00103 
00104 #if defined(__cplusplus)
00105 }
00106 #endif
00107 
00108 #endif

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