spandsp: lpc10.h Source File

spandsp 0.0.6

lpc10.h
1/*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * lpc10.h - LPC10 low bit rate speech codec.
5 *
6 * Written by Steve Underwood <steveu@coppice.org>
7 *
8 * Copyright (C) 2006 Steve Underwood
9 *
10 * All rights reserved.
11 *
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Lesser General Public License version 2.1,
14 * as published by the Free Software Foundation.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU Lesser General Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser General Public
22 * License along with this program; if not, write to the Free Software
23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 */
25
26#if !defined(_SPANDSP_LPC10_H_)
27#define _SPANDSP_LPC10_H_
28
29/*! \page lpc10_page LPC10 encoding and decoding
30\section lpc10_page_sec_1 What does it do?
31The LPC10 module implements the US Department of Defense LPC10
32codec. This codec produces compressed data at 2400bps. At such
33a low rate high fidelity cannot be expected. However, the speech
34clarity is quite good, and this codec is unencumbered by patent
35or other restrictions.
36
37\section lpc10_page_sec_2 How does it work?
38???.
39*/
40
41#define LPC10_SAMPLES_PER_FRAME 180
42#define LPC10_BITS_IN_COMPRESSED_FRAME 54
43
44/*!
45 LPC10 codec unpacked frame.
46*/
47 typedef struct
48{
49 /*! Pitch */
50 int32_t ipitch;
51 /*! Energy */
52 int32_t irms;
53 /*! Reflection coefficients */
54 int32_t irc[10];
55} lpc10_frame_t;
56
57/*!
58 LPC10 codec encoder state descriptor. This defines the state of
59 a single working instance of the LPC10 encoder.
60*/
61typedef struct lpc10_encode_state_s lpc10_encode_state_t;
62
63/*!
64 LPC10 codec decoder state descriptor. This defines the state of
65 a single working instance of the LPC10 decoder.
66*/
67typedef struct lpc10_decode_state_s lpc10_decode_state_t;
68
69#if defined(__cplusplus)
70extern "C"
71{
72#endif
73
74/*! Initialise an LPC10e encode context.
75 \param s The LPC10e context
76 \param error_correction ???
77 \return A pointer to the LPC10e context, or NULL for error. */
78SPAN_DECLARE(lpc10_encode_state_t *) lpc10_encode_init(lpc10_encode_state_t *s, int error_correction);
79
80SPAN_DECLARE(int) lpc10_encode_release(lpc10_encode_state_t *s);
81
82SPAN_DECLARE(int) lpc10_encode_free(lpc10_encode_state_t *s);
83
84/*! Encode a buffer of linear PCM data to LPC10e.
85 \param s The LPC10e context.
86 \param ima_data The LPC10e data produced.
87 \param amp The audio sample buffer.
88 \param len The number of samples in the buffer. This must be a multiple of 180, as
89 this is the number of samples on a frame.
90 \return The number of bytes of LPC10e data produced. */
91SPAN_DECLARE(int) lpc10_encode(lpc10_encode_state_t *s, uint8_t code[], const int16_t amp[], int len);
92
93/*! Initialise an LPC10e decode context.
94 \param s The LPC10e context
95 \param error_correction ???
96 \return A pointer to the LPC10e context, or NULL for error. */
97SPAN_DECLARE(lpc10_decode_state_t *) lpc10_decode_init(lpc10_decode_state_t *st, int error_correction);
98
99SPAN_DECLARE(int) lpc10_decode_release(lpc10_decode_state_t *s);
100
101SPAN_DECLARE(int) lpc10_decode_free(lpc10_decode_state_t *s);
102
103/*! Decode a buffer of LPC10e data to linear PCM.
104 \param s The LPC10e context.
105 \param amp The audio sample buffer.
106 \param code The LPC10e data.
107 \param len The number of bytes of LPC10e data to be decoded. This must be a multiple of 7,
108 as each frame is packed into 7 bytes.
109 \return The number of samples returned. */
110SPAN_DECLARE(int) lpc10_decode(lpc10_decode_state_t *s, int16_t amp[], const uint8_t code[], int len);
111
112
113#if defined(__cplusplus)
114}
115#endif
116
117#endif
118/*- End of include ---------------------------------------------------------*/
lpc10_decode_state_s
Definition private/lpc10.h:144
lpc10_decode_state_s::error_correction
int error_correction
???
Definition private/lpc10.h:146
lpc10_encode_state_s
Definition private/lpc10.h:34
lpc10_frame_t
Definition lpc10.h:48
lpc10_frame_t::ipitch
int32_t ipitch
Definition lpc10.h:50
lpc10_frame_t::irms
int32_t irms
Definition lpc10.h:52