1/*
2 * 8SVX audio decoder
3 * Copyright (C) 2008 Jaikrishnan Menon
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22/**
23 * @file libavcodec/8svx.c
24 * 8svx audio decoder
25 * @author Jaikrishnan Menon
26 * supports: fibonacci delta encoding
27 *         : exponential encoding
28 */
29
30#include "avcodec.h"
31
32/** decoder context */
33typedef struct EightSvxContext {
34    int16_t fib_acc;
35    const int16_t *table;
36} EightSvxContext;
37
38static const int16_t fibonacci[16]   = { -34<<8, -21<<8, -13<<8,  -8<<8, -5<<8, -3<<8, -2<<8, -1<<8,
39                                          0, 1<<8, 2<<8, 3<<8, 5<<8, 8<<8, 13<<8, 21<<8 };
40static const int16_t exponential[16] = { -128<<8, -64<<8, -32<<8, -16<<8, -8<<8, -4<<8, -2<<8, -1<<8,
41                                          0, 1<<8, 2<<8, 4<<8, 8<<8, 16<<8, 32<<8, 64<<8 };
42
43/** decode a frame */
44static int eightsvx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
45                                 const uint8_t *buf, int buf_size)
46{
47    EightSvxContext *esc = avctx->priv_data;
48    int16_t *out_data = data;
49    int consumed = buf_size;
50    const uint8_t *buf_end = buf + buf_size;
51
52    if((*data_size >> 2) < buf_size)
53        return -1;
54
55    if(avctx->frame_number == 0) {
56        esc->fib_acc = buf[1] << 8;
57        buf_size -= 2;
58        buf += 2;
59    }
60
61    *data_size = buf_size << 2;
62
63    while(buf < buf_end) {
64        uint8_t d = *buf++;
65        esc->fib_acc += esc->table[d & 0x0f];
66        *out_data++ = esc->fib_acc;
67        esc->fib_acc += esc->table[d >> 4];
68        *out_data++ = esc->fib_acc;
69    }
70
71    return consumed;
72}
73
74/** initialize 8svx decoder */
75static av_cold int eightsvx_decode_init(AVCodecContext *avctx)
76{
77    EightSvxContext *esc = avctx->priv_data;
78
79    switch(avctx->codec->id) {
80        case CODEC_ID_8SVX_FIB:
81          esc->table = fibonacci;
82          break;
83        case CODEC_ID_8SVX_EXP:
84          esc->table = exponential;
85          break;
86        default:
87          return -1;
88    }
89    avctx->sample_fmt = SAMPLE_FMT_S16;
90    return 0;
91}
92
93AVCodec eightsvx_fib_decoder = {
94  .name           = "8svx_fib",
95  .type           = CODEC_TYPE_AUDIO,
96  .id             = CODEC_ID_8SVX_FIB,
97  .priv_data_size = sizeof (EightSvxContext),
98  .init           = eightsvx_decode_init,
99  .decode         = eightsvx_decode_frame,
100  .long_name      = NULL_IF_CONFIG_SMALL("8SVX fibonacci"),
101};
102
103AVCodec eightsvx_exp_decoder = {
104  .name           = "8svx_exp",
105  .type           = CODEC_TYPE_AUDIO,
106  .id             = CODEC_ID_8SVX_EXP,
107  .priv_data_size = sizeof (EightSvxContext),
108  .init           = eightsvx_decode_init,
109  .decode         = eightsvx_decode_frame,
110  .long_name      = NULL_IF_CONFIG_SMALL("8SVX exponential"),
111};
112