Statistics
| Branch: | Revision:

ffmpeg / libavcodec / 8svx.c @ 2912e87a

History | View | Annotate | Download (3.38 KB)

1
/*
2
 * 8SVX audio decoder
3
 * Copyright (C) 2008 Jaikrishnan Menon
4
 *
5
 * This file is part of Libav.
6
 *
7
 * Libav 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
 * Libav 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 Libav; 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
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 */
33
typedef struct EightSvxContext {
34
    int16_t fib_acc;
35
    const int16_t *table;
36
} EightSvxContext;
37

    
38
static 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 };
40
static 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 */
44
static int eightsvx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
45
                                 AVPacket *avpkt)
46
{
47
    const uint8_t *buf = avpkt->data;
48
    int buf_size = avpkt->size;
49
    EightSvxContext *esc = avctx->priv_data;
50
    int16_t *out_data = data;
51
    int consumed = buf_size;
52
    const uint8_t *buf_end = buf + buf_size;
53

    
54
    if((*data_size >> 2) < buf_size)
55
        return -1;
56

    
57
    if(avctx->frame_number == 0) {
58
        esc->fib_acc = buf[1] << 8;
59
        buf_size -= 2;
60
        buf += 2;
61
    }
62

    
63
    *data_size = buf_size << 2;
64

    
65
    while(buf < buf_end) {
66
        uint8_t d = *buf++;
67
        esc->fib_acc += esc->table[d & 0x0f];
68
        *out_data++ = esc->fib_acc;
69
        esc->fib_acc += esc->table[d >> 4];
70
        *out_data++ = esc->fib_acc;
71
    }
72

    
73
    return consumed;
74
}
75

    
76
/** initialize 8svx decoder */
77
static av_cold int eightsvx_decode_init(AVCodecContext *avctx)
78
{
79
    EightSvxContext *esc = avctx->priv_data;
80

    
81
    switch(avctx->codec->id) {
82
        case CODEC_ID_8SVX_FIB:
83
          esc->table = fibonacci;
84
          break;
85
        case CODEC_ID_8SVX_EXP:
86
          esc->table = exponential;
87
          break;
88
        default:
89
          return -1;
90
    }
91
    avctx->sample_fmt = AV_SAMPLE_FMT_S16;
92
    return 0;
93
}
94

    
95
AVCodec ff_eightsvx_fib_decoder = {
96
  .name           = "8svx_fib",
97
  .type           = AVMEDIA_TYPE_AUDIO,
98
  .id             = CODEC_ID_8SVX_FIB,
99
  .priv_data_size = sizeof (EightSvxContext),
100
  .init           = eightsvx_decode_init,
101
  .decode         = eightsvx_decode_frame,
102
  .long_name      = NULL_IF_CONFIG_SMALL("8SVX fibonacci"),
103
};
104

    
105
AVCodec ff_eightsvx_exp_decoder = {
106
  .name           = "8svx_exp",
107
  .type           = AVMEDIA_TYPE_AUDIO,
108
  .id             = CODEC_ID_8SVX_EXP,
109
  .priv_data_size = sizeof (EightSvxContext),
110
  .init           = eightsvx_decode_init,
111
  .decode         = eightsvx_decode_frame,
112
  .long_name      = NULL_IF_CONFIG_SMALL("8SVX exponential"),
113
};