Statistics
| Branch: | Revision:

ffmpeg / libavcodec / libgsm.c @ 202aca67

History | View | Annotate | Download (4.45 KB)

1
/*
2
 * Interface to libgsm for gsm encoding/decoding
3
 * Copyright (c) 2005 Alban Bedel <albeu@free.fr>
4
 * Copyright (c) 2006, 2007 Michel Bardiaux <mbardiaux@mediaxim.be>
5
 *
6
 * This file is part of FFmpeg.
7
 *
8
 * FFmpeg is free software; you can redistribute it and/or
9
 * modify it under the terms of the GNU Lesser General Public
10
 * License as published by the Free Software Foundation; either
11
 * version 2.1 of the License, or (at your option) any later version.
12
 *
13
 * FFmpeg is distributed in the hope that it will be useful,
14
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16
 * Lesser General Public License for more details.
17
 *
18
 * You should have received a copy of the GNU Lesser General Public
19
 * License along with FFmpeg; if not, write to the Free Software
20
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21
 */
22

    
23
/**
24
 * @file libgsm.c
25
 * Interface to libgsm for gsm encoding/decoding
26
 */
27

    
28
// The idiosyncrasies of GSM-in-WAV are explained at http://kbs.cs.tu-berlin.de/~jutta/toast.html
29

    
30
#include "avcodec.h"
31
#include <gsm.h>
32

    
33
// gsm.h misses some essential constants
34
#define GSM_BLOCK_SIZE 33
35
#define GSM_MS_BLOCK_SIZE 65
36
#define GSM_FRAME_SIZE 160
37

    
38
static av_cold int libgsm_init(AVCodecContext *avctx) {
39
    if (avctx->channels > 1) {
40
        av_log(avctx, AV_LOG_ERROR, "Mono required for GSM, got %d channels\n",
41
               avctx->channels);
42
        return -1;
43
    }
44
    if (avctx->sample_rate != 8000) {
45
        av_log(avctx, AV_LOG_ERROR, "Sample rate 8000Hz required for GSM, got %dHz\n",
46
               avctx->sample_rate);
47
        return -1;
48
    }
49
    if (avctx->bit_rate != 13000 /* Official */ &&
50
        avctx->bit_rate != 13200 /* Very common */ &&
51
        avctx->bit_rate != 0 /* Unknown; a.o. mov does not set bitrate when decoding */ ) {
52
        av_log(avctx, AV_LOG_ERROR, "Bitrate 13000bps required for GSM, got %dbps\n",
53
               avctx->bit_rate);
54
        return -1;
55
    }
56

    
57
    avctx->priv_data = gsm_create();
58

    
59
    switch(avctx->codec_id) {
60
    case CODEC_ID_GSM:
61
        avctx->frame_size = GSM_FRAME_SIZE;
62
        avctx->block_align = GSM_BLOCK_SIZE;
63
        break;
64
    case CODEC_ID_GSM_MS: {
65
        int one = 1;
66
        gsm_option(avctx->priv_data, GSM_OPT_WAV49, &one);
67
        avctx->frame_size = 2*GSM_FRAME_SIZE;
68
        avctx->block_align = GSM_MS_BLOCK_SIZE;
69
        }
70
    }
71

    
72
    avctx->coded_frame= avcodec_alloc_frame();
73
    avctx->coded_frame->key_frame= 1;
74

    
75
    return 0;
76
}
77

    
78
static av_cold int libgsm_close(AVCodecContext *avctx) {
79
    gsm_destroy(avctx->priv_data);
80
    avctx->priv_data = NULL;
81
    return 0;
82
}
83

    
84
static int libgsm_encode_frame(AVCodecContext *avctx,
85
                               unsigned char *frame, int buf_size, void *data) {
86
    // we need a full block
87
    if(buf_size < avctx->block_align) return 0;
88

    
89
    switch(avctx->codec_id) {
90
    case CODEC_ID_GSM:
91
        gsm_encode(avctx->priv_data,data,frame);
92
        break;
93
    case CODEC_ID_GSM_MS:
94
        gsm_encode(avctx->priv_data,data,frame);
95
        gsm_encode(avctx->priv_data,((short*)data)+GSM_FRAME_SIZE,frame+32);
96
    }
97
    return avctx->block_align;
98
}
99

    
100

    
101
AVCodec libgsm_encoder = {
102
    "libgsm",
103
    CODEC_TYPE_AUDIO,
104
    CODEC_ID_GSM,
105
    0,
106
    libgsm_init,
107
    libgsm_encode_frame,
108
    libgsm_close,
109
};
110

    
111
AVCodec libgsm_ms_encoder = {
112
    "libgsm_ms",
113
    CODEC_TYPE_AUDIO,
114
    CODEC_ID_GSM_MS,
115
    0,
116
    libgsm_init,
117
    libgsm_encode_frame,
118
    libgsm_close,
119
};
120

    
121
static int libgsm_decode_frame(AVCodecContext *avctx,
122
                               void *data, int *data_size,
123
                               uint8_t *buf, int buf_size) {
124
    *data_size = 0; /* In case of error */
125
    if(buf_size < avctx->block_align) return -1;
126
    switch(avctx->codec_id) {
127
    case CODEC_ID_GSM:
128
        if(gsm_decode(avctx->priv_data,buf,data)) return -1;
129
        *data_size = GSM_FRAME_SIZE*sizeof(int16_t);
130
        break;
131
    case CODEC_ID_GSM_MS:
132
        if(gsm_decode(avctx->priv_data,buf,data) ||
133
           gsm_decode(avctx->priv_data,buf+33,((int16_t*)data)+GSM_FRAME_SIZE)) return -1;
134
        *data_size = GSM_FRAME_SIZE*sizeof(int16_t)*2;
135
    }
136
    return avctx->block_align;
137
}
138

    
139
AVCodec libgsm_decoder = {
140
    "libgsm",
141
    CODEC_TYPE_AUDIO,
142
    CODEC_ID_GSM,
143
    0,
144
    libgsm_init,
145
    NULL,
146
    libgsm_close,
147
    libgsm_decode_frame,
148
};
149

    
150
AVCodec libgsm_ms_decoder = {
151
    "libgsm_ms",
152
    CODEC_TYPE_AUDIO,
153
    CODEC_ID_GSM_MS,
154
    0,
155
    libgsm_init,
156
    NULL,
157
    libgsm_close,
158
    libgsm_decode_frame,
159
};