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libgsmdec.c
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1 /*
2  * Interface to libgsm for GSM 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
25  * Interface to libgsm for GSM 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 "config.h"
31 #if HAVE_GSM_H
32 #include <gsm.h>
33 #else
34 #include <gsm/gsm.h>
35 #endif
36 
38 #include "libavutil/common.h"
39 
40 #include "avcodec.h"
41 #include "internal.h"
42 #include "gsm.h"
43 
44 typedef struct LibGSMDecodeContext {
45  struct gsm_state *state;
47 
50 
51  avctx->channels = 1;
53  if (!avctx->sample_rate)
54  avctx->sample_rate = 8000;
56 
57  s->state = gsm_create();
58 
59  switch(avctx->codec_id) {
60  case AV_CODEC_ID_GSM:
61  avctx->frame_size = GSM_FRAME_SIZE;
62  avctx->block_align = GSM_BLOCK_SIZE;
63  break;
64  case AV_CODEC_ID_GSM_MS: {
65  int one = 1;
66  gsm_option(s->state, GSM_OPT_WAV49, &one);
67  avctx->frame_size = 2 * GSM_FRAME_SIZE;
69  }
70  }
71 
72  return 0;
73 }
74 
77 
78  gsm_destroy(s->state);
79  s->state = NULL;
80  return 0;
81 }
82 
83 static int libgsm_decode_frame(AVCodecContext *avctx, void *data,
84  int *got_frame_ptr, AVPacket *avpkt)
85 {
86  int i, ret;
88  AVFrame *frame = data;
89  uint8_t *buf = avpkt->data;
90  int buf_size = avpkt->size;
91  int16_t *samples;
92 
93  if (buf_size < avctx->block_align) {
94  av_log(avctx, AV_LOG_ERROR, "Packet is too small\n");
95  return AVERROR_INVALIDDATA;
96  }
97 
98  /* get output buffer */
99  frame->nb_samples = avctx->frame_size;
100  if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
101  return ret;
102  samples = (int16_t *)frame->data[0];
103 
104  for (i = 0; i < avctx->frame_size / GSM_FRAME_SIZE; i++) {
105  if ((ret = gsm_decode(s->state, buf, samples)) < 0)
106  return -1;
107  buf += GSM_BLOCK_SIZE;
108  samples += GSM_FRAME_SIZE;
109  }
110 
111  *got_frame_ptr = 1;
112 
113  return avctx->block_align;
114 }
115 
116 static void libgsm_flush(AVCodecContext *avctx) {
117  LibGSMDecodeContext *s = avctx->priv_data;
118  int one = 1;
119 
120  gsm_destroy(s->state);
121  s->state = gsm_create();
122  if (avctx->codec_id == AV_CODEC_ID_GSM_MS)
123  gsm_option(s->state, GSM_OPT_WAV49, &one);
124 }
125 
126 #if CONFIG_LIBGSM_DECODER
127 AVCodec ff_libgsm_decoder = {
128  .name = "libgsm",
129  .long_name = NULL_IF_CONFIG_SMALL("libgsm GSM"),
130  .type = AVMEDIA_TYPE_AUDIO,
131  .id = AV_CODEC_ID_GSM,
132  .priv_data_size = sizeof(LibGSMDecodeContext),
134  .close = libgsm_decode_close,
136  .flush = libgsm_flush,
137  .capabilities = CODEC_CAP_DR1,
138 };
139 #endif
140 #if CONFIG_LIBGSM_MS_DECODER
141 AVCodec ff_libgsm_ms_decoder = {
142  .name = "libgsm_ms",
143  .long_name = NULL_IF_CONFIG_SMALL("libgsm GSM Microsoft variant"),
144  .type = AVMEDIA_TYPE_AUDIO,
145  .id = AV_CODEC_ID_GSM_MS,
146  .priv_data_size = sizeof(LibGSMDecodeContext),
148  .close = libgsm_decode_close,
150  .flush = libgsm_flush,
151  .capabilities = CODEC_CAP_DR1,
152 };
153 #endif