libavcodec/libgsm.c

   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 int libgsm_init(AVCodecContext *avctx) {
  39     if (avctx->channels > 1 || avctx->sample_rate != 8000 || avctx->bit_rate != 13000)
  40         return -1;
  41
  42     avctx->priv_data = gsm_create();
  43
  44     switch(avctx->codec_id) {
  45     case CODEC_ID_GSM:
  46         avctx->frame_size = GSM_FRAME_SIZE;
  47         avctx->block_align = GSM_BLOCK_SIZE;
  48         break;
  49     case CODEC_ID_GSM_MS: {
  50         int one = 1;
  51         gsm_option(avctx->priv_data, GSM_OPT_WAV49, &one);
  52         avctx->frame_size = 2*GSM_FRAME_SIZE;
  53         avctx->block_align = GSM_MS_BLOCK_SIZE;
  54         }
  55     }
  56
  57     avctx->coded_frame= avcodec_alloc_frame();
  58     avctx->coded_frame->key_frame= 1;
  59
  60     return 0;
  61 }
  62
  63 static int libgsm_close(AVCodecContext *avctx) {
  64     gsm_destroy(avctx->priv_data);
  65     avctx->priv_data = NULL;
  66     return 0;
  67 }
  68
  69 static int libgsm_encode_frame(AVCodecContext *avctx,
  70                                unsigned char *frame, int buf_size, void *data) {
  71     // we need a full block
  72     if(buf_size < avctx->block_align) return 0;
  73
  74     switch(avctx->codec_id) {
  75     case CODEC_ID_GSM:
  76         gsm_encode(avctx->priv_data,data,frame);
  77         break;
  78     case CODEC_ID_GSM_MS:
  79         gsm_encode(avctx->priv_data,data,frame);
  80         gsm_encode(avctx->priv_data,((short*)data)+GSM_FRAME_SIZE,frame+32);
  81     }
  82     return avctx->block_align;
  83 }
  84
  85
  86 AVCodec libgsm_encoder = {
  87     "libgsm",
  88     CODEC_TYPE_AUDIO,
  89     CODEC_ID_GSM,
  90     0,
  91     libgsm_init,
  92     libgsm_encode_frame,
  93     libgsm_close,
  94 };
  95
  96 AVCodec libgsm_ms_encoder = {
  97     "libgsm_ms",
  98     CODEC_TYPE_AUDIO,
  99     CODEC_ID_GSM_MS,
 100     0,
 101     libgsm_init,
 102     libgsm_encode_frame,
 103     libgsm_close,
 104 };
 105
 106 static int libgsm_decode_frame(AVCodecContext *avctx,
 107                                void *data, int *data_size,
 108                                uint8_t *buf, int buf_size) {
 109
 110     if(buf_size < avctx->block_align) return 0;
 111
 112     switch(avctx->codec_id) {
 113     case CODEC_ID_GSM:
 114         if(gsm_decode(avctx->priv_data,buf,data)) return -1;
 115         *data_size = GSM_FRAME_SIZE*sizeof(int16_t);
 116         break;
 117     case CODEC_ID_GSM_MS:
 118         if(gsm_decode(avctx->priv_data,buf,data) ||
 119            gsm_decode(avctx->priv_data,buf+33,((int16_t*)data)+GSM_FRAME_SIZE)) return -1;
 120         *data_size = GSM_FRAME_SIZE*sizeof(int16_t)*2;
 121     }
 122     return avctx->block_align;
 123 }
 124
 125 AVCodec libgsm_decoder = {
 126     "libgsm",
 127     CODEC_TYPE_AUDIO,
 128     CODEC_ID_GSM,
 129     0,
 130     libgsm_init,
 131     NULL,
 132     libgsm_close,
 133     libgsm_decode_frame,
 134 };
 135
 136 AVCodec libgsm_ms_decoder = {
 137     "libgsm_ms",
 138     CODEC_TYPE_AUDIO,
 139     CODEC_ID_GSM_MS,
 140     0,
 141     libgsm_init,
 142     NULL,
 143     libgsm_close,
 144     libgsm_decode_frame,
 145 };