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/*
* Interface to libgsm for gsm encoding/decoding
* Copyright (c) 2005 Alban Bedel <albeu@free.fr>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file libgsm.c
* Interface to libgsm for gsm encoding/decoding
*/
#include "avcodec.h"
#include <gsm.h>
// gsm.h miss some essential constants
#define GSM_BLOCK_SIZE 33
#define GSM_FRAME_SIZE 160
static int libgsm_init(AVCodecContext *avctx) {
if (avctx->channels > 1 || avctx->sample_rate != 8000)
return -1;
avctx->frame_size = GSM_FRAME_SIZE;
avctx->block_align = GSM_BLOCK_SIZE;
avctx->priv_data = gsm_create();
avctx->coded_frame= avcodec_alloc_frame();
avctx->coded_frame->key_frame= 1;
return 0;
}
static int libgsm_close(AVCodecContext *avctx) {
gsm_destroy(avctx->priv_data);
avctx->priv_data = NULL;
return 0;
}
static int libgsm_encode_frame(AVCodecContext *avctx,
unsigned char *frame, int buf_size, void *data) {
// we need a full block
if(buf_size < GSM_BLOCK_SIZE) return 0;
gsm_encode(avctx->priv_data,data,frame);
return GSM_BLOCK_SIZE;
}
AVCodec libgsm_encoder = {
"gsm",
CODEC_TYPE_AUDIO,
CODEC_ID_GSM,
0,
libgsm_init,
libgsm_encode_frame,
libgsm_close,
};
static int libgsm_decode_frame(AVCodecContext *avctx,
void *data, int *data_size,
uint8_t *buf, int buf_size) {
if(buf_size < GSM_BLOCK_SIZE) return 0;
if(gsm_decode(avctx->priv_data,buf,data)) return -1;
*data_size = GSM_FRAME_SIZE*2;
return GSM_BLOCK_SIZE;
}
AVCodec libgsm_decoder = {
"gsm",
CODEC_TYPE_AUDIO,
CODEC_ID_GSM,
0,
libgsm_init,
NULL,
libgsm_close,
libgsm_decode_frame,
};
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