PeerStreamer

/*

 * 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,

};