PeerStreamer

/*

 * 8SVX audio decoder

 * Copyright (C) 2008 Jaikrishnan Menon

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg 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 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg 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 FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

/**

 * @file

 * 8svx audio decoder

 * @author Jaikrishnan Menon

 * supports: fibonacci delta encoding

 *         : exponential encoding

 */

#include "avcodec.h"

/** decoder context */

typedef struct EightSvxContext {

    int16_t fib_acc;

    const int16_t *table;

} EightSvxContext;

static const int16_t fibonacci[16]   = { -34<<8, -21<<8, -13<<8,  -8<<8, -5<<8, -3<<8, -2<<8, -1<<8,

                                          0, 1<<8, 2<<8, 3<<8, 5<<8, 8<<8, 13<<8, 21<<8 };

static const int16_t exponential[16] = { -128<<8, -64<<8, -32<<8, -16<<8, -8<<8, -4<<8, -2<<8, -1<<8,

                                          0, 1<<8, 2<<8, 4<<8, 8<<8, 16<<8, 32<<8, 64<<8 };

/** decode a frame */

static int eightsvx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,

                                 AVPacket *avpkt)

{

    const uint8_t *buf = avpkt->data;

    int buf_size = avpkt->size;

    EightSvxContext *esc = avctx->priv_data;

    int16_t *out_data = data;

    int consumed = buf_size;

    const uint8_t *buf_end = buf + buf_size;

    if((*data_size >> 2) < buf_size)

        return -1;

    if(avctx->frame_number == 0) {

        esc->fib_acc = buf[1] << 8;

        buf_size -= 2;

        buf += 2;

    }

    *data_size = buf_size << 2;

    while(buf < buf_end) {

        uint8_t d = *buf++;

        esc->fib_acc += esc->table[d & 0x0f];

        *out_data++ = esc->fib_acc;

        esc->fib_acc += esc->table[d >> 4];

        *out_data++ = esc->fib_acc;

    }

    return consumed;

}

/** initialize 8svx decoder */

static av_cold int eightsvx_decode_init(AVCodecContext *avctx)

{

    EightSvxContext *esc = avctx->priv_data;

    switch(avctx->codec->id) {

        case CODEC_ID_8SVX_FIB:

          esc->table = fibonacci;

          break;

        case CODEC_ID_8SVX_EXP:

          esc->table = exponential;

          break;

        default:

          return -1;

    }

    avctx->sample_fmt = AV_SAMPLE_FMT_S16;

    return 0;

}

AVCodec ff_eightsvx_fib_decoder = {

  .name           = "8svx_fib",

  .type           = AVMEDIA_TYPE_AUDIO,

  .id             = CODEC_ID_8SVX_FIB,

  .priv_data_size = sizeof (EightSvxContext),

  .init           = eightsvx_decode_init,

  .decode         = eightsvx_decode_frame,

  .long_name      = NULL_IF_CONFIG_SMALL("8SVX fibonacci"),

};

AVCodec ff_eightsvx_exp_decoder = {

  .name           = "8svx_exp",

  .type           = AVMEDIA_TYPE_AUDIO,

  .id             = CODEC_ID_8SVX_EXP,

  .priv_data_size = sizeof (EightSvxContext),

  .init           = eightsvx_decode_init,

  .decode         = eightsvx_decode_frame,

  .long_name      = NULL_IF_CONFIG_SMALL("8SVX exponential"),

};