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/*
* 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.c
* 8svx audio decoder
* @author Jaikrishnan Menon
* supports: fibonacci delta encoding
* : exponential encoding
*/
#include "avcodec.h"
/**
* decoder context
*/
typedef struct EightSvxContext {
int16_t fib_acc;
int16_t *table;
} EightSvxContext;
const static 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 };
const static 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,
const uint8_t *buf, int buf_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;
}
return 0;
}
AVCodec eightsvx_fib_decoder = {
.name = "8svx fibonacci decoder",
.type = CODEC_TYPE_AUDIO,
.id = CODEC_ID_8SVX_FIB,
.priv_data_size = sizeof (EightSvxContext),
.init = eightsvx_decode_init,
.decode = eightsvx_decode_frame,
};
AVCodec eightsvx_exp_decoder = {
.name = "8svx exponential decoder",
.type = CODEC_TYPE_AUDIO,
.id = CODEC_ID_8SVX_EXP,
.priv_data_size = sizeof (EightSvxContext),
.init = eightsvx_decode_init,
.decode = eightsvx_decode_frame,
};
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