111 lines
3.3 KiB
C
111 lines
3.3 KiB
C
/*
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* 8SVX audio decoder
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* Copyright (C) 2008 Jaikrishnan Menon
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file 8svx.c
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* 8svx audio decoder
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* @author Jaikrishnan Menon
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* supports: fibonacci delta encoding
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* : exponential encoding
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*/
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#include "avcodec.h"
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/** decoder context */
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typedef struct EightSvxContext {
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int16_t fib_acc;
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int16_t *table;
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} EightSvxContext;
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const static int16_t fibonacci[16] = { -34<<8, -21<<8, -13<<8, -8<<8, -5<<8, -3<<8, -2<<8, -1<<8,
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0, 1<<8, 2<<8, 3<<8, 5<<8, 8<<8, 13<<8, 21<<8 };
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const static int16_t exponential[16] = { -128<<8, -64<<8, -32<<8, -16<<8, -8<<8, -4<<8, -2<<8, -1<<8,
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0, 1<<8, 2<<8, 4<<8, 8<<8, 16<<8, 32<<8, 64<<8 };
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/** decode a frame */
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static int eightsvx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
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const uint8_t *buf, int buf_size)
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{
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EightSvxContext *esc = avctx->priv_data;
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int16_t *out_data = data;
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int consumed = buf_size;
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const uint8_t *buf_end = buf + buf_size;
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if((*data_size >> 2) < buf_size)
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return -1;
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if(avctx->frame_number == 0) {
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esc->fib_acc = buf[1] << 8;
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buf_size -= 2;
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buf += 2;
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}
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*data_size = buf_size << 2;
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while(buf < buf_end) {
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uint8_t d = *buf++;
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esc->fib_acc += esc->table[d & 0x0f];
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*out_data++ = esc->fib_acc;
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esc->fib_acc += esc->table[d >> 4];
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*out_data++ = esc->fib_acc;
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}
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return consumed;
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}
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/** initialize 8svx decoder */
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static av_cold int eightsvx_decode_init(AVCodecContext *avctx)
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{
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EightSvxContext *esc = avctx->priv_data;
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switch(avctx->codec->id) {
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case CODEC_ID_8SVX_FIB:
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esc->table = fibonacci;
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break;
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case CODEC_ID_8SVX_EXP:
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esc->table = exponential;
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break;
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default:
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return -1;
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}
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return 0;
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}
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AVCodec eightsvx_fib_decoder = {
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.name = "8svx_fib",
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.type = CODEC_TYPE_AUDIO,
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.id = CODEC_ID_8SVX_FIB,
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.priv_data_size = sizeof (EightSvxContext),
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.init = eightsvx_decode_init,
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.decode = eightsvx_decode_frame,
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.long_name = NULL_IF_CONFIG_SMALL("8SVX fibonacci"),
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};
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AVCodec eightsvx_exp_decoder = {
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.name = "8svx_exp",
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.type = CODEC_TYPE_AUDIO,
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.id = CODEC_ID_8SVX_EXP,
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.priv_data_size = sizeof (EightSvxContext),
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.init = eightsvx_decode_init,
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.decode = eightsvx_decode_frame,
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.long_name = NULL_IF_CONFIG_SMALL("8SVX exponential"),
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};
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