1/* 2 * 8SVX audio decoder 3 * Copyright (C) 2008 Jaikrishnan Menon 4 * 5 * This file is part of FFmpeg. 6 * 7 * FFmpeg is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * FFmpeg is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with FFmpeg; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21 22/** 23 * @file 24 * 8svx audio decoder 25 * @author Jaikrishnan Menon 26 * supports: fibonacci delta encoding 27 * : exponential encoding 28 */ 29 30#include "avcodec.h" 31 32/** decoder context */ 33typedef struct EightSvxContext { 34 int16_t fib_acc; 35 const int16_t *table; 36} EightSvxContext; 37 38static const int16_t fibonacci[16] = { -34<<8, -21<<8, -13<<8, -8<<8, -5<<8, -3<<8, -2<<8, -1<<8, 39 0, 1<<8, 2<<8, 3<<8, 5<<8, 8<<8, 13<<8, 21<<8 }; 40static const int16_t exponential[16] = { -128<<8, -64<<8, -32<<8, -16<<8, -8<<8, -4<<8, -2<<8, -1<<8, 41 0, 1<<8, 2<<8, 4<<8, 8<<8, 16<<8, 32<<8, 64<<8 }; 42 43/** decode a frame */ 44static int eightsvx_decode_frame(AVCodecContext *avctx, void *data, int *data_size, 45 AVPacket *avpkt) 46{ 47 const uint8_t *buf = avpkt->data; 48 int buf_size = avpkt->size; 49 EightSvxContext *esc = avctx->priv_data; 50 int16_t *out_data = data; 51 int consumed = buf_size; 52 const uint8_t *buf_end = buf + buf_size; 53 54 if((*data_size >> 2) < buf_size) 55 return -1; 56 57 if(avctx->frame_number == 0) { 58 esc->fib_acc = buf[1] << 8; 59 buf_size -= 2; 60 buf += 2; 61 } 62 63 *data_size = buf_size << 2; 64 65 while(buf < buf_end) { 66 uint8_t d = *buf++; 67 esc->fib_acc += esc->table[d & 0x0f]; 68 *out_data++ = esc->fib_acc; 69 esc->fib_acc += esc->table[d >> 4]; 70 *out_data++ = esc->fib_acc; 71 } 72 73 return consumed; 74} 75 76/** initialize 8svx decoder */ 77static av_cold int eightsvx_decode_init(AVCodecContext *avctx) 78{ 79 EightSvxContext *esc = avctx->priv_data; 80 81 switch(avctx->codec->id) { 82 case CODEC_ID_8SVX_FIB: 83 esc->table = fibonacci; 84 break; 85 case CODEC_ID_8SVX_EXP: 86 esc->table = exponential; 87 break; 88 default: 89 return -1; 90 } 91 avctx->sample_fmt = SAMPLE_FMT_S16; 92 return 0; 93} 94 95AVCodec eightsvx_fib_decoder = { 96 .name = "8svx_fib", 97 .type = AVMEDIA_TYPE_AUDIO, 98 .id = CODEC_ID_8SVX_FIB, 99 .priv_data_size = sizeof (EightSvxContext), 100 .init = eightsvx_decode_init, 101 .decode = eightsvx_decode_frame, 102 .long_name = NULL_IF_CONFIG_SMALL("8SVX fibonacci"), 103}; 104 105AVCodec eightsvx_exp_decoder = { 106 .name = "8svx_exp", 107 .type = AVMEDIA_TYPE_AUDIO, 108 .id = CODEC_ID_8SVX_EXP, 109 .priv_data_size = sizeof (EightSvxContext), 110 .init = eightsvx_decode_init, 111 .decode = eightsvx_decode_frame, 112 .long_name = NULL_IF_CONFIG_SMALL("8SVX exponential"), 113}; 114