Libav 0.7.1
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00001 /* 00002 * 8SVX audio decoder 00003 * Copyright (C) 2008 Jaikrishnan Menon 00004 * 00005 * This file is part of Libav. 00006 * 00007 * Libav is free software; you can redistribute it and/or 00008 * modify it under the terms of the GNU Lesser General Public 00009 * License as published by the Free Software Foundation; either 00010 * version 2.1 of the License, or (at your option) any later version. 00011 * 00012 * Libav is distributed in the hope that it will be useful, 00013 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00015 * Lesser General Public License for more details. 00016 * 00017 * You should have received a copy of the GNU Lesser General Public 00018 * License along with Libav; if not, write to the Free Software 00019 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00020 */ 00021 00030 #include "avcodec.h" 00031 00033 typedef struct EightSvxContext { 00034 int16_t fib_acc; 00035 const int16_t *table; 00036 } EightSvxContext; 00037 00038 static const int16_t fibonacci[16] = { -34<<8, -21<<8, -13<<8, -8<<8, -5<<8, -3<<8, -2<<8, -1<<8, 00039 0, 1<<8, 2<<8, 3<<8, 5<<8, 8<<8, 13<<8, 21<<8 }; 00040 static const int16_t exponential[16] = { -128<<8, -64<<8, -32<<8, -16<<8, -8<<8, -4<<8, -2<<8, -1<<8, 00041 0, 1<<8, 2<<8, 4<<8, 8<<8, 16<<8, 32<<8, 64<<8 }; 00042 00044 static int eightsvx_decode_frame(AVCodecContext *avctx, void *data, int *data_size, 00045 AVPacket *avpkt) 00046 { 00047 const uint8_t *buf = avpkt->data; 00048 int buf_size = avpkt->size; 00049 EightSvxContext *esc = avctx->priv_data; 00050 int16_t *out_data = data; 00051 int consumed = buf_size; 00052 const uint8_t *buf_end = buf + buf_size; 00053 00054 if((*data_size >> 2) < buf_size) 00055 return -1; 00056 00057 if(avctx->frame_number == 0) { 00058 esc->fib_acc = buf[1] << 8; 00059 buf_size -= 2; 00060 buf += 2; 00061 } 00062 00063 *data_size = buf_size << 2; 00064 00065 while(buf < buf_end) { 00066 uint8_t d = *buf++; 00067 esc->fib_acc += esc->table[d & 0x0f]; 00068 *out_data++ = esc->fib_acc; 00069 esc->fib_acc += esc->table[d >> 4]; 00070 *out_data++ = esc->fib_acc; 00071 } 00072 00073 return consumed; 00074 } 00075 00077 static av_cold int eightsvx_decode_init(AVCodecContext *avctx) 00078 { 00079 EightSvxContext *esc = avctx->priv_data; 00080 00081 switch(avctx->codec->id) { 00082 case CODEC_ID_8SVX_FIB: 00083 esc->table = fibonacci; 00084 break; 00085 case CODEC_ID_8SVX_EXP: 00086 esc->table = exponential; 00087 break; 00088 default: 00089 return -1; 00090 } 00091 avctx->sample_fmt = AV_SAMPLE_FMT_S16; 00092 return 0; 00093 } 00094 00095 AVCodec ff_eightsvx_fib_decoder = { 00096 .name = "8svx_fib", 00097 .type = AVMEDIA_TYPE_AUDIO, 00098 .id = CODEC_ID_8SVX_FIB, 00099 .priv_data_size = sizeof (EightSvxContext), 00100 .init = eightsvx_decode_init, 00101 .decode = eightsvx_decode_frame, 00102 .long_name = NULL_IF_CONFIG_SMALL("8SVX fibonacci"), 00103 }; 00104 00105 AVCodec ff_eightsvx_exp_decoder = { 00106 .name = "8svx_exp", 00107 .type = AVMEDIA_TYPE_AUDIO, 00108 .id = CODEC_ID_8SVX_EXP, 00109 .priv_data_size = sizeof (EightSvxContext), 00110 .init = eightsvx_decode_init, 00111 .decode = eightsvx_decode_frame, 00112 .long_name = NULL_IF_CONFIG_SMALL("8SVX exponential"), 00113 };