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libavcodec/8svx.c

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00001 /*
00002  * 8SVX audio decoder
00003  * Copyright (C) 2008 Jaikrishnan Menon
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg 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  * FFmpeg 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 FFmpeg; 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 = SAMPLE_FMT_S16;
00092     return 0;
00093 }
00094 
00095 AVCodec 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 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 };

Generated on Fri Sep 16 2011 17:17:32 for FFmpeg by  doxygen 1.7.1