libavcodec/8svx.c

   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 8svx.c
  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 */
  33 typedef struct EightSvxContext {
  34     int16_t fib_acc;
  35     int16_t *table;
  36 } EightSvxContext;
  37
  38 const static 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 };
  40 const static 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 */
  44 static int eightsvx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
  45                                  const uint8_t *buf, int buf_size)
  46 {
  47     EightSvxContext *esc = avctx->priv_data;
  48     int16_t *out_data = data;
  49     int consumed = buf_size;
  50     const uint8_t *buf_end = buf + buf_size;
  51
  52     if((*data_size >> 2) < buf_size)
  53         return -1;
  54
  55     if(avctx->frame_number == 0) {
  56         esc->fib_acc = buf[1] << 8;
  57         buf_size -= 2;
  58         buf += 2;
  59     }
  60
  61     *data_size = buf_size << 2;
  62
  63     while(buf < buf_end) {
  64         uint8_t d = *buf++;
  65         esc->fib_acc += esc->table[d & 0x0f];
  66         *out_data++ = esc->fib_acc;
  67         esc->fib_acc += esc->table[d >> 4];
  68         *out_data++ = esc->fib_acc;
  69     }
  70
  71     return consumed;
  72 }
  73
  74 /** initialize 8svx decoder */
  75 static av_cold int eightsvx_decode_init(AVCodecContext *avctx)
  76 {
  77     EightSvxContext *esc = avctx->priv_data;
  78
  79     switch(avctx->codec->id) {
  80         case CODEC_ID_8SVX_FIB:
  81           esc->table = fibonacci;
  82           break;
  83         case CODEC_ID_8SVX_EXP:
  84           esc->table = exponential;
  85           break;
  86         default:
  87           return -1;
  88     }
  89     return 0;
  90 }
  91
  92 AVCodec eightsvx_fib_decoder = {
  93   .name           = "8svx_fib",
  94   .type           = CODEC_TYPE_AUDIO,
  95   .id             = CODEC_ID_8SVX_FIB,
  96   .priv_data_size = sizeof (EightSvxContext),
  97   .init           = eightsvx_decode_init,
  98   .decode         = eightsvx_decode_frame,
  99   .long_name      = "8SVX fibonacci",
 100 };
 101
 102 AVCodec eightsvx_exp_decoder = {
 103   .name           = "8svx_exp",
 104   .type           = CODEC_TYPE_AUDIO,
 105   .id             = CODEC_ID_8SVX_EXP,
 106   .priv_data_size = sizeof (EightSvxContext),
 107   .init           = eightsvx_decode_init,
 108   .decode         = eightsvx_decode_frame,
 109   .long_name      = "8SVX exponential",
 110 };