ref: 4b4241830d669436bff595a1deaa5148f9562d79
dir: /libfaad/common.c/
/* ** FAAD - Freeware Advanced Audio Decoder ** Copyright (C) 2002 M. Bakker ** ** This program is free software; you can redistribute it and/or modify ** it under the terms of the GNU General Public License as published by ** the Free Software Foundation; either version 2 of the License, or ** (at your option) any later version. ** ** This program is distributed in the hope that it will be useful, ** but WITHOUT ANY WARRANTY; without even the implied warranty of ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ** GNU General Public License for more details. ** ** You should have received a copy of the GNU General Public License ** along with this program; if not, write to the Free Software ** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. ** ** $Id: common.c,v 1.5 2002/11/28 18:48:29 menno Exp $ **/ /* just some common functions that could be used anywhere */ #include "common.h" #include "structs.h" #include "syntax.h" /* Returns the sample rate index based on the samplerate */ uint8_t get_sr_index(uint32_t samplerate) { if (92017 <= samplerate) return 0; if (75132 <= samplerate) return 1; if (55426 <= samplerate) return 2; if (46009 <= samplerate) return 3; if (37566 <= samplerate) return 4; if (27713 <= samplerate) return 5; if (23004 <= samplerate) return 6; if (18783 <= samplerate) return 7; if (13856 <= samplerate) return 8; if (11502 <= samplerate) return 9; if (9391 <= samplerate) return 10; return 11; } /* Returns 0 if an object type is decodable, otherwise returns -1 */ int8_t can_decode_ot(uint8_t object_type) { switch (object_type) { case LC: return 0; case MAIN: #ifdef MAIN_DEC return 0; #else return -1; #endif case SSR: #ifdef SSR_DEC return 0; #else return -1; #endif case LTP: #ifdef LTP_DEC return 0; #else return -1; #endif /* ER object types */ #ifdef ERROR_RESILIENCE case ER_LC: #ifdef DRM case DRM_ER_LC: #endif return 0; case ER_LTP: #ifdef LTP_DEC return 0; #else return -1; #endif case LD: #ifdef LD_DEC return 0; #else return -1; #endif #endif } return -1; } static const uint8_t Parity [256] = { // parity 0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1, 1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0, 1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0, 0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1, 1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0, 0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1, 0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1, 1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0 }; static uint32_t __r1 = 1; static uint32_t __r2 = 1; /* * This is a simple random number generator with good quality for audio purposes. * It consists of two polycounters with opposite rotation direction and different * periods. The periods are coprime, so the total period is the product of both. * * ------------------------------------------------------------------------------------------------- * +-> |31:30:29:28:27:26:25:24:23:22:21:20:19:18:17:16:15:14:13:12:11:10: 9: 8: 7: 6: 5: 4: 3: 2: 1: 0| * | ------------------------------------------------------------------------------------------------- * | | | | | | | * | +--+--+--+-XOR-+--------+ * | | * +--------------------------------------------------------------------------------------+ * * ------------------------------------------------------------------------------------------------- * |31:30:29:28:27:26:25:24:23:22:21:20:19:18:17:16:15:14:13:12:11:10: 9: 8: 7: 6: 5: 4: 3: 2: 1: 0| <-+ * ------------------------------------------------------------------------------------------------- | * | | | | | * +--+----XOR----+--+ | * | | * +----------------------------------------------------------------------------------------+ * * * The first has an period of 3*5*17*257*65537, the second of 7*47*73*178481, * which gives a period of 18.410.713.077.675.721.215. The result is the * XORed values of both generators. */ uint32_t random_int(void) { uint32_t t1, t2, t3, t4; t3 = t1 = __r1; t4 = t2 = __r2; // Parity calculation is done via table lookup, this is also available t1 &= 0xF5; t2 >>= 25; // on CPUs without parity, can be implemented in C and avoid unpredictable t1 = Parity [t1]; t2 &= 0x63; // jumps and slow rotate through the carry flag operations. t1 <<= 31; t2 = Parity [t2]; return (__r1 = (t3 >> 1) | t1 ) ^ (__r2 = (t4 + t4) | t2 ); } #if 0 #define LOG2 0.30102999566398 uint32_t int_log2(uint32_t val) { return (uint32_t)(log((real_t)val)/LOG2 + 0.5); } #endif