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extract random utils to their own file util/random.[ch]

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they'll be used for decoding too, probably.

Change-Id: Id9cbb250c74fc0e876d4ea46b1b3dbf8356d6725
This commit is contained in:
Pascal Massimino
2013-10-30 02:00:33 -07:00
parent d3408720d8
commit 98aa33cf1e
7 changed files with 118 additions and 51 deletions
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2
src/utils/Makefile.am
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@ -23,6 +23,8 @@ COMMON_SOURCES += quant_levels_dec.c
COMMON_SOURCES += quant_levels_dec.h
COMMON_SOURCES += rescaler.c
COMMON_SOURCES += rescaler.h
COMMON_SOURCES += random.c
COMMON_SOURCES += random.h
COMMON_SOURCES += thread.c
COMMON_SOURCES += thread.h
COMMON_SOURCES += utils.c

50
src/utils/random.c Normal file
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@ -0,0 +1,50 @@
// Copyright 2013 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// Pseudo-random utilities
//
// Author: Skal (pascal.massimino@gmail.com)
#include <string.h>
#include "./random.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
//------------------------------------------------------------------------------
// 31b-range values
static const uint32_t kRandomTable[VP8_RANDOM_TABLE_SIZE] = {
0x0de15230, 0x03b31886, 0x775faccb, 0x1c88626a, 0x68385c55, 0x14b3b828,
0x4a85fef8, 0x49ddb84b, 0x64fcf397, 0x5c550289, 0x4a290000, 0x0d7ec1da,
0x5940b7ab, 0x5492577d, 0x4e19ca72, 0x38d38c69, 0x0c01ee65, 0x32a1755f,
0x5437f652, 0x5abb2c32, 0x0faa57b1, 0x73f533e7, 0x685feeda, 0x7563cce2,
0x6e990e83, 0x4730a7ed, 0x4fc0d9c6, 0x496b153c, 0x4f1403fa, 0x541afb0c,
0x73990b32, 0x26d7cb1c, 0x6fcc3706, 0x2cbb77d8, 0x75762f2a, 0x6425ccdd,
0x24b35461, 0x0a7d8715, 0x220414a8, 0x141ebf67, 0x56b41583, 0x73e502e3,
0x44cab16f, 0x28264d42, 0x73baaefb, 0x0a50ebed, 0x1d6ab6fb, 0x0d3ad40b,
0x35db3b68, 0x2b081e83, 0x77ce6b95, 0x5181e5f0, 0x78853bbc, 0x009f9494,
0x27e5ed3c
};
void VP8InitRandom(VP8Random* const rg, float dithering) {
memcpy(rg->tab_, kRandomTable, sizeof(rg->tab_));
rg->index1_ = 0;
rg->index2_ = 31;
rg->amp_ = (dithering < 0.0) ? 0
: (dithering > 1.0) ? (1 << VP8_RANDOM_DITHER_FIX)
: (uint32_t)((1 << VP8_RANDOM_DITHER_FIX) * dithering);
}
//------------------------------------------------------------------------------
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"
#endif

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src/utils/random.h Normal file
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@ -0,0 +1,56 @@
// Copyright 2013 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// Pseudo-random utilities
//
// Author: Skal (pascal.massimino@gmail.com)
#ifndef WEBP_UTILS_RANDOM_H_
#define WEBP_UTILS_RANDOM_H_
#include <assert.h>
#include "../webp/types.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
#define VP8_RANDOM_DITHER_FIX 8 // fixed-point precision for dithering
#define VP8_RANDOM_TABLE_SIZE 55
typedef struct {
int index1_, index2_;
uint32_t tab_[VP8_RANDOM_TABLE_SIZE];
int amp_;
} VP8Random;
// Initializes random generator with an amplitude 'dithering' in range [0..1].
extern void VP8InitRandom(VP8Random* const rg, float dithering);
// Returns a centered pseudo-random number with 'num_bits' amplitude.
// (uses D.Knuth's Difference-based random generator)
static WEBP_INLINE int VP8RandomBits(VP8Random* const rg, int num_bits) {
int diff;
assert(num_bits + VP8_RANDOM_DITHER_FIX <= 31);
diff = rg->tab_[rg->index1_] - rg->tab_[rg->index2_];
if (diff < 0) diff += (1u << 31);
rg->tab_[rg->index1_] = diff;
if (++rg->index1_ == VP8_RANDOM_TABLE_SIZE) rg->index1_ = 0;
if (++rg->index2_ == VP8_RANDOM_TABLE_SIZE) rg->index2_ = 0;
diff = (diff << 1) >> (32 - num_bits); // sign-extend, 0-center
diff = (diff * rg->amp_) >> VP8_RANDOM_DITHER_FIX; // restrict range
diff += 1 << (num_bits - 1); // shift back to 0.5-center
return diff;
}
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"
#endif
#endif /* WEBP_UTILS_RANDOM_H_ */