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73bb3c8530
- Improved compression for triangular meshes (~10%) - Added WebAssembly decoder - Code cleanup + robustness fixes
54 lines
2.1 KiB
C++
54 lines
2.1 KiB
C++
// Copyright 2016 The Draco Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// File providing shared funcionality for RAnsSymbolEncoder and
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// RAnsSymbolDecoder (see rans_symbol_encoder.h / rans_symbol_decoder.h).
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#ifndef DRACO_CORE_RANS_SYMBOL_CODING_H_
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#define DRACO_CORE_RANS_SYMBOL_CODING_H_
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#include "core/ans.h"
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namespace draco {
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// Computes the desired precision of the rANS method for the specified maximal
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// symbol bit length of the input data.
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constexpr int ComputeRAnsUnclampedPrecision(int max_bit_length) {
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return (3 * max_bit_length) / 2;
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}
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// Computes the desired precision clamped to guarantee a valid funcionality of
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// our rANS library (which is between 12 to 20 bits).
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constexpr int ComputeRAnsPrecisionFromMaxSymbolBitLength(int max_bit_length) {
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return ComputeRAnsUnclampedPrecision(max_bit_length) < 12
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? 12
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: ComputeRAnsUnclampedPrecision(max_bit_length) > 20
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? 20
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: ComputeRAnsUnclampedPrecision(max_bit_length);
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}
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// Compute approximate frequency table size needed for storing the provided
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// symbols.
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static int64_t ApproximateRAnsFrequencyTableBits(int32_t max_value,
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int num_unique_symbols) {
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// Approximate number of bits for storing zero frequency entries using the
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// run length encoding (with max length of 64).
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const int64_t table_zero_frequency_bits =
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8 * (num_unique_symbols + (max_value - num_unique_symbols) / 64);
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return 8 * num_unique_symbols + table_zero_frequency_bits;
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}
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} // namespace draco
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#endif // DRACO_CORE_RANS_SYMBOL_CODING_H_
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