static kBitCostThreshold affects compression ratio #54

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claunia · 2026-01-29T20:30:18Z

claunia commented

2026-01-29 20:30:18 +00:00

Originally created by @tesseract2048 on GitHub (Oct 11, 2015).

encode.cc:392

      static const int kSampleRate = 13;
      static const double kMinEntropy = 7.92;
      static const double kBitCostThreshold = bytes * kMinEntropy / kSampleRate;

kBitCostThreshold is cached once initialized.
However, if brotli library is reused within the same process, first compress a small piece of data, then a large one will suffer from poor compression ratio, since some block will be misleadingly uncompressed.

Originally created by @tesseract2048 on GitHub (Oct 11, 2015). `encode.cc`:392 ``` static const int kSampleRate = 13; static const double kMinEntropy = 7.92; static const double kBitCostThreshold = bytes * kMinEntropy / kSampleRate; ``` kBitCostThreshold is cached once initialized. However, if brotli library is reused within the same process, first compress a small piece of data, then a large one will suffer from poor compression ratio, since some block will be misleadingly uncompressed.

claunia referenced this issue

2026-01-29 20:46:34 +00:00

[PR #54] [MERGED] Use FastLog2() instead of log() in BitsEntropy(). #644

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Reference: starred/brotli#54