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Rework complex16_mag_squared_to_dbv_norm() to use log2.

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Small code size reduction and improvement in CPU effort.
This commit is contained in:
Jared Boone 2016-02-08 12:35:20 -08:00
parent 3aabd804d3
commit cdd15fcf79
1 changed files with 8 additions and 4 deletions
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12
firmware/common/utility.cpp
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@ -61,10 +61,14 @@ uint32_t gcd(const uint32_t u, const uint32_t v) {
#endif #endif
float complex16_mag_squared_to_dbv_norm(const float c16_mag_squared) { float complex16_mag_squared_to_dbv_norm(const float c16_mag_squared) {
constexpr float mag2_max = -32768.0f * -32768.0f + -32768.0f * -32768.0f; constexpr float input_component_max = 32768;
constexpr float mag2_log10_max = std::log10(mag2_max); constexpr float mag2_max = (input_component_max * input_component_max) * 2;
constexpr float mag2_to_db_factor = 20.0f / 2.0f; constexpr float mag2_log2_max = std::log2(mag2_max);
return (std::log10(c16_mag_squared) - mag2_log10_max) * mag2_to_db_factor; constexpr float log_mag2_mag_factor = 0.5f;
constexpr float log2_log10_factor = std::log10(2.0f);
constexpr float log10_dbv_factor = 20.0f;
constexpr float mag2_to_db_factor = log_mag2_mag_factor * log2_log10_factor * log10_dbv_factor;
return (std::log2(c16_mag_squared) - mag2_log2_max) * mag2_to_db_factor;
} }
/* GCD implementation derived from recursive implementation at /* GCD implementation derived from recursive implementation at