From 61d9082da668ecac81428027dd6f25f67e91d38b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?kleines=20Filmr=C3=B6llchen?= Date: Sun, 31 Oct 2021 12:31:58 +0100 Subject: [PATCH] LibAudio: Replace log_pan with a constant power panning algoritm This little functional change uses the most common algorithm for panning audio, known as constant power panning. It makes it so that the total output power (not directly the sample value, i.e. the peak) stays the same no matter how the audio is panned. --- Userland/Libraries/LibAudio/Sample.h | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/Userland/Libraries/LibAudio/Sample.h b/Userland/Libraries/LibAudio/Sample.h index 23faf6244a7..50e3c849076 100644 --- a/Userland/Libraries/LibAudio/Sample.h +++ b/Userland/Libraries/LibAudio/Sample.h @@ -90,18 +90,22 @@ struct Sample { return new_frame; } - ALWAYS_INLINE Sample& log_pan(double const pan) + // Constant power panning + ALWAYS_INLINE Sample& pan(double const position) { - left *= linear_to_log(min(pan * -1 + 1.0, 1.0)); - right *= linear_to_log(min(pan + 1.0, 1.0)); + double const pi_over_2 = AK::Pi * 0.5; + double const root_over_2 = AK::sqrt(2.0) * 0.5; + double const angle = position * pi_over_2 * 0.5; + left *= root_over_2 * (AK::cos(angle) - AK::sin(angle)); + right *= root_over_2 * (AK::cos(angle) + AK::sin(angle)); return *this; } - ALWAYS_INLINE Sample log_pan(double const pan) const + ALWAYS_INLINE Sample panned(double const position) const { - Sample new_frame { left, right }; - new_frame.log_pan(pan); - return new_frame; + Sample new_sample { left, right }; + new_sample.pan(position); + return new_sample; } constexpr Sample& operator*=(double const mult)