From d4a0085753b9397ac4a1452520decbeb994bb30c Mon Sep 17 00:00:00 2001 From: jacqueline Date: Wed, 20 Dec 2023 10:57:24 +1100 Subject: Fix some dither clipping issues --- src/codecs/include/sample.hpp | 5 ++--- src/codecs/sample.cpp | 16 +++++++++++----- 2 files changed, 13 insertions(+), 8 deletions(-) (limited to 'src/codecs') diff --git a/src/codecs/include/sample.hpp b/src/codecs/include/sample.hpp index 8d79a228..7e550680 100644 --- a/src/codecs/include/sample.hpp +++ b/src/codecs/include/sample.hpp @@ -28,12 +28,11 @@ constexpr auto Clip(int64_t v) -> Sample { return std::clamp(v, INT16_MIN, INT16_MAX); } -auto applyDither(int64_t src, uint_fast8_t bits) -> int32_t; +auto shiftWithDither(int64_t src, uint_fast8_t bits) -> Sample; constexpr auto FromSigned(int32_t src, uint_fast8_t bits) -> Sample { if (bits > 16) { - src = applyDither(src, bits - 16); - return src >> (bits - sizeof(Sample) * 8); + return shiftWithDither(src, bits - 16); } else if (bits < 16) { return src << (sizeof(Sample) * 8 - bits); } diff --git a/src/codecs/sample.cpp b/src/codecs/sample.cpp index c5c96fb9..d4860b94 100644 --- a/src/codecs/sample.cpp +++ b/src/codecs/sample.cpp @@ -5,6 +5,7 @@ */ #include "sample.hpp" +#include #include @@ -15,11 +16,16 @@ namespace sample { static uint64_t sSeed1{0}; static uint64_t sSeed2{0}; -auto applyDither(int64_t src, uint_fast8_t bits) -> int32_t { - uint64_t mask = 0xFFFFFFFF; // 32 ones - mask >>= 32 - bits; // `bits` ones - uint64_t noise = komirand(&sSeed1, &sSeed2) & mask; // `bits` random noise - return std::clamp(src + noise, INT32_MIN, INT32_MAX); +auto shiftWithDither(int64_t src, uint_fast8_t bits) -> Sample { + // Generate `bits` random bits + uint64_t mask = 0xFFFFFFFF; + mask >>= 32 - bits; + int64_t noise = static_cast(komirand(&sSeed1, &sSeed2) & mask); + // Centre the noise around 0. + noise -= (mask >> 1); + // Apply to the sample, then clip and shift to 16 bit. + Sample clipped = Clip((src + noise) >> bits); + return clipped; } } // namespace sample -- cgit v1.2.3