diff options
| -rw-r--r-- | alc/effects/reverb.cpp | 71 |
1 files changed, 55 insertions, 16 deletions
diff --git a/alc/effects/reverb.cpp b/alc/effects/reverb.cpp index 1af50559..e0d59f36 100644 --- a/alc/effects/reverb.cpp +++ b/alc/effects/reverb.cpp @@ -98,8 +98,6 @@ struct CubicFilter { constexpr CubicFilter gCubicTable; -using namespace std::placeholders; - /* Max samples per process iteration. Used to limit the size needed for * temporary buffers. Must be a multiple of 4 for SIMD alignment. */ @@ -122,12 +120,9 @@ constexpr size_t NUM_LINES{4u}; constexpr float MODULATION_DEPTH_COEFF{0.05f}; -/* The B-Format to A-Format conversion matrix. The arrangement of rows is - * deliberately chosen to align the resulting lines to their spatial opposites - * (0:above front left <-> 3:above back right, 1:below front right <-> 2:below - * back left). It's not quite opposite, since the A-Format results in a - * tetrahedron, but it's close enough. Should the model be extended to 8-lines - * in the future, true opposites can be used. +/* The B-Format to (W-normalized) A-Format conversion matrix. This produces a + * tetrahedral array of discrete signals (boosted by a factor of sqrt(3), to + * reduce the error introduced in the conversion). */ alignas(16) constexpr float B2A[NUM_LINES][NUM_LINES]{ { 0.5f, 0.5f, 0.5f, 0.5f }, @@ -136,7 +131,9 @@ alignas(16) constexpr float B2A[NUM_LINES][NUM_LINES]{ { 0.5f, -0.5f, 0.5f, -0.5f } }; -/* Converts A-Format to B-Format for early reflections. */ +/* Converts (W-normalized) A-Format to B-Format for early reflections (scaled + * by 1/sqrt(3) to compensate for the boost in the B2A matrix). + */ alignas(16) constexpr std::array<std::array<float,NUM_LINES>,NUM_LINES> EarlyA2B{{ {{ 0.5f, 0.5f, 0.5f, 0.5f }}, {{ 0.5f, -0.5f, 0.5f, -0.5f }}, @@ -144,7 +141,11 @@ alignas(16) constexpr std::array<std::array<float,NUM_LINES>,NUM_LINES> EarlyA2B {{ 0.5f, 0.5f, -0.5f, -0.5f }} }}; -/* Converts A-Format to B-Format for late reverb. */ +/* Converts (W-normalized) A-Format to B-Format for late reverb (scaled + * by 1/sqrt(3) to compensate for the boost in the B2A matrix). The response + * is rotated around Z (ambisonic X) so that the front lines are placed + * horizontally in front, and the rear lines are placed vertically in back. + */ constexpr auto InvSqrt2 = static_cast<float>(1.0/al::numbers::sqrt2); alignas(16) constexpr std::array<std::array<float,NUM_LINES>,NUM_LINES> LateA2B{{ {{ 0.5f, 0.5f, 0.5f, 0.5f }}, @@ -330,6 +331,39 @@ struct DelayLineI { } while(--td); } } + + /* Writes the given input lines to the delay buffer, applying a geometric + * reflection. This effectively applies the matrix + * + * [ -1/2 +1/2 +1/2 +1/2 ] + * [ +1/2 -1/2 +1/2 +1/2 ] + * [ +1/2 +1/2 -1/2 +1/2 ] + * [ +1/2 +1/2 +1/2 -1/2 ] + * + * to the four input lines when writing to the delay buffer. The effect on + * the B-Format signal is negating X,Y,Z, moving each response to its + * spatially opposite location. + */ + void writeReflected(size_t offset, const al::span<const ReverbUpdateLine,NUM_LINES> in, + const size_t count) const noexcept + { + ASSUME(count > 0); + for(size_t i{0u};i < count;) + { + offset &= Mask; + size_t td{minz(Mask+1 - offset, count - i)}; + do { + const std::array src{in[0][i], in[1][i], in[2][i], in[3][i]}; + ++i; + + Line[offset][0] = ( src[1] + src[2] + src[3] - src[0]) * 0.5f; + Line[offset][1] = (src[0] + src[2] + src[3] - src[1]) * 0.5f; + Line[offset][2] = (src[0] + src[1] + src[3] - src[2]) * 0.5f; + Line[offset][3] = (src[0] + src[1] + src[2] - src[3]) * 0.5f; + ++offset; + } while(--td); + } + } }; struct VecAllpass { @@ -1337,7 +1371,9 @@ inline auto VectorPartialScatter(const std::array<float,NUM_LINES> &RESTRICT in, }}; } -/* Utilizes the above, but reverses the input channels. */ +/* Utilizes the above, but also applies a geometric reflection on the input + * channels. + */ void VectorScatterRevDelayIn(const DelayLineI delay, size_t offset, const float xCoeff, const float yCoeff, const al::span<const ReverbUpdateLine,NUM_LINES> in, const size_t count) { @@ -1348,9 +1384,13 @@ void VectorScatterRevDelayIn(const DelayLineI delay, size_t offset, const float offset &= delay.Mask; size_t td{minz(delay.Mask+1 - offset, count-i)}; do { - std::array<float,NUM_LINES> f; - for(size_t j{0u};j < NUM_LINES;j++) - f[NUM_LINES-1-j] = in[j][i]; + std::array src{in[0][i], in[1][i], in[2][i], in[3][i]}; + std::array f{ + ( src[1] + src[2] + src[3] - src[0]) * 0.5f, + (src[0] + src[2] + src[3] - src[1]) * 0.5f, + (src[0] + src[1] + src[3] - src[2]) * 0.5f, + (src[0] + src[1] + src[2] - src[3]) * 0.5f + }; ++i; delay.Line[offset++] = VectorPartialScatter(f, xCoeff, yCoeff); @@ -1473,8 +1513,7 @@ void ReverbPipeline::processEarly(size_t offset, const size_t samplesToDo, /* Apply a delay and bounce to generate secondary reflections, combine * with the primary reflections and write out the result for mixing. */ - for(size_t j{0u};j < NUM_LINES;j++) - early_delay.write(offset, NUM_LINES-1-j, tempSamples[j].data(), todo); + early_delay.writeReflected(offset, tempSamples, todo); for(size_t j{0u};j < NUM_LINES;j++) { size_t feedb_tap{offset - mEarly.Offset[j]}; |