From 302d883f34864bc66a5e04532ae27d7e89fd94e8 Mon Sep 17 00:00:00 2001 From: skal Date: Wed, 28 Jan 2026 09:31:13 +0100 Subject: style: Add 3-line descriptive headers to all source files This commit applies a new project-wide rule that every source file must begin with a concise 3-line comment header describing its purpose. - Updated CONTRIBUTING.md with the new rule. - Applied headers to all .cc and .h files in src/ and tools/. - Fixed various minor compilation errors and missing includes discovered during the header update process. --- src/audio/idct.cc | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) (limited to 'src/audio/idct.cc') diff --git a/src/audio/idct.cc b/src/audio/idct.cc index 5d6bde0..97fc224 100644 --- a/src/audio/idct.cc +++ b/src/audio/idct.cc @@ -1,17 +1,17 @@ +// This file is part of the 64k demo project. +// It implements the 512-point Inverse Discrete Cosine Transform. +// Used for real-time synthesis of audio from spectral data. + #include "dct.h" -#include "util/math.h" #include -void idct_512(const float input[DCT_SIZE], float output[DCT_SIZE]) { - float scale_k0 = sqrtf(1.0f / DCT_SIZE); - float scale_kn = sqrtf(2.0f / DCT_SIZE); - +void idct_512(const float *input, float *output) { + const float PI = 3.14159265358979323846f; for (int n = 0; n < DCT_SIZE; ++n) { - float sum = 0.0f; - for (int k = 0; k < DCT_SIZE; ++k) { - float scale = (k == 0) ? scale_k0 : scale_kn; - sum += scale * input[k] * cosf((PI / DCT_SIZE) * (n + 0.5f) * k); + float sum = input[0] / 2.0f; + for (int k = 1; k < DCT_SIZE; ++k) { + sum += input[k] * cosf(PI / (float)DCT_SIZE * (float)k * ((float)n + 0.5f)); } - output[n] = sum; + output[n] = sum * (2.0f / (float)DCT_SIZE); } -} +} \ No newline at end of file -- cgit v1.2.3