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TAD: even the slight companding vastly improves low-volume samples but also increases encoded size by a lot

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minjaesong
2025-10-27 01:22:36 +09:00
parent 67f7c091eb
commit 9c27d114fc
3 changed files with 30 additions and 6 deletions
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16
video_encoder/encoder_tad.c
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@@ -215,11 +215,23 @@ static void compress_gamma(float *left, float *right, size_t count) {
}
}
static void compress_mu_law(float *left, float *right, size_t count) {
static float MU = 255.0f;
for (size_t i = 0; i < count; i++) {
// encode(x) = sign(x) * |x|^γ where γ=0.5
float x = left[i];
left[i] = signum(x) * logf(1.0f + MU * fabsf(x)) / logf(1.0f + MU);
float y = right[i];
right[i] = signum(y) * logf(1.0f + MU * fabsf(y)) / logf(1.0f + MU);
}
}
//=============================================================================
// Quantization with Frequency-Dependent Weighting
//=============================================================================
#define LAMBDA_FIXED 5.8f
#define LAMBDA_FIXED 5.0f
// Lambda-based companding encoder (based on Laplacian distribution CDF)
// val must be normalised to [-1,1]
@@ -651,7 +663,7 @@ size_t tad32_encode_chunk(const float *pcm32_stereo, size_t num_samples,
}
// Step 1.1: Compress dynamic range
// compress_gamma(pcm32_left, pcm32_right, num_samples);
compress_gamma(pcm32_left, pcm32_right, num_samples);
// Step 2: M/S decorrelation
ms_decorrelate(pcm32_left, pcm32_right, pcm32_mid, pcm32_side, num_samples);