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TAD: psychoacoustically optimised quantisation

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minjaesong
2025-11-07 03:40:56 +09:00
parent 00c882aa8d
commit d9d395c62c
4 changed files with 64 additions and 48 deletions
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51
video_encoder/encoder_tad.c
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@@ -19,25 +19,32 @@
static const float TAD32_COEFF_SCALARS[] = {64.0f, 45.255f, 32.0f, 22.627f, 16.0f, 11.314f, 8.0f, 5.657f, 4.0f, 2.828f};
// Base quantiser weight table (10 subbands: LL + 9 H bands)
// Linearly spaced from 1.0 (LL) to 2.0 (H9)
// These weights are multiplied by quantiser_scale during quantization
static const float BASE_QUANTISER_WEIGHTS[] = {
1.0f, // LL (L9) - finest preservation
1.0f, // H (L9)
1.0f, // H (L8)
1.0f, // H (L7)
1.0f, // H (L6)
1.1f, // H (L5)
1.2f, // H (L4)
1.3f, // H (L3)
1.4f, // H (L2)
1.5f // H (L1) - coarsest quantization
};
// Forward declarations for internal functions
static void dwt_dd4_forward_1d(float *data, int length);
static void dwt_forward_multilevel(float *data, int length, int levels);
static void quantize_dwt_coefficients(const float *coeffs, int8_t *quantized, size_t count, int apply_deadzone, int chunk_size, int dwt_levels, int quant_bits, int *current_subband_index, float quantiser_scale);
static const float BASE_QUANTISER_WEIGHTS[2][10] = {
{ // mid channel
4.0f, // LL (L9) DC
2.0f, // H (L9) 31.25 hz
1.8f, // H (L8) 62.5 hz
1.6f, // H (L7) 125 hz
1.4f, // H (L6) 250 hz
1.2f, // H (L5) 500 hz
1.0f, // H (L4) 1 khz
1.0f, // H (L3) 2 khz
1.3f, // H (L2) 4 khz
1.8f // H (L1) 8 khz
},
{ // side channel
6.0f, // LL (L9) DC
5.0f, // H (L9) 31.25 hz
2.6f, // H (L8) 62.5 hz
2.4f, // H (L7) 125 hz
1.8f, // H (L6) 250 hz
1.3f, // H (L5) 500 hz
1.0f, // H (L4) 1 khz
1.0f, // H (L3) 2 khz
1.6f, // H (L2) 4 khz
3.2f // H (L1) 8 khz
}};
static inline float FCLAMP(float x, float min, float max) {
return x < min ? min : (x > max ? max : x);
@@ -279,7 +286,7 @@ static int8_t lambda_companding(float val, int max_index) {
return (int8_t)(sign * index);
}
static void quantize_dwt_coefficients(const float *coeffs, int8_t *quantized, size_t count, int apply_deadzone, int chunk_size, int dwt_levels, int max_index, int *current_subband_index, float quantiser_scale) {
static void quantize_dwt_coefficients(int channel, const float *coeffs, int8_t *quantized, size_t count, int apply_deadzone, int chunk_size, int dwt_levels, int max_index, int *current_subband_index, float quantiser_scale) {
int first_band_size = chunk_size >> dwt_levels;
int *sideband_starts = malloc((dwt_levels + 2) * sizeof(int));
@@ -304,7 +311,7 @@ static void quantize_dwt_coefficients(const float *coeffs, int8_t *quantized, si
}
// Apply base weight and quantiser scaling
float weight = BASE_QUANTISER_WEIGHTS[sideband] * quantiser_scale;
float weight = BASE_QUANTISER_WEIGHTS[channel][sideband] * quantiser_scale;
float val = (coeffs[i] / (TAD32_COEFF_SCALARS[sideband] * weight)); // val is normalised to [-1,1]
int8_t quant_val = lambda_companding(val, max_index);
@@ -779,8 +786,8 @@ size_t tad32_encode_chunk(const float *pcm32_stereo, size_t num_samples,
}
// Step 4: Quantize with frequency-dependent weights and quantiser scaling
quantize_dwt_coefficients(dwt_mid, quant_mid, num_samples, 1, num_samples, dwt_levels, max_index, NULL, quantiser_scale);
quantize_dwt_coefficients(dwt_side, quant_side, num_samples, 1, num_samples, dwt_levels, max_index, NULL, quantiser_scale);
quantize_dwt_coefficients(0, dwt_mid, quant_mid, num_samples, 1, num_samples, dwt_levels, max_index, NULL, quantiser_scale);
quantize_dwt_coefficients(1, dwt_side, quant_side, num_samples, 1, num_samples, dwt_levels, max_index, NULL, quantiser_scale);
// Step 4.5: Accumulate quantized coefficient statistics if enabled
if (stats_enabled) {