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TAV: less aggressive deadzonning

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minjaesong
2025-10-07 15:27:55 +09:00
parent 581b270c31
commit 3c9441e67f
2 changed files with 112 additions and 45 deletions
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6
CLAUDE.md
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@@ -196,10 +196,10 @@ Peripheral memories can be accessed using `vm.peek()` and `vm.poke()` functions,
**CRITICAL IMPLEMENTATION NOTES**:
**Wavelet Coefficient Layout**:
- TAV uses **linear subband layout** in memory: `[LL, LH, HL, HH, LH, HL, HH, ...]` for each decomposition level
- TAV uses **2D Spatial Layout** in memory: `[LL, LH, HL, HH, LH, HL, HH, ...]` for each decomposition level
- **Forward transform must output**: `temp[0...half-1] = low-pass`, `temp[half...length-1] = high-pass`
- **Inverse transform must expect**: Same linear layout and exactly reverse forward operations
- **Common mistake**: Assuming interleaved or 2D spatial layout leads to grid/checkerboard artifacts
- **Inverse transform must expect**: Same 2D spatial layout and exactly reverse forward operations
- **Common mistake**: Assuming linear layout leads to grid/checkerboard artifacts
**Wavelet Implementation Pattern**:
- All wavelets must follow the **exact same structure** as the working 5/3 implementation:

151
video_encoder/encoder_tav.c
View File

@@ -188,7 +188,7 @@ static const int QUALITY_ALPHA[] = {79, 47, 23, 11, 5, 2, 1}; // 96, 48, 24, 12,
// Dead-zone quantisation thresholds per quality level
// Higher values = more aggressive (more coefficients set to zero)
static const float DEAD_ZONE_THRESHOLD[] = {1.5f, 1.5f, 1.2f, 1.0f, 0.8f, 0.6f, 0.0f};
static const float DEAD_ZONE_THRESHOLD[] = {1.5f, 1.5f, 1.2f, 1.1f, 0.8f, 0.6f, 0.0f};
// Dead-zone scaling factors for different subband levels
#define DEAD_ZONE_FINEST_SCALE 1.0f // Full dead-zone for finest level (level 6)
@@ -582,7 +582,10 @@ static void show_usage(const char *program_name);
static tav_encoder_t* create_encoder(void);
static void cleanup_encoder(tav_encoder_t *enc);
static int initialise_encoder(tav_encoder_t *enc);
static int get_subband_level_2d(int x, int y, int width, int height, int decomp_levels);
static int get_subband_type_2d(int x, int y, int width, int height, int decomp_levels);
static int get_subband_level(int linear_idx, int width, int height, int decomp_levels);
static int get_subband_type(int linear_idx, int width, int height, int decomp_levels);
static void rgb_to_ycocg(const uint8_t *rgb, float *y, float *co, float *cg, int width, int height);
static int calculate_max_decomp_levels(int width, int height);
@@ -1348,20 +1351,33 @@ static void quantise_dwt_coefficients(float *coeffs, int16_t *quantised, int siz
for (int i = 0; i < size; i++) {
float quantised_val = coeffs[i] / effective_q;
// Apply dead-zone quantisation ONLY to luma channel and finest subbands
// Apply dead-zone quantisation ONLY to luma channel and specific subbands
// Chroma channels skip dead-zone (already heavily quantised, avoid colour banding)
// Pattern: HH1 (full), LH1/HL1/HH2 (half), LH2/HL2 (none), others (none)
// Note: Level 1 is finest (280x224), Level 6 is coarsest (8x7)
if (dead_zone_threshold > 0.0f && !is_chroma) {
int level = get_subband_level(i, width, height, decomp_levels);
int subband_type = get_subband_type(i, width, height, decomp_levels);
float level_threshold = 0.0f;
if (level == decomp_levels) {
// Finest level (level 6): full dead-zone
level_threshold = dead_zone_threshold * DEAD_ZONE_FINEST_SCALE;
} else if (level == decomp_levels - 1) {
// Second-finest level (level 5): reduced dead-zone
level_threshold = dead_zone_threshold * DEAD_ZONE_FINE_SCALE;
if (level == 1) {
// Finest level (level 1: 280x224)
if (subband_type == 3) {
// HH1: full dead-zone
level_threshold = dead_zone_threshold * DEAD_ZONE_FINEST_SCALE;
} else if (subband_type == 1 || subband_type == 2) {
// LH1, HL1: half dead-zone
level_threshold = dead_zone_threshold * DEAD_ZONE_FINE_SCALE;
}
} else if (level == 2) {
// Second-finest level (level 2: 140x112)
if (subband_type == 3) {
// HH2: half dead-zone
level_threshold = dead_zone_threshold * DEAD_ZONE_FINE_SCALE;
}
// LH2, HL2: no dead-zone
}
// Coarser levels (0-4): no dead-zone to preserve structural information
// Coarser levels (3-6): no dead-zone to preserve structural information
if (fabsf(quantised_val) <= level_threshold) {
quantised_val = 0.0f;
@@ -1463,39 +1479,77 @@ static float get_perceptual_weight(tav_encoder_t *enc, int level0, int subband_t
}
// Determine perceptual weight for coefficient at linear position (matches actual DWT layout)
// Get decomposition level for a coefficient at linear index
// Returns: 0 for LL subband, 1-decomp_levels for detail subbands
static int get_subband_level(int linear_idx, int width, int height, int decomp_levels) {
int offset = 0;
// Get decomposition level and subband type for coefficient at 2D spatial position
// Coefficients are stored in 2D spatial (quad-tree) layout, not linear subband layout
// Returns: level (1=finest to decomp_levels=coarsest, 0 for LL)
static int get_subband_level_2d(int x, int y, int width, int height, int decomp_levels) {
// Recursively determine which level this coefficient belongs to
// by checking which quadrant it's in at each level
// First: LL subband at maximum decomposition level
int ll_width = width >> decomp_levels;
int ll_height = height >> decomp_levels;
int ll_size = ll_width * ll_height;
for (int level = 1; level <= decomp_levels; level++) {
int half_w = width >> 1;
int half_h = height >> 1;
if (linear_idx < offset + ll_size) {
return 0; // LL subband (coarsest)
}
offset += ll_size;
// Then: LH, HL, HH subbands for each level from max down to 1
for (int level = decomp_levels; level >= 1; level--) {
int level_width = width >> (decomp_levels - level + 1);
int level_height = height >> (decomp_levels - level + 1);
int subband_size = level_width * level_height;
// Check all three subbands (LH, HL, HH) at this level
if (linear_idx < offset + (subband_size * 3)) {
return level; // Return decomposition level (1-6)
// Check if in top-left quadrant (LL - contains finer levels)
if (x < half_w && y < half_h) {
// Continue to finer level
width = half_w;
height = half_h;
continue;
}
offset += subband_size * 3;
// In one of the detail bands (LH, HL, HH) at this level
return level;
}
// Fallback for out-of-bounds indices
// Reached LL subband at coarsest level
return 0;
}
// Get subband type for coefficient at 2D spatial position
// Returns: 0=LL, 1=LH, 2=HL, 3=HH
static int get_subband_type_2d(int x, int y, int width, int height, int decomp_levels) {
// Recursively determine which subband this coefficient belongs to
for (int level = 1; level <= decomp_levels; level++) {
int half_w = width >> 1;
int half_h = height >> 1;
// Check if in top-left quadrant (LL - contains finer levels)
if (x < half_w && y < half_h) {
// Continue to finer level
width = half_w;
height = half_h;
continue;
}
// Determine which detail band at this level
if (x >= half_w && y < half_h) {
return 1; // LH (top-right)
} else if (x < half_w && y >= half_h) {
return 2; // HL (bottom-left)
} else {
return 3; // HH (bottom-right)
}
}
// Reached LL subband at coarsest level
return 0;
}
// Legacy functions kept for compatibility - convert linear index to 2D coords
static int get_subband_level(int linear_idx, int width, int height, int decomp_levels) {
int x = linear_idx % width;
int y = linear_idx / width;
return get_subband_level_2d(x, y, width, height, decomp_levels);
}
static int get_subband_type(int linear_idx, int width, int height, int decomp_levels) {
int x = linear_idx % width;
int y = linear_idx / width;
return get_subband_type_2d(x, y, width, height, decomp_levels);
}
static float get_perceptual_weight_for_position(tav_encoder_t *enc, int linear_idx, int width, int height, int decomp_levels, int is_chroma) {
// Map linear coefficient index to DWT subband using same layout as decoder
int offset = 0;
@@ -1555,20 +1609,33 @@ static void quantise_dwt_coefficients_perceptual_per_coeff(tav_encoder_t *enc,
float effective_q = effective_base_q * weight;
float quantised_val = coeffs[i] / effective_q;
// Apply dead-zone quantisation ONLY to luma channel and finest subbands
// Apply dead-zone quantisation ONLY to luma channel and specific subbands
// Chroma channels skip dead-zone (already heavily quantised, avoid colour banding)
// Pattern: HH1 (full), LH1/HL1/HH2 (half), LH2/HL2 (none), others (none)
// Note: Level 1 is finest (280x224), Level 6 is coarsest (8x7)
if (enc->dead_zone_threshold > 0.0f && !is_chroma) {
int level = get_subband_level(i, width, height, decomp_levels);
int subband_type = get_subband_type(i, width, height, decomp_levels);
float level_threshold = 0.0f;
if (level == decomp_levels) {
// Finest level (level 6): full dead-zone
level_threshold = enc->dead_zone_threshold * DEAD_ZONE_FINEST_SCALE;
} else if (level == decomp_levels - 1) {
// Second-finest level (level 5): reduced dead-zone
level_threshold = enc->dead_zone_threshold * DEAD_ZONE_FINE_SCALE;
if (level == 1) {
// Finest level (level 1: 280x224)
if (subband_type == 3) {
// HH1: full dead-zone
level_threshold = enc->dead_zone_threshold * DEAD_ZONE_FINEST_SCALE;
} else if (subband_type == 1 || subband_type == 2) {
// LH1, HL1: half dead-zone
level_threshold = enc->dead_zone_threshold * DEAD_ZONE_FINE_SCALE;
}
} else if (level == 2) {
// Second-finest level (level 2: 140x112)
if (subband_type == 3) {
// HH2: half dead-zone
level_threshold = enc->dead_zone_threshold * DEAD_ZONE_FINE_SCALE;
}
// LH2, HL2: no dead-zone
}
// Coarser levels (0-4): no dead-zone to preserve structural information
// Coarser levels (3-6): no dead-zone to preserve structural information
if (fabsf(quantised_val) <= level_threshold) {
quantised_val = 0.0f;