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TAV: channel-concatenated coeffs preprocessing

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minjaesong
2025-09-29 14:42:52 +09:00
parent 5012ca4085
commit 1d3d218238
5 changed files with 339 additions and 81 deletions
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CLAUDE.md
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@@ -174,7 +174,8 @@ Peripheral memories can be accessed using `vm.peek()` and `vm.poke()` functions,
- **Perceptual quantization**: HVS-optimized coefficient scaling
- **YCoCg-R color space**: Efficient chroma representation with "simulated" subsampling using anisotropic quantization (search for "ANISOTROPY_MULT_CHROMA" on the encoder)
- **6-level DWT decomposition**: Deep frequency analysis for better compression (deeper levels possible but 6 is the maximum for the default TSVM size)
- **Significance Map Compression**: Improved coefficient storage format exploiting sparsity for 15-20% additional compression (2025-09-29 update)
- **Significance Map Compression**: Improved coefficient storage format exploiting sparsity for 16-18% additional compression (2025-09-29 update)
- **Concatenated Maps Layout**: Cross-channel compression optimization for additional 1.6% improvement (2025-09-29 enhanced)
- **Usage Examples**:
```bash
# Different wavelets
@@ -240,10 +241,19 @@ The significance map compression technique implemented on 2025-09-29 provides su
**Technical Approach**:
```
Original: [coeff_array] → [significance_bits + nonzero_values]
Original: [coeff_array] → [concatenated_significance_maps + nonzero_values]
Concatenated Maps Layout:
[Y_map][Co_map][Cg_map][Y_vals][Co_vals][Cg_vals]
- Significance map: 1 bit per coefficient (0=zero, 1=non-zero)
- Value array: Only non-zero coefficients in sequence
- Result: 15-20% compression improvement on typical video content
- Value arrays: Only non-zero coefficients in sequence per channel
- Cross-channel optimization: Zstd finds patterns across similar significance maps
- Result: 16-18% compression improvement + 1.6% additional from concatenation
```
**Performance**: Tested on quantized DWT coefficients with 86.9% sparsity, achieving 16.4% compression improvement before Zstd compression. The technique is particularly effective on high-frequency subbands where sparsity often exceeds 95%.
**Performance**:
- **Sparsity exploitation**: Tested on quantized DWT coefficients with 86.9% sparsity (Y), 97.8% (Co), 99.5% (Cg)
- **Compression improvement**: 16.4% from significance maps + 1.6% from concatenated layout
- **Real-world impact**: 559 bytes saved per frame (5.59 MB per 10k frames)
- **Cross-channel benefit**: Concatenated maps allow Zstd to exploit similarity between significance patterns