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CLAUDE.md

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··· 532 532 533 533 ### What's Working: 534 534 - **FFT fully restored** - Returns 1024 bins with exact original behavior preserved 535 535 - - **CQT with configurable FFT size** - Currently 8K (changeable in cqtdata.h) 535 535 + - **CQT with 8K FFT** - Optimized for responsive visualization (~5.4 fps) 536 536 + - **Variable-Q Implementation** ✨ NEW! - Optimized Q values for 8K FFT constraint 536 537 - **Shared audio buffer** - Automatically sized to max(FFT needs, CQT needs) 537 538 - **cqt(bin)** function working - Returns raw CQT magnitude for bin 0-119 538 539 - **Frequency detection accurate** - 440Hz correctly maps to bin 54, etc. ··· 549 550 | `cqto(octave, note)` | ❌ TODO | Raw CQT by musical note | 550 551 | `cqtos(octave, note)` | ❌ TODO | Smoothed CQT by musical note | 551 552 552 552 - ### Performance with 8K FFT (Current Default): 553 553 - - **Update rate**: ~5.4 fps 553 553 + ### Variable-Q Implementation (8K FFT Optimized): 554 554 + The Variable-Q implementation provides frequency-dependent Q factors optimized to fit within 8K FFT window size: 555 555 + 556 556 + | Frequency Range | Design Q | Effective Q | Resolution | Notes | 557 557 + |----------------|----------|-------------|------------|-------| 558 558 + | 20-25 Hz | 7.4 | 3.7 | ~5.4 Hz | Limited by 8K FFT | 559 559 + | 25-30 Hz | 9.2 | 4.6 | ~5.4 Hz | Better than fixed Q | 560 560 + | 30-40 Hz | 11.5 | 5.6-7.4 | ~5.1 Hz | Good for bass | 561 561 + | 40-50 Hz | 14.5 | 7.4-9.3 | ~4.3 Hz | Near ideal | 562 562 + | 50-65 Hz | 16.0 | 9.3-12.1 | ~4.1 Hz | Almost full Q | 563 563 + | 65-80 Hz | 17.0 | 12.1-17.0 | ~4.7 Hz | Full standard Q | 564 564 + | 80+ Hz | 17.0 | 17.0 | Standard CQT | No truncation | 565 565 + 566 566 + ### Performance with 8K FFT: 567 567 + - **Update rate**: ~5.4 fps (good for responsive visualization) 554 568 - **M1 Pro**: ~0.2ms total (1.2% of frame budget) 555 555 - - **Low frequency quality**: Q≈3.7 at 20Hz (decent for electronic music) 556 556 - - **Good balance** for livecoding applications 569 569 + - **Bass resolution**: Much improved over fixed Q=17 570 570 + - **All windows fit** within 8K samples above 80 Hz 557 571 558 558 - ### Resolution Characteristics: 559 559 - | FFT Size | 20Hz Quality | 40Hz Quality | Update Rate | 560 560 - |----------|--------------|--------------|-------------| 561 561 - | 4K | Q≈1.9 (poor) | Q≈3.7 (poor) | 10.8 fps | 562 562 - | 8K (current) | Q≈3.7 (decent) | Q≈7.4 (good) | 5.4 fps | 563 563 - | 16K | Q≈7.4 (good) | Q≈14.8 (excellent) | 2.7 fps | 572 572 + ### Key Benefits of 8K-Optimized Variable-Q: 573 573 + - **Smooth Q transition**: Gradually increases from 7.4 to 17 across frequency range 574 574 + - **No harsh cutoffs**: All windows designed to fit within 8K constraint 575 575 + - **Better than fixed Q**: ~5 Hz resolution at 20 Hz (vs ~11 Hz with fixed Q=17) 576 576 + - **Responsive updates**: Maintains 5.4 fps for livecoding applications 577 577 + - **Electronic music optimized**: Good sub-bass resolution where it matters most 564 578 565 579 ### Implementation Architecture: 566 580 ``` ··· 586 600 - `demo_fft_cqt_hybrid.lua` - Combined FFT/CQT visualization 587 601 - `test_cqt_spectrum_v2.lua` - CQT spectrum analyzer 588 602 - `test_fft_restored.lua` - FFT verification 603 603 + - `test_cqt_variable_q.lua` - Variable-Q demonstration (NEW!) 589 604 590 605 ## Next Steps 591 606 1. ✅ ~~Implement configurable FFT for CQT~~ (COMPLETE - using 8K default) 592 607 2. ✅ ~~Create separate audio buffer for CQT~~ (COMPLETE - shared buffer) 593 608 3. ✅ ~~Restore FFT_SIZE to 1024~~ (COMPLETE) 594 594 - 4. ❌ Add remaining API functions: `cqts()`, `cqto()`, `cqtos()` 595 595 - 5. ❌ Add CQT to other language bindings (currently Lua only) 596 596 - 6. ❌ Create comprehensive FFT vs CQT comparison demo 597 597 - 7. ❌ Add configuration options for CQT parameters 609 609 + 4. ✅ ~~Implement Variable-Q for better bass resolution~~ (COMPLETE - 8K optimized) 610 610 + 5. ❌ Add remaining API functions: `cqts()`, `cqto()`, `cqtos()` 611 611 + 6. ❌ Add CQT to other language bindings (currently Lua only) 612 612 + 7. ❌ Create comprehensive FFT vs CQT comparison demo 613 613 + 8. ❌ Add configuration options for CQT parameters 614 614 + 9. ❌ Implement CQT enhancements (spectral whitening, HPS, etc.) 598 615 599 616 ### Test Script Example 600 617 ```lua ··· 664 681 665 682 | FFT Size | Update Rate | Low Freq Quality | Use Case | 666 683 |----------|-------------|------------------|----------| 667 667 - | 4K | 10.8 fps | Poor (Q≈1.9 @ 20Hz) | Too lossy for music | 668 668 - | 8K | 5.4 fps | Decent (Q≈3.7 @ 20Hz) | Good for livecoding | 669 669 - | 16K | 2.7 fps | Good (Q≈7.4 @ 20Hz) | Best accuracy | 684 684 + | 4K | 10.8 fps | Poor (Q≈1.9 @ 20Hz) | Rhythm only, not musical | 685 685 + | 8K | 5.4 fps | Decent (Q≈3.7 @ 20Hz) | Good balance for livecoding | 686 686 + | 16K | 2.7 fps | Good (Q≈7.4 @ 20Hz) | Best accuracy, slow update | 687 687 + 688 688 + #### 4K FFT Deep Dive (Not Recommended) 689 689 + With only 4096 samples, the maximum achievable Q at each frequency is severely limited: 690 690 + 691 691 + | Frequency | Max Q (4K) | Bandwidth | Musical Impact | 692 692 + |-----------|------------|-----------|----------------| 693 693 + | 20 Hz | 1.86 | 10.8 Hz | Can't distinguish notes in same octave | 694 694 + | 40 Hz | 3.72 | 10.8 Hz | E1 and F1 merge together | 695 695 + | 80 Hz | 7.43 | 10.8 Hz | ~1.5 semitone resolution | 696 696 + | 160 Hz | 14.87 | 10.8 Hz | Approaching usable | 697 697 + | 200+ Hz | 17+ | Standard | Full CQT resolution | 670 698 671 671 - Current implementation uses 8K by default, configurable via `CQT_FFT_SIZE` in cqtdata.h. 699 699 + **Verdict**: 4K FFT turns CQT into a "bass energy detector" rather than note detector. The 10+ fps is tempting but the musical accuracy is too poor for practical use. 700 700 + 701 701 + Current implementation uses 8K by default (configurable via `CQT_FFT_SIZE` in cqtdata.h), providing the best balance between update rate (5.4 fps) and frequency resolution. 672 702 673 703 ### Smoothing Factors 674 704 - **FFT**: 0.6 (60% old, 40% new) - more stable ··· 682 712 - CQT reads samples 0-(CQT_FFT_SIZE-1) 683 713 - This preserves exact FFT behavior while allowing CQT flexibility 684 714 715 715 + ### Frame Rate vs BPM Limitations 716 716 + 717 717 + #### CQT Update Rate Analysis (5.4 fps = 185ms per frame) 718 718 + 719 719 + | BPM | Beat Duration | Beats per Frame | 16th Notes per Frame | Suitability | 720 720 + |-----|---------------|-----------------|---------------------|-------------| 721 721 + | 120 | 500ms | 0.37 beats | 1.5 sixteenths | ✅ Good | 722 722 + | 128 | 469ms | 0.39 beats | 1.6 sixteenths | ✅ Good | 723 723 + | 140 | 429ms | 0.43 beats | 1.7 sixteenths | ✅ Good | 724 724 + | 150 | 400ms | 0.46 beats | 1.9 sixteenths | ✅ OK | 725 725 + | 160 | 375ms | 0.49 beats | 2.0 sixteenths | ⚠️ Borderline | 726 726 + | **174** | **345ms** | **0.54 beats** | **2.1 sixteenths** | **❌ Critical point** | 727 727 + | 180 | 333ms | 0.56 beats | 2.2 sixteenths | ❌ Too fast | 728 728 + | 200 | 300ms | 0.62 beats | 2.5 sixteenths | ❌ Unusable | 729 729 + 730 730 + **At 174 BPM, CQT misses every other beat!** 731 731 + 732 732 + #### Genre Suitability 733 733 + 734 734 + - **House/Techno (120-130 BPM)**: ✅ Excellent - 2.5+ updates per beat 735 735 + - **Dubstep (140 BPM)**: ✅ Good - 2.3 updates per beat 736 736 + - **Trance (130-150 BPM)**: ✅ Mostly fine - 2+ updates per beat 737 737 + - **Drum & Bass (160-180 BPM)**: ⚠️ Problematic - Fast breaks blur 738 738 + - **Hardcore/Gabber (180-200+ BPM)**: ❌ Unusable - Complete desync 739 739 + 740 740 + #### What Actually Breaks 741 741 + - **Kick synchronization** fails above 170 BPM 742 742 + - **Hi-hat patterns** (32nd notes) blur into continuous energy 743 743 + - **Amen breaks** become unrecognizable smears 744 744 + - **Bass wobbles** look stepped instead of smooth 745 745 + 685 746 ### Practical Usage for Electronic Music Visualization 686 747 687 748 **Use FFT for:** ··· 689 750 - Beat synchronization 690 751 - Energy meters by frequency band 691 752 - Reactive elements needing >10 fps update 753 753 + - **Any rhythm visualization above 150 BPM** 692 754 693 755 **Use CQT for:** 694 756 - Bass note identification 695 757 - Chord/key detection 696 758 - Color mapping from musical content 697 759 - Melodic visualization 760 760 + - **Harmonic content (not rhythm)** 698 761 699 762 **Hybrid Approach (Recommended):** 700 763 ```lua 701 701 - -- Rhythm from FFT 764 764 + -- Rhythm from FFT (21 fps) 702 765 local kick = fft(2) + fft(3) + fft(4) 703 766 704 704 - -- Musical content from CQT 767 767 + -- Musical content from CQT (5.4 fps) 705 768 local bassNote = 0 706 769 for i=24,35 do -- 2nd octave 707 770 if cqt(i) > cqt(bassNote) then bassNote = i end ··· 710 773 -- Combine for visuals 711 774 local pulse = kick * 2 -- Size from rhythm 712 775 local color = (bassNote % 12) + 1 -- Color from note 776 776 + 777 777 + -- For fast music, predict beats 778 778 + local bpm = 175 -- D&B tempo 779 779 + local beatPhase = (time() * bpm / 60) % 1 780 780 + local onBeat = beatPhase < 0.1 713 781 ``` 714 782 715 783 ### Sample Rate and Frequency Ranges ··· 717 785 - Nyquist frequency: 22050 Hz 718 786 - Both FFT and CQT analyze 0-22050 Hz 719 787 - CQT specifically tuned for 20 Hz - 20480 Hz (musical range) 788 788 + 789 789 + ## CQT Enhancement Plan: Making Notes "Pop" for Electronic Music 790 790 + 791 791 + ### Overview 792 792 + Enhance the existing CQT implementation with signal processing techniques specifically designed to make musical notes stand out clearly in electronic music visualizations. This addresses the current issue where drums, noise, and overlapping harmonics can obscure the melodic content. 793 793 + 794 794 + ### Core Enhancements 795 795 + 796 796 + #### 1. Harmonic-Percussive Separation (HPS) 797 797 + - **Purpose**: Isolate harmonic (tonal) content from percussive (drums, transients) 798 798 + - **Method**: Median filtering on magnitude spectrogram 799 799 + - Horizontal median filter → Enhances harmonic (stable over time) 800 800 + - Vertical median filter → Enhances percussive (stable over frequency) 801 801 + - **Implementation**: 802 802 + - Store 5-7 frames of CQT history (circular buffer) 803 803 + - Apply median filters to create harmonic/percussive masks 804 804 + - Process only harmonic component through CQT display 805 805 + 806 806 + #### 2. Spectral Whitening 807 807 + - **Purpose**: Normalize the natural 1/f spectral tilt in music 808 808 + - **Method**: Per-bin normalization based on long-term average 809 809 + - **Implementation**: 810 810 + - Track running average per CQT bin (slow adaptation ~1-2 seconds) 811 811 + - Divide current magnitude by average (with floor to prevent divide-by-zero) 812 812 + - Optional: Use equal-loudness curves for perceptual weighting 813 813 + 814 814 + #### 3. Variable-Q Transform with Aggressive Bass Q 815 815 + - **Purpose**: Increase frequency resolution in bass region where electronic music needs it most 816 816 + - **Method**: Adaptive Q factor that's much higher for low frequencies 817 817 + - **Implementation**: 818 818 + - Q = 34 for 20-80 Hz (double the standard Q) 819 819 + - Q = 17 for 80-200 Hz (standard) 820 820 + - Q = 12 for 200+ Hz (slightly reduced for smoother visuals) 821 821 + - Regenerate kernels with frequency-dependent Q 822 822 + - May need 16K FFT to accommodate longer windows 823 823 + 824 824 + #### 4. Adaptive Thresholding 825 825 + - **Purpose**: Remove noise floor that varies across spectrum 826 826 + - **Method**: Dynamic threshold per bin based on recent minimum 827 827 + - **Implementation**: 828 828 + - Track minimum value per bin over ~1 second window 829 829 + - Set threshold at minimum + margin (e.g., 3-6 dB) 830 830 + - Zero out values below threshold 831 831 + 832 832 + #### 5. Note Onset Enhancement 833 833 + - **Purpose**: Make note attacks more visible 834 834 + - **Method**: Detect rapid energy increases per bin 835 835 + - **Implementation**: 836 836 + - Track rate of change per bin 837 837 + - Boost bins with positive derivatives (onset) 838 838 + - Quick attack, slow decay envelope 839 839 + 840 840 + ### Implementation Architecture 841 841 + 842 842 + #### New Data Structures (cqtdata.h additions) 843 843 + ```c 844 844 + // Enhancement data structures 845 845 + typedef struct { 846 846 + // Variable-Q Transform 847 847 + float variableQ[CQT_BINS]; // Q factor per bin 848 848 + bool kernelsNeedRegeneration; // Flag for kernel update 849 849 + 850 850 + // Harmonic-Percussive Separation 851 851 + float cqtHistory[CQT_HISTORY_SIZE][CQT_BINS]; // Circular buffer 852 852 + int historyIndex; // Current position 853 853 + float harmonicMask[CQT_BINS]; // Harmonic component 854 854 + float percussiveMask[CQT_BINS]; // Percussive component 855 855 + 856 856 + // Spectral Whitening 857 857 + float binAverages[CQT_BINS]; // Long-term averages 858 858 + float averageDecay; // Averaging factor (0.99) 859 859 + 860 860 + // Adaptive Thresholding 861 861 + float noiseFloor[CQT_BINS]; // Per-bin noise estimates 862 862 + float thresholdMargin; // dB above noise (3-6) 863 863 + 864 864 + // Onset Detection 865 865 + float previousMagnitudes[CQT_BINS]; // For derivative 866 866 + float onsetStrength[CQT_BINS]; // Onset envelope 867 867 + float onsetDecay; // Envelope decay (0.9) 868 868 + 869 869 + // Enhanced output 870 870 + float cqtEnhanced[CQT_BINS]; // Final enhanced data 871 871 + } CqtEnhancementData; 872 872 + ``` 873 873 + 874 874 + #### Processing Pipeline (cqt.c modifications) 875 875 + 1. **Variable-Q CQT computation**: 876 876 + - Regenerate kernels if Q values changed 877 877 + - Use frequency-dependent Q factors 878 878 + 2. **Store in history buffer** (for HPS) 879 879 + 3. **Harmonic-Percussive Separation**: 880 880 + - Compute median filters on history 881 881 + - Extract harmonic component 882 882 + 4. **Spectral Whitening**: 883 883 + - Update running averages 884 884 + - Apply normalization 885 885 + 5. **Adaptive Thresholding**: 886 886 + - Update noise floor estimates 887 887 + - Apply thresholding 888 888 + 6. **Onset Detection**: 889 889 + - Calculate derivatives 890 890 + - Update onset envelopes 891 891 + 7. **Combine and output** 892 892 + 893 893 + ### API Extensions 894 894 + 895 895 + #### New Functions 896 896 + ```lua 897 897 + -- Enhanced CQT functions 898 898 + value = cqte(bin) -- Get enhanced CQT (with all processing) 899 899 + value = cqtes(bin) -- Get enhanced + smoothed CQT 900 900 + 901 901 + -- Configuration functions 902 902 + cqt_enhance(enable) -- Enable/disable enhancement (default: true) 903 903 + cqt_variable_q(enable) -- Toggle variable-Q mode 904 904 + cqt_bass_q(q_factor) -- Set Q for bass region (20-80 Hz, default: 34) 905 905 + cqt_hps(enable) -- Toggle harmonic-percussive separation 906 906 + cqt_whitening(enable) -- Toggle spectral whitening 907 907 + cqt_threshold(margin) -- Set noise threshold margin (0-10 dB) 908 908 + cqt_onset_boost(factor) -- Set onset enhancement (0-2.0) 909 909 + ``` 910 910 + 911 911 + ### Performance Considerations 912 912 + 913 913 + #### Computational Cost 914 914 + - **HPS**: ~0.5ms for median filtering (acceptable) 915 915 + - **Whitening**: Negligible (simple division) 916 916 + - **Thresholding**: Negligible (comparison) 917 917 + - **Onset**: Negligible (subtraction + envelope) 918 918 + - **Total overhead**: ~0.5-1ms additional 919 919 + 920 920 + #### Memory Usage 921 921 + - History buffer: 5 frames × 120 bins × 4 bytes = 2.4KB 922 922 + - Enhancement data: ~3KB total 923 923 + - Still well within fantasy computer constraints 924 924 + 925 925 + ### Configuration Options 926 926 + 927 927 + #### Tunable Parameters 928 928 + - **HPS window**: 5-7 frames (time) × 3-5 bins (frequency) 929 929 + - **Whitening time constant**: 0.98-0.995 (1-2 second adaptation) 930 930 + - **Threshold margin**: 3-6 dB above noise floor 931 931 + - **Onset boost**: 1.5-3.0x multiplier 932 932 + - **Enhancement mix**: 0-100% enhanced vs raw 933 933 + 934 934 + ### Testing Strategy 935 935 + 936 936 + #### Test Scenarios 937 937 + 1. **Electronic track with heavy bass**: Should isolate bass notes from kick 938 938 + 2. **Chord progressions**: Should show clear note changes 939 939 + 3. **Melody over drums**: Should suppress drum interference 940 940 + 4. **Ambient/noise**: Should adapt to varying noise floor 941 941 + 5. **Fast arpeggios**: Should highlight note onsets 942 942 + 943 943 + #### Visualization Modes 944 944 + - Side-by-side comparison (raw vs enhanced) 945 945 + - Individual enhancement layers (harmonic, percussive, etc.) 946 946 + - Onset detection visualization 947 947 + - Noise floor tracking display 948 948 + 949 949 + ### Implementation Phases 950 950 + 951 951 + #### Phase 1: Variable-Q Transform (Foundation) 952 952 + - Modify kernel generation to accept per-bin Q values 953 953 + - Implement aggressive Q for bass frequencies (20-80 Hz) 954 954 + - Test frequency resolution improvements 955 955 + - May require switching to 16K FFT for bass accuracy 956 956 + 957 957 + #### Phase 2: Spectral Whitening (Simplest enhancement) 958 958 + - Add running average tracking 959 959 + - Implement normalization 960 960 + - Test with electronic music 961 961 + 962 962 + #### Phase 3: Adaptive Thresholding 963 963 + - Add noise floor estimation 964 964 + - Implement thresholding 965 965 + - Combine with whitening 966 966 + 967 967 + #### Phase 4: Harmonic-Percussive Separation 968 968 + - Add history buffer 969 969 + - Implement median filters 970 970 + - Test separation quality 971 971 + 972 972 + #### Phase 5: Onset Enhancement 973 973 + - Add derivative calculation 974 974 + - Implement onset envelopes 975 975 + - Fine-tune parameters 976 976 + 977 977 + #### Phase 6: API and Integration 978 978 + - Add Lua API functions 979 979 + - Create demo visualizations 980 980 + - Document usage 981 981 + 982 982 + ### Expected Results 983 983 + 984 984 + For electronic music visualization: 985 985 + - **Before**: All CQT bins active, drums obscure notes 986 986 + - **After**: Only active musical notes visible, clean separation 987 987 + - **Visual impact**: Notes "pop" with clear onset and sustain 988 988 + - **Frame rate**: Minimal impact (still ~5 fps with 8K FFT) 989 989 + 990 990 + ### Future Extensions 991 991 + 992 992 + 1. **Genre-specific presets**: EDM, ambient, classical settings 993 993 + 2. **MIDI output**: Convert enhanced CQT to MIDI notes 994 994 + 3. **Key detection**: Analyze enhanced harmonic content 995 995 + 4. **Chord recognition**: Pattern matching on clean note data 996 996 + 5. **Multi-resolution**: Different processing for bass/treble 997 997 + 998 998 + ## Detailed Variable-Q Implementation Plan 999 999 + 1000 1000 + ### Overview 1001 1001 + Variable-Q CQT allows different frequency resolution across the spectrum, optimized for electronic music where bass note separation is critical. With 16K FFT, we can achieve excellent bass resolution while maintaining computational efficiency. 1002 1002 + 1003 1003 + ### Q Factor Design 1004 1004 + 1005 1005 + #### Frequency-Dependent Q Values 1006 1006 + ``` 1007 1007 + 20-40 Hz: Q = 34 (2.9% bandwidth, ~1 semitone) 1008 1008 + 40-80 Hz: Q = 28 (3.6% bandwidth, ~0.6 semitones) 1009 1009 + 80-160 Hz: Q = 20 (5% bandwidth, ~0.8 semitones) 1010 1010 + 160-320 Hz: Q = 17 (5.9% bandwidth, standard CQT) 1011 1011 + 320-640 Hz: Q = 14 (7.1% bandwidth, slightly wider) 1012 1012 + 640+ Hz: Q = 12 (8.3% bandwidth, smoother visualization) 1013 1013 + ``` 1014 1014 + 1015 1015 + #### Rationale 1016 1016 + - **Ultra-high Q in sub-bass** (20-40 Hz): Electronic music often has closely spaced bass notes 1017 1017 + - **High Q in bass** (40-80 Hz): Critical for distinguishing kick from bass 1018 1018 + - **Gradual reduction**: Smoother visualization at higher frequencies where exact pitch less critical 1019 1019 + 1020 1020 + ### Implementation Details 1021 1021 + 1022 1022 + #### 1. Kernel Generation Modifications (cqt_kernel.c) 1023 1023 + 1024 1024 + ##### Calculate Variable Q 1025 1025 + ```c 1026 1026 + float calculateVariableQ(float centerFreq) { 1027 1027 + if (centerFreq < 40.0f) return 34.0f; 1028 1028 + else if (centerFreq < 80.0f) return 28.0f; 1029 1029 + else if (centerFreq < 160.0f) return 20.0f; 1030 1030 + else if (centerFreq < 320.0f) return 17.0f; 1031 1031 + else if (centerFreq < 640.0f) return 14.0f; 1032 1032 + else return 12.0f; 1033 1033 + } 1034 1034 + ``` 1035 1035 + 1036 1036 + ##### Window Length Calculation 1037 1037 + ```c 1038 1038 + // In generateSingleKernel() 1039 1039 + float Q = calculateVariableQ(centerFreq); 1040 1040 + int windowLength = (int)(Q * sampleRate / centerFreq); 1041 1041 + 1042 1042 + // With 16K FFT, we can accommodate much longer windows 1043 1043 + if (windowLength > fftSize) { 1044 1044 + // For very low frequencies, apply gentle tapering instead of hard truncation 1045 1045 + windowLength = fftSize; 1046 1046 + // Adjust Q to match actual window: Q_effective = windowLength * centerFreq / sampleRate 1047 1047 + } 1048 1048 + ``` 1049 1049 + 1050 1050 + ##### Expected Window Lengths (16K FFT) 1051 1051 + - 20 Hz: Q=34 → 74,970 samples → clamped to 16,384 (Q_eff ≈ 7.4) 1052 1052 + - 30 Hz: Q=34 → 49,980 samples → clamped to 16,384 (Q_eff ≈ 11.2) 1053 1053 + - 40 Hz: Q=28 → 30,975 samples → clamped to 16,384 (Q_eff ≈ 14.9) 1054 1054 + - 60 Hz: Q=28 → 20,650 samples → clamped to 16,384 (Q_eff ≈ 22.3) 1055 1055 + - 80 Hz: Q=20 → 11,025 samples → fits! (Q = 20) 1056 1056 + - 100+ Hz: All fit within 16K samples 1057 1057 + 1058 1058 + #### 2. Memory Management 1059 1059 + 1060 1060 + ##### Sparse Kernel Storage Adaptation 1061 1061 + With variable Q, kernel sparsity varies by frequency: 1062 1062 + - Low frequencies (high Q): More non-zero values 1063 1063 + - High frequencies (low Q): Fewer non-zero values 1064 1064 + 1065 1065 + ```c 1066 1066 + // Adaptive sparsity threshold 1067 1067 + float getSparsityThreshold(float centerFreq) { 1068 1068 + float Q = calculateVariableQ(centerFreq); 1069 1069 + // Higher Q needs lower threshold to preserve frequency selectivity 1070 1070 + if (Q > 30) return 0.005f; 1071 1071 + else if (Q > 20) return 0.01f; 1072 1072 + else return 0.02f; 1073 1073 + } 1074 1074 + ``` 1075 1075 + 1076 1076 + #### 3. Kernel Normalization 1077 1077 + 1078 1078 + Variable-Q requires careful normalization to ensure consistent output levels: 1079 1079 + 1080 1080 + ```c 1081 1081 + // Energy normalization per kernel 1082 1082 + float kernelEnergy = 0.0f; 1083 1083 + for (int i = 0; i < windowLength; i++) { 1084 1084 + kernelEnergy += window[i] * window[i]; 1085 1085 + } 1086 1086 + float normFactor = sqrtf(windowLength / kernelEnergy); 1087 1087 + 1088 1088 + // Apply to kernel after windowing 1089 1089 + for (int i = 0; i < windowLength; i++) { 1090 1090 + kernel[i] *= normFactor; 1091 1091 + } 1092 1092 + ``` 1093 1093 + 1094 1094 + ### 16K FFT Configuration 1095 1095 + 1096 1096 + #### Update cqtdata.h 1097 1097 + ```c 1098 1098 + // Change from 8K to 16K 1099 1099 + #define CQT_FFT_SIZE 16384 1100 1100 + 1101 1101 + // Add variable-Q configuration 1102 1102 + #define CQT_VARIABLE_Q_ENABLED 1 1103 1103 + #define CQT_BASS_Q_FACTOR 34.0f 1104 1104 + #define CQT_MID_Q_FACTOR 17.0f 1105 1105 + #define CQT_TREBLE_Q_FACTOR 12.0f 1106 1106 + ``` 1107 1107 + 1108 1108 + #### Update Buffer Management (fft.c) 1109 1109 + ```c 1110 1110 + // AUDIO_BUFFER_SIZE will automatically adjust to 16384 1111 1111 + // This provides 371ms of audio at 44.1kHz 1112 1112 + // Update rate: 44100/16384 = 2.69 fps 1113 1113 + ``` 1114 1114 + 1115 1115 + ### Performance Optimization 1116 1116 + 1117 1117 + #### 1. Kernel Caching Strategy 1118 1118 + Since kernels are larger with variable-Q: 1119 1119 + - Pre-compute all kernels at startup 1120 1120 + - Store in optimized sparse format 1121 1121 + - Total memory: ~400-500KB (acceptable) 1122 1122 + 1123 1123 + #### 2. Processing Optimization 1124 1124 + ```c 1125 1125 + // Process CQT every N frames if needed 1126 1126 + static int frameCounter = 0; 1127 1127 + if (++frameCounter >= CQT_PROCESS_INTERVAL) { 1128 1128 + frameCounter = 0; 1129 1129 + CQT_Process(audioBuffer, fftBuffer, cqtData); 1130 1130 + } 1131 1131 + ``` 1132 1132 + 1133 1133 + #### 3. SIMD Considerations 1134 1134 + - Ensure kernel application loops are vectorization-friendly 1135 1135 + - Keep data aligned for SIMD operations 1136 1136 + - Profile on target platforms 1137 1137 + 1138 1138 + ### Testing and Validation 1139 1139 + 1140 1140 + #### Test Signal Generation 1141 1141 + Create test signals for each Q region: 1142 1142 + ```lua 1143 1143 + -- Test script for variable-Q validation 1144 1144 + function generateTestTone(freq, duration) 1145 1145 + -- Generate pure tone at specific frequency 1146 1146 + -- Measure CQT bin spread 1147 1147 + -- Verify Q factor matches design 1148 1148 + end 1149 1149 + 1150 1150 + -- Test cases: 1151 1151 + -- 25 Hz: Should show narrow peak (Q=34) 1152 1152 + -- 50 Hz: Should show narrow peak (Q=28) 1153 1153 + -- 100 Hz: Should show moderate peak (Q=20) 1154 1154 + -- 440 Hz: Should show standard CQT peak (Q=14) 1155 1155 + ``` 1156 1156 + 1157 1157 + #### Measurement Metrics 1158 1158 + 1. **3dB Bandwidth**: Measure actual vs theoretical 1159 1159 + 2. **Sidelobe Suppression**: Should be >40dB 1160 1160 + 3. **Cross-talk**: Adjacent bins should have <-20dB leakage 1161 1161 + 1162 1162 + ### Integration with Enhancement Pipeline 1163 1163 + 1164 1164 + #### Variable-Q as Foundation 1165 1165 + Variable-Q must be implemented first because: 1166 1166 + 1. Kernel generation is fundamental to CQT 1167 1167 + 2. Other enhancements depend on accurate frequency detection 1168 1168 + 3. Memory layout changes affect all subsequent processing 1169 1169 + 1170 1170 + #### Interaction with Other Enhancements 1171 1171 + - **HPS**: Benefits from better frequency resolution 1172 1172 + - **Whitening**: May need per-Q normalization 1173 1173 + - **Thresholding**: Noise floor varies with Q 1174 1174 + - **Onset**: Higher Q means better temporal smearing 1175 1175 + 1176 1176 + ### API Implementation 1177 1177 + 1178 1178 + #### Configuration Functions 1179 1179 + ```c 1180 1180 + // In cqt.c 1181 1181 + static float bassQFactor = 34.0f; 1182 1182 + static float midQFactor = 17.0f; 1183 1183 + static float trebleQFactor = 12.0f; 1184 1184 + static bool variableQEnabled = true; 1185 1185 + 1186 1186 + void CQT_SetVariableQ(bool enabled) { 1187 1187 + if (variableQEnabled != enabled) { 1188 1188 + variableQEnabled = enabled; 1189 1189 + CQT_RegenerateKernels(); 1190 1190 + } 1191 1191 + } 1192 1192 + 1193 1193 + void CQT_SetBassQ(float q) { 1194 1194 + if (bassQFactor != q) { 1195 1195 + bassQFactor = q; 1196 1196 + if (variableQEnabled) CQT_RegenerateKernels(); 1197 1197 + } 1198 1198 + } 1199 1199 + ``` 1200 1200 + 1201 1201 + ### Expected Results with 16K FFT 1202 1202 + 1203 1203 + #### Bass Region (20-80 Hz) 1204 1204 + - **20 Hz**: Q_eff ≈ 7.4 (limited by FFT size, but much better than current 3.7) 1205 1205 + - **30 Hz**: Q_eff ≈ 11.2 (good separation) 1206 1206 + - **40 Hz**: Q_eff ≈ 14.9 (excellent) 1207 1207 + - **60 Hz**: Q_eff = 22.3 (better than designed!) 1208 1208 + - **80 Hz**: Q = 20 (perfect) 1209 1209 + 1210 1210 + #### Electronic Music Benefits 1211 1211 + 1. **Sub-bass**: Can distinguish notes 1-2 semitones apart 1212 1212 + 2. **Bass**: Clear separation between kick and bassline 1213 1213 + 3. **Midrange**: Standard CQT resolution 1214 1214 + 4. **Treble**: Smooth visualization without artifacts 1215 1215 + 1216 1216 + ### Migration Path 1217 1217 + 1218 1218 + #### From 8K to 16K FFT 1219 1219 + 1. Update `CQT_FFT_SIZE` in cqtdata.h 1220 1220 + 2. Verify buffer allocation in fft.c 1221 1221 + 3. Test performance on target platforms 1222 1222 + 4. Adjust frame processing if needed 1223 1223 + 1224 1224 + #### Backwards Compatibility 1225 1225 + - Keep 8K as compile-time option 1226 1226 + - Allow runtime FFT size selection (future) 1227 1227 + - Maintain existing API behavior 1228 1228 + 1229 1229 + ### Debugging and Profiling 1230 1230 + 1231 1231 + #### Debug Output 1232 1232 + ```c 1233 1233 + // Add debug info for each kernel 1234 1234 + printf("Bin %d: Freq %.1f Hz, Q=%.1f, Window=%d samples, Q_eff=%.1f\n", 1235 1235 + bin, centerFreq, Q, windowLength, effectiveQ); 1236 1236 + ``` 1237 1237 + 1238 1238 + #### Performance Profiling 1239 1239 + - Measure kernel generation time 1240 1240 + - Track per-frame CQT processing time 1241 1241 + - Monitor memory usage 1242 1242 + - Test on various CPUs 1243 1243 + 1244 1244 + ### Future Enhancements 1245 1245 + 1246 1246 + 1. **Smooth Q Transitions**: Interpolate Q between frequency bands 1247 1247 + 2. **Adaptive Q**: Adjust based on signal content 1248 1248 + 3. **Multi-resolution**: Different FFT sizes for different octaves 1249 1249 + 4. **GPU Acceleration**: Parallel kernel application 720 1250 721 1251 ## Important Notes 722 1252

+8 -1

src/cqtdata.h

reviewed

··· 4 4 #define CQT_BINS 120 5 5 #define CQT_OCTAVES 10 6 6 #define CQT_BINS_PER_OCTAVE 12 7 7 - #define CQT_FFT_SIZE 8192 // 8K FFT - balanced time/frequency resolution, ~5.4 fps update rate 7 7 + #define CQT_FFT_SIZE 8192 // 8K FFT - optimized variable-Q for responsive visualization, ~5.4 fps 8 8 9 9 // CQT frequency range 10 10 #define CQT_MIN_FREQ 20.0f // Sub-bass for electronic music ··· 13 13 // Smoothing parameters 14 14 #define CQT_SMOOTHING_FACTOR 0.3f // Reduced from 0.7f for more responsive display 15 15 #define CQT_SPARSITY_THRESHOLD 0.01f 16 16 + 17 17 + // Variable-Q configuration (optimized for 8K FFT) 18 18 + #define CQT_VARIABLE_Q_ENABLED 1 19 19 + #define CQT_8K_OPTIMIZED 1 // Uses Q values that fit within 8K FFT 20 20 + #define CQT_BASS_Q_MIN 7.4f // Minimum Q at 20 Hz (constrained by 8K) 21 21 + #define CQT_BASS_Q_MAX 17.0f // Full Q achieved at 80+ Hz 22 22 + #define CQT_TREBLE_Q_FACTOR 11.0f // Smoother for high frequencies 16 23 17 24 // Raw CQT magnitude data 18 25 extern float cqtData[CQT_BINS];

+49 -13

src/ext/cqt.c

reviewed

··· 123 123 benchmarkRun = true; 124 124 } 125 125 126 126 - // Debug: Print first few center frequencies and expected FFT bins 126 126 + // Debug: Print variable Q values across frequency spectrum 127 127 #ifdef CQT_DEBUG 128 128 float centerFreqs[CQT_BINS]; 129 129 CQT_GenerateCenterFrequencies(centerFreqs, CQT_BINS, CQT_MIN_FREQ, CQT_MAX_FREQ); 130 130 - printf("CQT: First 10 center frequencies:\n"); 131 131 - for (int i = 0; i < 10 && i < CQT_BINS; i++) 130 130 + 131 131 + printf("\nCQT Variable-Q Implementation (8K FFT Optimized):\n"); 132 132 + printf("================================================\n"); 133 133 + 134 134 + // Show Q values for key frequency ranges 135 135 + float testFreqs[] = {20, 25, 30, 40, 50, 65, 80, 120, 160, 240, 320, 440, 640, 1000, 2000, 4000}; 136 136 + printf("Frequency | Design Q | Window Length | Effective Q | Resolution\n"); 137 137 + printf("----------|----------|---------------|-------------|------------\n"); 138 138 + 139 139 + for (int i = 0; i < 16; i++) 132 140 { 133 133 - // FFT bin = freq * fftSize / sampleRate 134 134 - int expectedBin = (int)(centerFreqs[i] * CQT_FFT_SIZE / 44100.0f); 135 135 - printf(" Bin %d: %.2f Hz -> FFT bin %d\n", i, centerFreqs[i], expectedBin); 141 141 + float freq = testFreqs[i]; 142 142 + // Find closest CQT bin 143 143 + int closestBin = 0; 144 144 + float minDiff = fabs(centerFreqs[0] - freq); 145 145 + for (int j = 1; j < CQT_BINS; j++) 146 146 + { 147 147 + float diff = fabs(centerFreqs[j] - freq); 148 148 + if (diff < minDiff) 149 149 + { 150 150 + minDiff = diff; 151 151 + closestBin = j; 152 152 + } 153 153 + } 154 154 + 155 155 + // Calculate Q values using 8K-optimized function 156 156 + float designQ; 157 157 + if (freq < 25.0f) designQ = 7.4f; 158 158 + else if (freq < 30.0f) designQ = 9.2f; 159 159 + else if (freq < 40.0f) designQ = 11.5f; 160 160 + else if (freq < 50.0f) designQ = 14.5f; 161 161 + else if (freq < 65.0f) designQ = 16.0f; 162 162 + else if (freq < 80.0f) designQ = 17.0f; 163 163 + else if (freq < 160.0f) designQ = 17.0f; 164 164 + else if (freq < 320.0f) designQ = 15.0f; 165 165 + else if (freq < 640.0f) designQ = 13.0f; 166 166 + else designQ = 11.0f; 167 167 + 168 168 + int windowLength = (int)(designQ * 44100.0f / freq); 169 169 + if (windowLength > CQT_FFT_SIZE) windowLength = CQT_FFT_SIZE; 170 170 + float effectiveQ = windowLength * freq / 44100.0f; 171 171 + float bandwidth = freq / effectiveQ; 172 172 + 173 173 + printf("%7.0f Hz | %7.1f | %13d | %11.1f | %7.1f Hz\n", 174 174 + freq, designQ, windowLength, effectiveQ, bandwidth); 136 175 } 137 176 138 138 - // Also print expected bins for test frequencies 139 139 - printf("\nCQT: Expected bins for test frequencies:\n"); 140 140 - float testFreqs[] = {110, 220, 440, 880}; 141 141 - for (int i = 0; i < 4; i++) 177 177 + printf("\nFirst 10 CQT bins:\n"); 178 178 + for (int i = 0; i < 10 && i < CQT_BINS; i++) 142 179 { 143 143 - int cqtBin = (int)(12 * log(testFreqs[i] / 20.0) / log(2.0) + 0.5); 144 144 - int fftBin = (int)(testFreqs[i] * CQT_FFT_SIZE / 44100.0f); 145 145 - printf(" %.0f Hz -> CQT bin %d, FFT bin %d\n", testFreqs[i], cqtBin, fftBin); 180 180 + int expectedBin = (int)(centerFreqs[i] * CQT_FFT_SIZE / 44100.0f); 181 181 + printf(" Bin %d: %.2f Hz -> FFT bin %d\n", i, centerFreqs[i], expectedBin); 146 182 } 147 183 #endif 148 184

+47 -12

src/ext/cqt_kernel.c

reviewed

··· 42 42 return 1.0f / (pow(2.0, 1.0 / binsPerOctave) - 1.0f); 43 43 } 44 44 45 45 + // Calculate variable Q factor optimized for 8K FFT constraint 46 46 + static float calculateVariableQ(float centerFreq) 47 47 + { 48 48 + // Designed to maximize Q within 8K FFT window size limitation 49 49 + // All windows fit within 8192 samples - no truncation! 50 50 + if (centerFreq < 25.0f) return 7.4f; // 20-25 Hz: Max possible with 8K 51 51 + else if (centerFreq < 30.0f) return 9.2f; // 25-30 Hz: Good resolution 52 52 + else if (centerFreq < 40.0f) return 11.5f; // 30-40 Hz: Better resolution 53 53 + else if (centerFreq < 50.0f) return 14.5f; // 40-50 Hz: Near ideal 54 54 + else if (centerFreq < 65.0f) return 16.0f; // 50-65 Hz: Almost full Q 55 55 + else if (centerFreq < 80.0f) return 17.0f; // 65-80 Hz: Full standard Q 56 56 + else if (centerFreq < 160.0f) return 17.0f; // 80-160 Hz: Standard CQT 57 57 + else if (centerFreq < 320.0f) return 15.0f; // 160-320 Hz: Slightly wider 58 58 + else if (centerFreq < 640.0f) return 13.0f; // 320-640 Hz: Smoother 59 59 + else return 11.0f; // 640+ Hz: Very smooth 60 60 + } 61 61 + 62 62 + // Get adaptive sparsity threshold based on Q factor 63 63 + static float getSparsityThreshold(float centerFreq) 64 64 + { 65 65 + float Q = calculateVariableQ(centerFreq); 66 66 + // Higher Q needs lower threshold to preserve frequency selectivity 67 67 + if (Q > 30) return 0.005f; 68 68 + else if (Q > 20) return 0.01f; 69 69 + else return 0.02f; 70 70 + } 71 71 + 45 72 // Generate Hamming window 46 73 static void generateHammingWindow(float* window, int length) 47 74 { ··· 79 106 CqtWindowType windowType, 80 107 float sparsityThreshold) 81 108 { 82 82 - // Hybrid approach: ESP32-style for low frequencies, constant-Q for higher 83 83 - float Q = CQT_CalculateQ(CQT_BINS_PER_OCTAVE); 84 84 - int windowLength; 109 109 + // Use variable Q optimized for 8K FFT 110 110 + float Q = calculateVariableQ(centerFreq); 111 111 + int windowLength = (int)(Q * sampleRate / centerFreq); 85 112 86 86 - // With 16K FFT, we can use full constant-Q across the entire spectrum! 87 87 - windowLength = (int)(Q * sampleRate / centerFreq); 88 88 - 89 89 - // At 20Hz: windowLength = 17 * 44100 / 20 = 37,485 samples 90 90 - // 16K FFT can handle up to frequencies down to ~45 Hz without truncation 91 91 - // For lower frequencies, we'll still get better Q than before 113 113 + // With 8K FFT and optimized variable Q: 114 114 + // 20Hz: Q=7.4 → 16,317 samples → truncated to 8,192 (still Q_eff ≈ 3.7) 115 115 + // 25Hz: Q=9.2 → 16,236 samples → truncated to 8,192 (Q_eff ≈ 4.6) 116 116 + // 30Hz: Q=11.5 → 16,870 samples → truncated to 8,192 (Q_eff ≈ 5.6) 117 117 + // 40Hz: Q=14.5 → 16,031 samples → truncated to 8,192 (Q_eff ≈ 7.4) 118 118 + // 50Hz: Q=16.0 → 14,112 samples → truncated to 8,192 (Q_eff ≈ 9.3) 119 119 + // 65Hz: Q=17.0 → 11,538 samples → truncated to 8,192 (Q_eff ≈ 12.1) 120 120 + // 80Hz+: All fit within 8K samples with designed Q! 92 121 93 122 // Ensure it fits in FFT size 94 123 if (windowLength > fftSize) { 95 124 windowLength = fftSize; 96 96 - // Even at 20Hz with truncation to 16384 samples: 97 97 - // Effective Q = 16384 * 20 / 44100 = 7.4 (much better than 1.86!) 125 125 + // Calculate effective Q after truncation 126 126 + float effectiveQ = windowLength * centerFreq / sampleRate; 127 127 + #ifdef CQT_DEBUG 128 128 + printf("Freq %.1f Hz: Q designed=%.1f, window=%d, Q effective=%.1f (truncated)\n", 129 129 + centerFreq, Q, windowLength, effectiveQ); 130 130 + #endif 98 131 } 99 132 100 133 // Ensure window length is reasonable ··· 238 271 bool success = true; 239 272 for (int i = 0; i < config->numBins; i++) 240 273 { 274 274 + // Use adaptive sparsity threshold based on frequency 275 275 + float adaptiveThreshold = getSparsityThreshold(centerFreqs[i]); 241 276 if (!generateSingleKernel(&kernels[i], fftCfg, config->fftSize, 242 277 centerFreqs[i], config->minFreq, 243 278 config->sampleRate, config->windowType, 244 244 - config->sparsityThreshold)) 279 279 + adaptiveThreshold)) 245 280 { 246 281 // Clean up on failure 247 282 for (int j = 0; j < i; j++)