155 lines
4.5 KiB
Markdown
155 lines
4.5 KiB
Markdown
# Spectrogram Viewer (C/Raylib)
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A real-time spectrogram viewer ported from the Unity Audio-Experiments project, with interactive region selection and audio playback.
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## Features
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- **Spectrogram Visualization**: Displays frequency content of audio over time using STFT
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- **Time & Frequency Selection**: Select both time regions AND frequency ranges
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- **Audio Playback**: Play back only the selected time region
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- **Multiple Colormaps**: 6 different heat map styles
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- **Adjustable Threshold**: Control the dB floor for visualization
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- **Drag & Drop**: Load files by dragging them onto the window
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## Building
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### Linux
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```bash
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cd rspektrum/build
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./premake5 gmake
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cd ..
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make
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```
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## Running
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```bash
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cd rspektrum/bin/Debug
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./rspektrum
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```
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## Controls
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| Key | Action |
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|-----|--------|
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| **O** | Open file dialog |
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| **Drag & drop** | Load WAV file |
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| **LMB Drag** | Select time region |
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| **Shift+LMB Drag** | Select frequency range |
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| **SPACE** | Play selected time region |
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| **M** | Cycle colormap |
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| **W/S** | Adjust dB floor (up/down) |
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| **G** | Toggle grid overlay |
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| **R** | Reset all selections to full range |
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| **ESC** | Stop playback / Cancel dialog |
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## File Loading
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Two ways to load a WAV file:
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1. **Drag & Drop**: Simply drag a `.wav` file onto the application window
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2. **File Dialog**: Press **O** to open a file path input dialog
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## Selection Modes
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### Time Selection (Left Mouse Button)
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- Click and drag horizontally to select a time range
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- The non-selected areas are greyed out
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- Yellow borders indicate the selection boundaries
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### Frequency Selection (Shift + Left Mouse Button)
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- Hold **Shift** and drag vertically to select a frequency range
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- Cyan borders indicate the frequency selection
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- Useful for isolating specific frequency bands
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## Colormaps
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Press **M** to cycle through available colormaps:
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1. **Grays** - Classic grayscale
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2. **Inferno** - Dark purple to bright yellow (default)
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3. **Viridis** - Purple to yellow (perceptually uniform)
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4. **Plasma** - Purple to yellow-orange
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5. **Hot** - Black to red to yellow to white
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6. **Cool** - Cyan to magenta
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## Threshold Control
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Use **W** and **S** keys to adjust the amplitude floor:
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- **W**: Raise the floor (show only louder signals)
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- **S**: Lower the floor (show quieter signals too)
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The current dB floor is displayed in the bottom right corner.
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## Technical Details
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### STFT Parameters
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- **FFT Size**: 2048 samples
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- **Hop Size**: 1024 samples (50% overlap)
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- **Window**: Hann window
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- **Frequency Resolution**: `sampleRate / 2048` Hz per bin
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### Audio Format Support
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- WAV files (any sample rate)
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- Automatically detected sample rate (displayed in info panel)
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- 8-bit, 16-bit PCM, and 32-bit float supported
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- Stereo files are converted to mono
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### Display
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- X-axis: Time (seconds)
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- Y-axis: Frequency (Hz), scaled to actual sample rate
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- Color/brightness: Amplitude in dB
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## Project Structure
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```
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rspektrum/
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├── src/
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│ ├── spectrogram.c # Main application (~1000 lines)
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│ └── icon.ico # Windows icon
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├── libs/
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│ └── ... # Optional external libraries
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├── build/
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│ ├── premake5.lua # Build configuration
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│ └── external/ # Downloaded dependencies (raylib)
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└── bin/
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├── Debug/ # Debug build
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└── Release/ # Release build
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```
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## Comparison: Unity vs C/Raylib
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| Aspect | Unity Original | C/Raylib Port |
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|--------|---------------|---------------|
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| Lines of Code | ~2000+ (multiple files) | ~1000 (single file) |
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| Build Time | Minutes | Seconds |
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| Dependencies | Unity Editor, .NET | raylib only |
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| GPU Acceleration | Compute shaders | CPU-based |
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| Colormaps | Single gradient | 6 presets |
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| Freq Selection | No | Yes |
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| Startup Time | Slow | Fast |
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## Tips
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1. **For 16kHz audio**: The max frequency will show as 8kHz (Nyquist)
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2. **Better visibility**: Use Inferno or Viridis colormap for better contrast
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3. **Quiet signals**: Lower the dB floor with 'S' to see quieter content
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4. **Isolate frequencies**: Use Shift+drag to focus on specific frequency bands
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5. **Playback**: Only the time selection is played, full frequency range
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## Future Improvements
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- [ ] Logarithmic frequency scale option
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- [ ] Zoom in/out on frequency axis
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- [ ] Real-time microphone input
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- [ ] Export selection as WAV
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- [ ] Faster FFT (pffft/kissfft)
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- [ ] Save/load presets
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## License
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Based on Unity Audio-Experiments by Sebastian Lague (Coding Adventure series)
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C/Raylib port created for educational purposes.
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