# Alterable biquad filters
This is a collection of [digital biquad filters](https://webaudio.github.io/Audio-EQ-Cookbook/audio-eq-cookbook.html) whose parameters `f` (frequency in *Hz*), `g` (gain in *dB*) and `q` (quality) can be varied at runtime. Following [DF1](https://ccrma.stanford.edu/~jos/fp/Direct_Form_I.html) filter implementations are available:
- Allpass
- Bandpass
- Highpass
- Lowpass
- Highshelf
- Lowshelf
- Notch
- Peak
## Basic usage
Filter with static configuration:
```python
import biquad
import numpy as np
# load audio samples somehow
x, sr = np.zeros(...), 44100
# create a filter of your choice
f = biquad.bandpass(sr, f=sr/4, q=1)
# process all audio samples
y = f(x)
```
Filter with dynamic configuration:
```python
import biquad
import numpy as np
# load audio samples somehow
x, sr = np.zeros(...), 44100
# create a filter of your choice
f = biquad.bandpass(sr)
# create parameter modifications as you like
myf = np.linspace(1, sr/4, len(x))
myq = np.linspace(2, 1/2, len(x))
# process all audio samples
y = f(x, f=myf, q=myq)
```
Keep in mind:
- All filters have a default value for the persistent parameters `g` and `q`, which is set in the particular `__init__` method.
- Parameter `f` must be set either in the `__init__` or in the `__call__` method.
- The optional instantaneous parameters `f`, `g` and `q`, if specified in the `__call__` method, override the persistent ones.
## References
1. <span id="1">[Cookbook formulae for audio EQ biquad filter coefficients](https://webaudio.github.io/Audio-EQ-Cookbook/audio-eq-cookbook.html) by Robert Bristow-Johnson</span>
2. <span id="2">[Introduction to Digital Filters with Audio Applications](https://ccrma.stanford.edu/~jos/filters/filters.html) by Julius O. Smith III</span>
## License
[github.com/jurihock/biquad](https://github.com/jurihock/biquad) is licensed under the terms of the MIT license.
For details please refer to the accompanying [LICENSE](https://github.com/jurihock/biquad/raw/main/LICENSE) file distributed with it.
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"description": "# Alterable biquad filters\n\n\n\n\n\nThis is a collection of [digital biquad filters](https://webaudio.github.io/Audio-EQ-Cookbook/audio-eq-cookbook.html) whose parameters `f` (frequency in *Hz*), `g` (gain in *dB*) and `q` (quality) can be varied at runtime. Following [DF1](https://ccrma.stanford.edu/~jos/fp/Direct_Form_I.html) filter implementations are available:\n\n- Allpass\n- Bandpass\n- Highpass\n- Lowpass\n- Highshelf\n- Lowshelf\n- Notch\n- Peak\n\n## Basic usage\n\nFilter with static configuration:\n\n```python\nimport biquad\nimport numpy as np\n\n# load audio samples somehow\nx, sr = np.zeros(...), 44100\n\n# create a filter of your choice\nf = biquad.bandpass(sr, f=sr/4, q=1)\n\n# process all audio samples\ny = f(x)\n```\n\nFilter with dynamic configuration:\n\n```python\nimport biquad\nimport numpy as np\n\n# load audio samples somehow\nx, sr = np.zeros(...), 44100\n\n# create a filter of your choice\nf = biquad.bandpass(sr)\n\n# create parameter modifications as you like\nmyf = np.linspace(1, sr/4, len(x))\nmyq = np.linspace(2, 1/2, len(x))\n\n# process all audio samples\ny = f(x, f=myf, q=myq)\n```\n\nKeep in mind:\n\n- All filters have a default value for the persistent parameters `g` and `q`, which is set in the particular `__init__` method.\n- Parameter `f` must be set either in the `__init__` or in the `__call__` method.\n- The optional instantaneous parameters `f`, `g` and `q`, if specified in the `__call__` method, override the persistent ones. \n\n## References\n\n1. <span id=\"1\">[Cookbook formulae for audio EQ biquad filter coefficients](https://webaudio.github.io/Audio-EQ-Cookbook/audio-eq-cookbook.html) by Robert Bristow-Johnson</span>\n2. <span id=\"2\">[Introduction to Digital Filters with Audio Applications](https://ccrma.stanford.edu/~jos/filters/filters.html) by Julius O. Smith III</span>\n\n## License\n\n[github.com/jurihock/biquad](https://github.com/jurihock/biquad) is licensed under the terms of the MIT license.\nFor details please refer to the accompanying [LICENSE](https://github.com/jurihock/biquad/raw/main/LICENSE) file distributed with it.\n",
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