tape_recorder/core/tape_processor.py

"""
Tape Processor — Simulates tape saturation and applies safety filters.
"""
import numpy as np
from .eq_engine import EQBand, EQEngine
from .calibrator import TAPE_PROFILES

class TapeProcessor:
    def __init__(self, sample_rate: int = 44100):
        self.sample_rate = sample_rate
        
        self.tape_type = "Type I (Ferric)"
        self.enable_highpass = True
        self.enable_lowpass = True
        self.enable_saturation = True
        self.saturation_threshold = 0.95
        
        # Internal filter engine for safety filters
        self._filter_engine = EQEngine(sample_rate)
        self._update_filters()
        
    def _update_filters(self):
        profile = TAPE_PROFILES.get(self.tape_type, TAPE_PROFILES["Type I (Ferric)"])
        
        bands = []
        if self.enable_highpass:
            bands.append(EQBand(freq=profile["low_cut"], gain=0.0, q=0.707, filter_type='highpass'))
        if self.enable_lowpass:
            bands.append(EQBand(freq=profile["high_cut"], gain=0.0, q=0.707, filter_type='lowpass'))
            
        self._filter_engine.bands = bands
        self._filter_engine.update_filters()

    def set_tape_type(self, tape_type: str):
        if tape_type != self.tape_type:
            self.tape_type = tape_type
            self._update_filters()
            
    def set_sample_rate(self, sr: int):
        self.sample_rate = sr
        self._filter_engine.set_sample_rate(sr)

    def process_pre_eq(self, chunk: np.ndarray) -> np.ndarray:
        if chunk.size == 0:
            return chunk
            
        # 1. Apply safety HP/LP filters
        if self.enable_highpass or self.enable_lowpass:
            chunk = self._filter_engine.process(chunk)
            
        return chunk
        
    def process_post_eq(self, chunk: np.ndarray) -> np.ndarray:
        if chunk.size == 0:
            return chunk
            
        # 2. Soft Saturation
        if self.enable_saturation:
            # Scale so threshold maps to where tanh starts rounding off
            scale = 1.0 / max(0.1, self.saturation_threshold)
            chunk = np.tanh(chunk * scale) / scale
            
        return chunk
        
    def reset_state(self):
        self._filter_engine.reset_state()