88 lines
3.6 KiB
Python
88 lines
3.6 KiB
Python
import numpy as np
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import scipy.signal as signal
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import librosa
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class SubTabDSPEngine:
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@staticmethod
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def change_speed(y: np.ndarray, sr: int, speed_ratio: float, preserve_pitch: bool = True) -> np.ndarray:
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"""
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Alters the playback velocity (Time-Stretching) of a NumPy signal array.
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"""
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if speed_ratio == 1.0:
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return y
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if preserve_pitch:
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return librosa.effects.time_stretch(y, rate=speed_ratio)
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else:
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num_samples_new = int(len(y) / speed_ratio)
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return signal.resample(y, num_samples_new)
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@staticmethod
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def normalize(y: np.ndarray, target_db: float = 0.0) -> np.ndarray:
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"""
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Performs Peak Normalization on an array to scale it to the target decibel value.
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"""
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target_amplitude = 10.0 ** (target_db / 20.0)
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max_amplitude = np.max(np.abs(y))
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if max_amplitude == 0:
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return y
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gain = target_amplitude / max_amplitude
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return y * gain
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@staticmethod
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def merge_back_to_parent(
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parent_track_audio: np.ndarray,
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sr: int,
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edited_sub_audio: np.ndarray,
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start_seconds: float,
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original_duration_seconds: float
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) -> np.ndarray:
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"""
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Splices the modified audio segment from the Sub-tab back into the parent track array.
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Applies a 10ms micro-crossfade at the boundaries to eliminate pop/click noise.
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"""
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start_sample = int(start_seconds * sr)
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original_samples_len = int(original_duration_seconds * sr)
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edited_samples_len = len(edited_sub_audio)
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crossfade_samples = int(0.01 * sr) # 10ms crossfade window
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# 1. Allocate the target output array dimension bounds
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new_total_len = len(parent_track_audio) - original_samples_len + edited_samples_len
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output_audio = np.zeros(new_total_len, dtype=np.float32)
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# 2. Extract leading unedited block
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output_audio[:start_sample] = parent_track_audio[:start_sample]
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# 3. Stitch the modified audio payload
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output_audio[start_sample:start_sample + edited_samples_len] = edited_sub_audio
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# 4. Extract trailing unedited block
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post_start_original = start_sample + original_samples_len
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post_start_new = start_sample + edited_samples_len
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output_audio[post_start_new:] = parent_track_audio[post_start_original:]
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# 5. Execute micro-crossfade across the initial splice junction
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if start_sample > crossfade_samples:
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fade_in_ramp = np.linspace(0.0, 1.0, crossfade_samples)
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fade_out_ramp = np.linspace(1.0, 0.0, crossfade_samples)
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# Smooth 10ms interpolation overlay
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output_audio[start_sample : start_sample + crossfade_samples] = (
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edited_sub_audio[:crossfade_samples] * fade_in_ramp +
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parent_track_audio[start_sample : start_sample + crossfade_samples] * fade_out_ramp
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)
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# 6. Execute micro-crossfade across the trailing splice junction
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if post_start_new + crossfade_samples < len(output_audio):
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fade_in_ramp = np.linspace(0.0, 1.0, crossfade_samples)
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fade_out_ramp = np.linspace(1.0, 0.0, crossfade_samples)
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output_audio[post_start_new : post_start_new + crossfade_samples] = (
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parent_track_audio[post_start_original : post_start_original + crossfade_samples] * fade_in_ramp +
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edited_sub_audio[-crossfade_samples:] * fade_out_ramp
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)
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return output_audio
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