Code for aligning two videos with different framerates

align.py

import numpy as np

duration = 60*60
num_frames = 30* duration
error_percent = .02

a = np.linspace(0, duration, num_frames)
b = np.linspace(0, duration, num_frames * (1 - error_percent))


def closest_sorted(l, x):
    """Returns the index of the closest value in an ascending sorted list l to x."""
    # Get the index of the value on the right side of the zero crossing
    i = np.searchsorted(l, x)
    if i > 0 and abs(l[i] - x) > abs(l[i-1] - x):
        # The item on the left of the zero crossing exists and was smaller
        return i-1
    else: 
        return i

def create_alignment_mapping(a, b):
    """Given two lists of timestamps, return a new list with the index
    of the closest item in b for each value in a."""
    return [closest_sorted(b, t) for t in a]


test = create_alignment_mapping(a, b)
print(test[1000]) # should return 980