change_video_fps.py

import time

import av
import tqdm
from av.video import VideoStream


desired_fps = 2

timestamp = int(time.time())
input_container = av.open('m3u8_To_MP4.mp4')
output_container = av.open(f"output_{timestamp}.mp4", "w")

in_video_stream: VideoStream = input_container.streams.video[0]

out_video_stream = output_container.add_stream('h264', rate=desired_fps)
out_video_stream.width = in_video_stream.width
out_video_stream.height = in_video_stream.height
out_video_stream.pix_fmt = in_video_stream.pix_fmt
out_video_stream.bit_rate = 16000000

original_fps = int(in_video_stream.average_rate)
save_each_n_frames = round(original_fps/desired_fps)
print(save_each_n_frames)

try:
    for i, frame in tqdm.tqdm(enumerate(input_container.decode(video=0))):
        if i % save_each_n_frames == 0:
            frame.pts = None
            frame.time_base = None
            packet = out_video_stream.encode(frame)
            output_container.mux(packet)

finally:
    input_container.close()
    output_container.close()