如何使用gstreamer保存mp4视频中的所有帧

import gi
gi.require_version('Gst', '1.0')
from gi.repository import Gst

def save_frames_from_mp4(input_file, output_directory):
    Gst.init(None)

    pipeline = Gst.parse_launch("filesrc location={} ! qtdemux ! h264parse ! avdec_h264 ! videoconvert ! pngenc ! multifilesink location={}/frame%05d.png".format(input_file, output_directory))

    bus = pipeline.get_bus()
    pipeline.set_state(Gst.State.PLAYING)

    while True:
        message = bus.timed_pop_filtered(Gst.CLOCK_TIME_NONE, Gst.MessageType.ERROR | Gst.MessageType.EOS)
        if message:
            if message.type == Gst.MessageType.ERROR:
                error, debug_info = message.parse_error()
                print("Error received from element {}: {}".format(message.src.get_name(), error.message))
                print("Debugging information: {}".format(debug_info if debug_info else "none"))
                break
            elif message.type == Gst.MessageType.EOS:
                print("End-Of-Stream reached")
                break

    pipeline.set_state(Gst.State.NULL)

save_frames_from_mp4("input.mp4", "output_directory")

python save_frames.py input.mp4 output_directory