[Python] Decoding the h.264 stream from a COM port

I would like to know if there is a reliable way to decode an H.264 NAL stream coming through a serial port using software.

So far, I have managed to decode a single frame using a python script. In this script, I first write the incoming data to a file, and when the end-of-frame marker 00_00_00_01 appears, I display the frame using ffplay.

import serial
import subprocess
import os
import time

ser = serial.Serial('COM3', 115200, timeout=1)
output_file = "output.264"

# Variable to store the ffplay process
ffplay_process = None

# Open the file for writing in binary mode
with open(output_file, "wb") as file:

print("Writing bytes to output.264. Waiting for the end-of-frame marker 0x00000001.")

buffer = bytearray()
marker = b'\x00\x00\x00\x01'

try:
while True:
if ser.in_waiting: # If there is data in the buffer
data = ser.read(ser.in_waiting) # Read all available bytes
buffer.extend(data)

# Check if the end-of-frame marker is in the buffer
while marker in buffer:
index = buffer.index(marker) + len(marker) # Position after the marker
frame = buffer[:index] # Extract the frame
buffer = buffer[index:] # Keep the remaining data

print(f"Frame recorded: {len(frame)} bytes")
file.write(frame) # Write the frame to the file
file.flush() # Force writing to disk

# Close the ffplay window if it is already open
if ffplay_process and ffplay_process.poll() is None:
ffplay_process.terminate()
ffplay_process.wait() # Wait for the process to terminate

# Play the recorded frame, reopening the window
ffplay_process = subprocess.Popen(["ffplay", "-f", "h264", "-i", output_file])

except KeyboardInterrupt:
print("\nRecording stopped.")
finally:
# Close the serial port and the ffplay process
ser.close()


However, each time a new end-of-frame marker is detected, the ffplay window closes and reopens to show the next frame. It will flicker when transferring the video. Is there a way to display the frames in the same window for seamless playback when streaming video?

Or is there a better approach or software that is more suited for this task? I do not know where to start, so I will be glad for any hints.

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