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• Decoding the h.264 stream from a COM port

  18 mars, par Peter

  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.

  


• python imageio.get_reader() returns odd exception

  17 août 2020, par tristan_jia

  import imageio

reader = imageio.get_reader("./t.mp4")


  


  As shown above, with python 3.6.10, it returns :

  


  >>> reader = imageio.get_reader("../")&#xA;Traceback (most recent call last):&#xA;  File "<stdin>", line 1, in <module>&#xA;  File "/home/tristan_jia/workspace/py3.6/venv/lib/python3.6/site-packages/imageio/core/functions.py", line 129, in get_reader&#xA;    return format.get_reader(request)&#xA;  File "/home/tristan_jia/workspace/py3.6/venv/lib/python3.6/site-packages/imageio/core/format.py", line 168, in get_reader&#xA;    return self.Reader(self, request)&#xA;  File "/home/tristan_jia/workspace/py3.6/venv/lib/python3.6/site-packages/imageio/core/format.py", line 217, in __init__&#xA;    self._open(**self.request.kwargs.copy())&#xA;  File "/home/tristan_jia/workspace/py3.6/venv/lib/python3.6/site-packages/imageio/plugins/ffmpeg.py", line 357, in _open&#xA;    self._initialize()&#xA;  File "/home/tristan_jia/workspace/py3.6/venv/lib/python3.6/site-packages/imageio/plugins/ffmpeg.py", line 430, in _initialize&#xA;    shell=ISWIN)&#xA;  File "/usr/lib64/python3.6/subprocess.py", line 729, in __init__&#xA;    restore_signals, start_new_session)&#xA;  File "/usr/lib64/python3.6/subprocess.py", line 1364, in _execute_child&#xA;    raise child_exception_type(errno_num, err_msg, err_filename)&#xA;OSError: [Errno 8] Exec format error: &#x27;/home/tristan_jia/.imageio/ffmpeg/ffmpeg-linux64-v3.3.1&#x27;&#xA;&#xA;</module></stdin>

  


  I searched everywhere but haven't seen any similar questions. The script runs on Opensuse Leap 15.1, is it related to the system I use ?

  


• FFmpeg returns' Output must be specified' when it has been acknowledged

  28 juillet 2019, par Syed Shah

  Here’s my command in python :

  ffmpeg -i concat:803.ts|804.ts|805.ts -c copy output.ts

  When I run the command it opens the output but it doesn’t save the file to the directory.
  I run the command in FFmpeg and it gave the same result - it opened the output but it gave me this error at the end :

  At least one output file must be specified

  I don’t understand what I did wrong as I specified the output clearly, I already checked for solutions but most of them are suited to OP’s needs