Output Video Contains Blank Frames. #1758

I am new to PyAV and trying to process an input container (highway.mp4, 15.1MB). I have attached the codec information extracted from VLC as an image.

My goal is to extract packets from the input and directly mux them into an output container (test_output.mp4) with a custom configuration (codec, FPS, height, width, etc.), without using the template argument in add_stream. However, the output video is generated with blank frames while retaining the same size and duration as the input.

I have tried different codecs and added various parameters, but the issue persists.

Additionally, I encountered another issue: the video_stream object is non-serializable.
Environment

Python Version: 3.8.19
Ubuntu Version:

Distributor ID: Ubuntu  
Description: Ubuntu 24.04.1 LTS  
Release: 24.04  
Codename: noble  

PyAV Version: 10.0.0

Code Snippet

import av

input_ = av.open("highway.mp4")
output = av.open("test_output.mp4", "w")

in_stream = input_.streams.video[0]
if 0:
out_stream = output.add_stream(template=in_stream)
else:
# codec_name = in_stream.codec.name
codec_name = "mpeg4"
# codec_name = "libaom-av1"
# codec_name = "mp4v"
# codec_name = "avc1"
# codec_name = "libx264"
out_stream = output.add_stream(codec_name, in_stream.average_rate)
out_stream.width = in_stream.codec_context.width
out_stream.height = in_stream.codec_context.height
out_stream.pix_fmt = in_stream.codec_context.pix_fmt

for packet in input_.demux(in_stream):
if packet.dts is None:
continue
packet.stream = out_stream
output.mux(packet)

input_.close()
output.close()

Expected Behavior

The output video should contain valid frames, not blank ones.
The video_stream object should be serializable.

Actual Behavior

The output video has blank frames with the same size and duration as the input.
The video_stream object is non-serializable.

Steps Taken to Troubleshoot

Tried multiple codecs (mpeg4, libaom-av1, mp4v, avc1, libx264).
Tested different parameter configurations.
No success in resolving the blank frame issue.

Request for Help

What could be causing the blank frames in the output?
How can I serialize the video_stream object?
Any suggestions or corrections to my approach?

Thanks in advance for your help!