Trouble Muxing Video and Audio from Separate Streaming Sources

[3735943886]

I'm having trouble muxing video and audio from different sources.
In my situation, the video comes from a UVC device (using V4L2), and the audio comes from ALSA. Both of them are infinite streams.

I wrote the following code:

input_container_a = av.open("hw:0,0", format="alsa", options={"channels": "1"}, mode="r")
input_container_v = av.open("/dev/video0", mode="r")
input_stream_a = input_container_a.streams.audio[0]
input_stream_v = input_container_v.streams.video[0]

output_container = av.open(rtsp_url, mode="w", format="rtsp")
output_stream_a = output_container.add_stream("aac", rate=48000)
output_stream_v = output_container.add_stream(template=input_stream_v)

a_packet = next(input_container_a.demux(input_stream_a))
v_packet = next(input_container_v.demux(input_stream_v))

while True:
  if a_packet.pts <= v_packet.pts:
    output_container.mux(a_packet)
    a_packet = next(input_container_a.demux(input_stream_a))
  else:
    output_container.mux(v_packet)
    v_packet = next(input_container_v.demux(input_stream_v))

However, the code does not behave as intended.

Could anyone help me figure out how to properly mux two separate video and audio streaming sources?