[FFmpeg-user] Video overlay of several network inputs using ffmpeg

[Hristo Ivanov Ivanov]

Hi,

I am trying to overlay several network inputs(udp streams). The command I
have so far looks like this:

.\ffmpeg.exe -threads auto -y -i input0 -i input1 \
   -filter_complex
"[0:v]scale=1920x1080[v0];[1:v]scale=480x270[v1];[v0][v1]overlay=1440:810[v2]"
\
   -map [v2] -map 0:a -c:v libx264 -preset ultrafast -c:a copy output.mp4

When input0 and input1 are files the resulting output is correct, on the
other hand, when the inputs are udp streams the resulting output is not
correct, the video freezes most of the time.

The file inputs are generated from the udp streams, using the following
command:
.\ffmpeg.exe -threads auto -y -i "udp://@ip:port" -c copy -f mpegts
input1.mpg

Why is the above command not producing good ouput for upd streams?
What are the differences between the original stream and the dump of that
stream for `ffmpeg.exe`.
How can it be fixed?

Thanks.