I would like to use gstreamer to play multiple sources (for instance two video files) simultaneously using a single pipeline but each video starting from a different position, for instance first video from the beginning and the second from the middle. Could someone guide me on how to achieve it?

Simplifying, my pipeline is an equivalent of:

gst-launch-1.0 \
uridecodebin uri=file:///Users/tmikolaj/Downloads/videoalpha_video_dancer1.webm ! videoconvert ! autovideosink \
uridecodebin uri=file:///Users/tmikolaj/Downloads/videoalpha_video_dancer1.webm ! videoconvert ! autovideosink

, but created programmatically.

Obviously, simple seeking the pipeline seeks two files at once. I was trying to register a probe of the GST_PAD_PROBE_TYPE_EVENT_UPSTREAM type from inside the pad-added signal callback of the uridecodebin element. Inside the probe I wanted to catch the GST_EVENT_SEEK event and drop it for the first video. However, it seems that dropping the SEEK message leaves pipeline in a PAUSED state and even an explicit state change to PLAYING does nothing. Does anybody has some hints on how to solve that problem?