Seeking a pipeline containing concat only seeks the latest source

Submitted by Jay Yang

Description

Created attachment 355384
Code to reproduce the bug

It seems that concat simply forwards the seek event to the current sink pad, and so if we try to seek to the beginning of the pipeline it only seeks part of the way.

I've attached a file that demonstrates the issue. It needs a test.ogg file that runs for 2 minutes. The code runs a pipeline consisting of two copies of test.ogg concatenated with concat. It runs the pipeline for 3 minutes and then tries to seek to the start. I would expect then the code to run for a total of 7 minutes, instead it runs for 5 minutes.

I'm on 1.10.5

Attachment 355384, "Code to reproduce the bug":
bug.c

Version: 1.10.5