alsasrc/input-selector combo broken in Gstreamer 1.2.0

[Thomas Roos]

I am using an input-selector element  to select one of two microphone
inputs delivered as a stereo stream by alsasrc.
This worked fine in Gstreamer 0.10.36, but seems to be broken in
Gstreamer 1.2.0.
After switching the sink of the input-selector, the pipeline produces
silence for some time (running-time of pipeline ?)
until finally the live data are to be heard again.

The behaviour can be reproduced with the minimal program attached,
which produces 5sec of silence after switching.

Everything works as expected when alsasrc is replaced by a
2*testsrc/interleave combo.

here you can find a minimal test program:

https://dl.dropboxusercontent.com/u/912792/alsasrc-input-selector-test.c