alsasrc vs pulsesrc clocks and timestamps

[mattes]

There seems to be a difference in timestamp behaviour depending on the audio
source plugin used.  

I used the following pipeline:
  alsasrc -> audioconvert -> faac -> qtmux -> filesink

I start a recording and after X seconds I switch to PAUSE.
Waiting Y seconds I switch to PLAYING again, to resume the recording.

I noticed that the timestamps do not reflect the paused 'Y' duration.
Instead timestamps continue as if Pause never happened.
The timestamps after the pause continue at Z time (= X+Y seconds).
This results in an issue some player (demuxer) can't tolerate, when
the timestamp jumps from X to Z.

I tried to use different clocks but that does not make difference for me.

Next, I replaced the audio source with 'pulsesrc'. Surprisingly this behaves
different. When pausing the recording and resuming after Y seconds, the
timestamps continue in order without the (Y second) jump.

What can be done to make 'alsasrc' to do the same as pulsesrc does,
when switching from pausing and playing again?

Mat