Playback freeze when seeking with input-slave

Using latest git master. commit 946a8e91 Date: Sat Jun 27 17:51:05 2009 +0300

When playing a video file + audio file, seeking will sometimes cause playback to freeze or to become very slow.

To test, download these small files:

1. http://samples.mplayerhq.hu/MPEG-4/Concession_LAN_800k.mp4
2. http://www.nch.com.au/acm/11k16bitpcm.wav

Then run:

vlc Concession_LAN_800k.mp4 :input-slave=11k16bitpcm.wav

Seek a bit forward, and then seek backwards. Playback will become very slow (Status bar shows "Buffer: 0%").

Note that there is no need to set the alternative audio track as "active" for the problem to happen.