we discussed this in this thread: http://www.vdr-portal.de/board…?postid=382390#post382390
Try to mute the sound (speaker off) . But it could be, that the patched kernel does not allow digital output. Until this is fixed( wanted: a new Nexus- CA patch ) you should use an older kernel.
http://drseltsam.device.name/vdr/linvdr-kernel-2.6.12.4.tgz is still online -with dvb-drivers from mid-august