[vdr] vdr-sxfe and IEC958 audio

I have a digital S/PDIF output from my VDR frontend hooked up to a decent home amplifier and surround speakers.

In the past I've had no problems using this via a vdr-sxfe frontend both for stereo MPEG-2 audio, as well as for 5.1 AC-3 on HD channels.

audio.device.alsa_default_device:plughw:0,1 audio.device.alsa_front_device:plughw:0,1 audio.device.alsa_passthrough_device:plughw:0,1 audio.device.alsa_surround51_device:plughw:0,1 audio.output.speaker_arrangement:Pass Through

However, recently (perhaps due to a kernel / alsa update?) I've found that I have to execute `iecset audio on` (to make analog MPEG-2 audio work) and `iecset audio off` (to make AC-3 passthrough work).

Any idea why this might be?