I've had an issue with audio dropping off certain programs when watching Freeview HD. I use an HDMI lead from my HTPC to my TV, using spdif bridge from Audigy 2 ZS audio card to my 9800 GT in the HTPC. Usually audio and video work great, but for certain DVB-T TV programs. TV3 is where it pops up (though it may be an issue for other channels), the common thread is the programs where I have no audio are broadcast with Dolby Digital Plus or E-AC-3. After some investigation, looks like spdif can't handle this codec - http://en.wikipedia.org/wiki/Dolby_Digital.

text from site: "E-AC-3, more commonly known as Dolby Digital Plus, is an enhanced coding system based on the AC-3 codec. It offers increased bitrates (up to 6.144 Mbit/s), support for more audio channels (up to 13.1), and improved coding techniques to reduce compression artifacts. It is not backward compatible with existing AC-3 hardware, though E-AC-3 decoders generally are capable of transcoding to AC-3 or DTS for equipment connected via S/PDIF. Only the discontinued HD DVD system directly supported E-AC-3, though Blu-ray disk offers E-AC-3 as a option to graft additional channels onto an otherwise 5.1 AC-3 stream."

I'd be interested to hear from anyone who has come across the issue before and has solved it. Any suggestions also welcome of course. I'd like to avoid installing various codecs if possible as my current setup is working great aside from this issue.