[noggin]

OK. I don't get consistent results:

Dolby True HD
hd_dthd_5.1.mkv plays back either with nasty digital noise (and the receiver reporting PCM 2.0 192kHz) or silence (and the receiver reporting Dolby True HD)
hd_dthd_7.1.mkv does the same - usually I get digital noise, but sometimes silence.

DTS HD-MA and HRA
hd_dtshr_7.1.mkv, hd_dtsma_5,1 and 7.1 all play back with silence.

DTS 96/24 and DD+
hd_dts9624_5.mkv plays back with 96KHz 24 bit 5.1 DTS audio no problem.
loreal_eac3_test plays back with DD Plus audio no problem.

At no point have I got DTS HD MA/HRA or Dolby True HD to deliver audio. I will reboot my amp just in case it has got confused.