This is a subject I posted on before, and I received a lot of valuable help from several people. At the time, I understood nothing about how audio playback works under Windows and thanks to the tips I was given, I was eventually able to fix this. I was using an old pc for testing, with DVD drive and HDMI card, and I could only get two-channel stereo from 5.1 DVD sources. Following advice, I added a separate sound card with digital output and finally got Dolby 5.1 working by running the spdif cable directly from the sound card to the receiver, though I was still never able to get 5.1 audio through HDMI. That would only play as two-channel stereo.

Now I am running up against the same problem again and I hope someone can help me further with this. Dolby Surround still works as it is supposed to if I use a DVD in the computer as the source, but I can’t get this to work from a video file and I don’t understand why. I have gone through everything and eliminated the obvious. The test file I am using is a Harry Potter recording, which was broadcast on TV2 in HD 5.1. If I play the recording on either of my two HD STBs, which double as media players, I get 5.1 sound. This is confirmed by the display on my receiver, which pops up 5 speaker symbols and DD 5.1, but I can also clearly hear it.

Yet if I play the same file on either of two computers running Windows 7, both with sound cards with optical digital outputs, I get only two channels. This happens with both MPC and VLC. If I look at the audio data in either player, it says 5.1 but I still only get stereo. I have checked the settings in Playback Devices and I am using the correct device, but I only get two channels as an option. Yet if I run the Dolby 5.1 test, all 5 speakers suddenly come up on my receiver display and I get the test tones from all five. But as soon as I play the source file, the display falls back to 2-channel stereo and that is also clearly what I am hearing.

So what am I missing here? If someone can explain to me why this is happening, and even better, how to fix it, I would be very grateful.