Can't use Dolby TrueHD for stereo SPDIF?

Kuripakk

Newbie Joined: Aug 13, 2015 17:41 Messages: 3 Offline

Solved by

Aug 18, 2015 19:58

So I've recently built a new Win10 HTPC and was wondering if it wasn't perhaps time to take a look at upgrading PowerDVD to the latest version. I've downloaded the trial of 15 and so far I'm pretty impressed with the speed of the application when loading Blu-rays and so on, but there's still one problem I haven't been able to figure out:

On my new build I have a USB stereo DAC/headphone amp connected, a Fiio E10K, apparently it uses SPDIF and is capable of up to 24bit/96kHz stereo audio (it doesn't decode any formats though). On discs with LPCM or DTS-HD MA I have no problem getting out LPCM stereo 24bit/48kHz (according to the information display in PowerDVD) which is what I want, however on titles with Dolby TrueHD it refuses to use the HD audio, it always just switches to the core DD track.

I remember reading something about PowerDVD having to downsample HD audio on unprotected audio paths, but surely that doesn't mean that it can't utilize the HD audio at all? And if that's really the case then how come it works for LPCM and DTS-HD MA tracks?

All I want is for PowerDVD to downmix the 5.1/7.1 HD audio (including LFE) into 24/48 stereo and output that over the digital out, is this not possible with TrueHD titles? It's literally the only thing keeping me from upgrading. Thanks.

This message was edited 2 times. Last update was at Aug 18. 2015 20:27

stewart_pk

Member Joined: Jan 10, 2014 06:36 Messages: 130 Offline

Aug 18, 2015 22:31

A couple of things, how do you know it's using the core DD track rather than the TrueHD track?

Also I don't think PowerDVD does any LFE mixing when downmixing 5.1/6.1/7.1 tracks to stereo regardless of audio codec. I think the LFE (.1) channel is ignored. This could be verified with one of those surround sound test discs.

Kuripakk

Newbie Joined: Aug 13, 2015 17:41 Messages: 3 Offline

Aug 18, 2015 23:33

If you right-click on the window and select "Show information" it'll display a box with video and audio input/output information.

On LPCM and DTS-HD MA tracks it'll show those tracks after "Audio" and after "Output" it'll show LPCM 24/48 2 channel (or whatever bitdepth/rate the track is in, it even outputs the 24/96 track of the Baraka Blu-ray.) On TrueHD tracks however it'll always show Dolby Digital 640 as input and a downsampled LPCM 16/48 as output.

PowerDVD can do LFE downmixing, at least for analog out, but for whatever reason they've hidden the option. Some versions ago (11? 12?) there used to be a checkbox in the audio settings to send the LFE channel to the speakers, but this was later removed. You can still enable it through the registry, somewhere under HKCU/Software/CyberLink/PowerDVD there are a few "LFEON" keys that can be switched to 1.

I'm not sure it does anything for me with this SPDIF output though, since there are no settings at all for it I'm not completely sure if it's PowerDVD downmixing the tracks or if there is some kind of built-in downmixing in the OS.

This message was edited 1 time. Last update was at Aug 18. 2015 23:33

stewart_pk

Member Joined: Jan 10, 2014 06:36 Messages: 130 Offline

Aug 19, 2015 00:18

Thanks for your info. I use two channel SPDIF as well as I only have a stereo setup. I would like to get hold of one of those surround sound speaker test programs that can be found on DVD/Blurays for testing.

I actually use JRiver's WDM driver sending decoded 5.1/7.1 PCM from PowerDVD to JRiver. I have JRiver configured to down-mix what it receives to stereo including the .1 LFE channel. The final stereo down-mix is then outputted via SPDIF to my external DAC.

Kuripakk

Newbie Joined: Aug 13, 2015 17:41 Messages: 3 Offline

Aug 19, 2015 06:08

Thanks for the tip about the JRiver driver, I'm going to try it out and see if it works.

Here is a DD 5.1 test file you can use to see if the LFE is being included in the downmix. I tried playing it through MPC-HC while disabling the internal mixer in the LAV filters and I still got a downmixed stereo output including the LFE, so I guess my setup must also be capable of downmixing further down the line in the drivers or something.

stewart_pk

Member Joined: Jan 10, 2014 06:36 Messages: 130 Offline

Aug 19, 2015 07:52

Holy crap, I found a test file from https://www2.iis.fraunhofer.de/AAC/LFE-SBR.mp4 and LFE was not playing through PowerDVD direct or via the JRiver WDM driver. So all this time I've been missing out on LFE and not even knowing it, although I always questioned it in the back of my mind.

So I found the registry entry you mentioned, changed it from a 0 to a 1 and it works! Thank you very much sir.

stewart_pk

Member Joined: Jan 10, 2014 06:36 Messages: 130 Offline

Aug 19, 2015 08:46

And I can confirm that Dolby TrueHD is being decoded as I tried a Bluray disc and under information it said "Audio: Dolby TrueHD 5.1". Although output is 16 bit and not 24 bit as under information it said "Output: LPCM 48KHz/16bits 2 Channels". I hope this helps.