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[SeaDrive]

I just found all of the info regarding enabling TrueHD sound in MC19. I have an Nvidia GTX-760 which does support DTS and TrueHD. I have some M2TS files with TrueHD that play the TrueHD stream in PowerDVD so I know that the format is in the files. I have configured MC to use my HDMI (WASPI) as the Audio source and bitstreaming is turned off. All other DSP features are disabled as well. When I play the file my receiver displays the audio as PCM. However, if I enable Bitstreaming the receiver shows the audio track as TrueHD. With bitstreaming turned off I look at the Audio Path and it shows the input as 48K 24 Bit 8 Channel True HD. There are No changes listed and the output format is 48K 24 bit (padded) 8 channel using WASPI (direct connect).

Why would the output not display on my receiver? Is the PCM display the same as TrueHD? I would rather not use bitstreaming because I want to use the VideoClock feature in MC. FYI, I did copy the dtsdecoderdll.dll to my Windows\Syswow64 folder. The file that I have is dated 4/26/13 but it seems to crash MC so I am using a file dated 2/11/09. How can I tell if I have the correct file or even if the file is being used? II rename the  I dont see any difference so I suspect that may be my issue.  

[6233638]

Dolby TrueHD is a container for PCM audio - just like DTS-HD, FLAC, ALAC, WAV, AIFF etc. are also containers for PCM audio.
 
Media Center needs uncompressed audio for processing, so it needs to be decoded from the losslessly compressed TrueHD format to uncompressed PCM.
 
This uncompressed PCM audio is exactly the same as the audio which was inside the TrueHD container format, but because it has been removed from the TrueHD container, your AVR has no way of knowing it was originally a TrueHD track.
 
 
Bitstreaming will light up the TrueHD or DTS-HD indicator on your AVR because Media Center is not doing any processing on the audio - it just passes it on in its compressed state, instead of decoding it first.

[SeaDrive]

OK. That's pretty much what I thought. However, I'm wondering why I get the same output whether I have the dtsdecoderdll.dll present or not.

[glynor]

Just to be clear, "passing through" DTS, DTS-MA, Dolby Digital, and Dolby TrueHD (among a few other formats) is called bitstreaming.  If you have bitstreaming disabled, MC outputs PCM (which is decoded, full-quality audio like a wav file).

It doesn't make any difference "quality wise" if you have MC decode the TrueHD stream (thereby sending PCM to your receiver) or if MC passes through the TrueHD stream (which is called bitstreaming) and then your receiver decodes it to TrueHD.  So long as both do a competent job decoding the format (which MC does, I can't speak to your receiver), then you end up with the same result.

However, if you let MC do the decoding:

1. It is easier and often less trouble-prone.
2. It allows MC to apply room correction and other DSP effects to the audio.  When you bitstream, it is not decoded at all, so MC can't apply any of its smarts.
3. MC generally does a better job with audio/video sync than your receiver will (and it has more tools to do so, with the processing power of a modern PC at its disposal).

If you let your receiver do the decoding:

1. It will light up the pretty light on your receiver.

Up to you.  I've actually waffled back and forth, but only for convenience purposes.

dtsdecoderdll.dll present or not.

That dll is only required to support DTS-MA decoding from within MC.  It has nothing to do with Dolby's format, which MC supports natively.

[SeaDrive]

Yes, I understand. But I can definitely tell a slight difference in the audio quality. I am decoding with a high end Pioneer Elite receiver so it does seem to make a difference. Here is an interesting twist. I downloaded and installed Arcsoft TMT 6 and copied the newer dll that was installed with TMT to the Plugins folder. After installation I now have TrueHD sound and the difference is much more pronounced over the PCM from earlier. I'm thinking that the dll may have dependencies that needed to install with TMT.

[Hendrik]

The DLL is only for DTS-HD MA, it has absolutely NO impact on TrueHD. You must be hearing things.

In any case, both DTS-HD MA and TrueHD are lossless formats, which means as long as the decoder works properly, you'll get the exact same PCM.
If you think one decoder sounds differently, it'll probably apply some sort of processing, or have different volume when doing Bitstream decoding - because difference in volume can make you think its different quality.

[SeaDrive]

For some reason, after installing the full TMT6 application AND placing the dll in the LAV folder the format has changed from 48K to 192K and is showing as TrueHD instead of PCM. That is the only change that I made. You don't really have to be an audiophile to hear the difference between 48K and 192K.

[6233638]

Something else has caused this change (it sounds like you enabled bitstreaming) this is not the result of using the DTS decoder with LAV Audio.

[glynor]

The DLL is only for DTS-HD MA, it has absolutely NO impact on TrueHD. You must be hearing things.

In case you didn't know, Hendrik wrote (and still writes) LAV, so he'd know for sure.