Author Topic: A TBG Summary: The ins and outs of passing high-res audio from your HTPC  (Read 3472 times)

Ari Altman

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A reader recently asked us how he could pass lossless Dolby Digital True Audio or DTS-Master Audio streams from an HTPC to his older receiver, which couldn't process these newer lossless formats. He thought about using digital optical cables, potentially running HDMI to his TV and then digital optical from the TV to his receiver, as his TV was newer than the receiver and could handle the lossless formats.

So, long story short, once you introduce any digital optical cables into your system, you lose any chance of passing a lossless data stream. That's because these cables, along with digital coax cables, do not have sufficient bandwidth to carry a lossless signal. In other words, if you have an HTPC, even with older AV equipment, as long as HDMI is an option (i.e., post-2006 receivers and TVs), it's the one and only cable you should use. The sole exception is if you're using an add-in sound card like the Creative Sound Blaster Z, which is limited to older compressed formats, but has enhanced processors to make these formats sound better versus what your on-board motherboard or video card sound processors can achieve. This is great for games and high-end audio, for instance, which don't use DD:TA or DTS-MA.

If you have a newer receiver (say, post -2010), none of this should worry you, as it can process the lossless bitstream (and that is what you should use, because on a good AV system, the difference between lossy and lossless is significant). Keep in mind that DD:TA and DTS-MA are backwards compatible, so they always include an older data stream that can be used by DD and DTS receivers. If, for instance, you're watching a Blu-Ray on your HTPC and it only has a DTS-MA soundtrack, you'll get DTS sound output to your pre-DTS-MA receiver via HDMI, or alternatively through a sound card using digital optical out.

And for those who like to tinker, there actually is one way to get lossless formats to a pre-lossless AV receiver, and that is by converting the stream at the source to linear PCM (LPCM), rather than bitstreaming it to the receiver, where it will be down-sampled. Now, this requires jumping through some software hoops on the HTPC side, because Windows cannot by default convert these lossless formats to LPCM. To learn more about what's required in terms of software to send a lossless LPCM signal via HDMI to pre-lossless receivers, see this external blog post.
« Last Edit: April 26, 2015, 08:13:57 AM by Ari Altman »

Ari Altman

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Re: A TBG Summary: The ins and outs of passing high-res audio from your HTPC
« Reply #1 on: November 08, 2015, 10:56:21 AM »
One of our readers had a great question about setting up Blu-Ray playback on a high-powered Home Theater/Gaming PC similar to a reader build showcased in The TBG Gallery. We thought we'd pass it all along, followed by our response:

"First, thanks so much for creating and maintaining such a great website. I switched to Mac a long time ago for issues of sanity in my every day work life, but I am looking to build a high-powered PC for my home theatre to play games and blu-rays.  I was hoping you could answer two questions for me:
 
1.)  Is there room to insert a blu-ray player/writer?
2.) Do you think that this setup would be just as good or better than a good standalone blu-ray player (i.e. Oppo-105)?  This is with respect to both sound and video output.  My video would go directly to my Samsung 4K TV, but the sound would go through my beastly Arcam AVR450 receiver."


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Here's our response:

"Yes, you can definitely equip this case with a Blu-Ray Drive, like the LG 16x Burner.

Just note that if you want to play Blu-Ray movies, you'll need a full version of Cyberlink software or other playback software. You'll also need to supply your won software for burning. Hope that helps. Let me know if you decide to go ahead with the build!

Being a bit of a HiFi guy myself, I simply trust dedicated solutions more than PC solutions for Blu-Ray playback. So I use an Oppo BDP-103D.

I've actually never done a back-to-back comparison against my HTPC, which I use for streaming, but I'd guess that Oppo's audio processors in particular will be much better than what you'd get with a PC, unless you went with a high-end sound card like the Sound Blaster ZxR:
 
But that creates a new problem when using an HTPC for Blu-Ray playback: getting lossless sound. Video output needs to go through HDMI (preferably a GeForce GTX 900-series card with HDMI 2.0 for 60Hz/4K output), but that constrains you to the GeForce card for sound output as well, as add-in sound cards don't have HDMI connectors and therefore don't do lossless. You'd therefore want to use the GeForce card and select bitstream to have your receiver process the sound from the video card. And that can be complicated, see this thread.

The last piece of the puzzle is the software, and you'll never find PC BD playback software that is as elegant as popping a disc in and pressing play.

Ultimately, you'll have to decide for yourself whether integrating everything into your HTPC is worth the trouble. It may very well be, but I'm plenty happy with my Oppo!"
« Last Edit: November 08, 2015, 11:57:12 AM by Ari Altman »