As I have noticed so many threads asking how to get HD audio from Blu Rays and HD-DVD's out of a HTPC, I have decided to create this little guide abut how to get the full proper potential of Dolby TrueHD, Dolby Digital Plus and DTS HD Master; as well as additionally explaining why you may not be able to get it on your HTPC.
I hope that this will clear up any issues people have about this problem so to reduce the amount of threads asking pretty much the same question.
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1. Why HD Audio does not Automatically come out of every HTPC?
There are two main reasons for this:
Lack of HDMI
HDMI is the only way to get HD audio as bitstream or LPCM. Mostly this is because of bandwidth, (Coax and Optical S/PDIF don't have enough) so HDMI is needed if you want to send more than two channels to your reciever. Just as bad, there is the slightly irritating problem of High Definition Copy Protection (HDCP) which has been forced on Blu Ray disks and HD-DVD's by the major studios in an attempt to curb piracy of HD media. This will be discussed below.
HDCP
HDCP is IMO just a complex method of making it as hard as possible for you to get HD content.
Really though it is rather simple - both ends (i.e the graphics/sound and the monitor or HDTV/reciever) have to be HDCP compatiable, or the video and audio quality is reduced to DVD and CD quality respectively. The content is encrypted and unless both ends can understand and decode this encryption and 'handshake' correctly with each other, then it does not allow HD output.
HDCP dictates that all
digital HD content must go over HDMI version 1.3 or better (or DVI as it is related to HDMI although not many ports are HDCP compatiable). Note the use of the word
digital as HD audio and video will go fine over
analogue connections such as VGA D-sub, component and analogue audio jacks. This will be discussed in more detail later on.
Not very many soundcards are HDCP compatiable (At the moment only one type and they cost ££$$). This will be talked about below.
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2. How can I get HD Audio Then?
Well at the moment currently there are two ways of getting HD audio from a HTPC:
- Get an ASUS Xonar HDCP compatiable sound card
- Decode the Audio by Software and Output on the Analogue Audio Jacks
Get an ASUS Zonar HDCP compatiable sound card
At the moment currently, the ASUS Xonar soundcard is the
only soundcard that can output HD audio as its HDMI port is HDCP compatiable. It also has a whole host of features such as Dolby Digital Live and Dolby Headphone so it is very useful for things such as games that are not encoded in Dolby Digital and cannot be output over S/PDIF.
However with all good things there is a catch, the Xonar costs about £150 which obviously is going to set you back quite a bit, but it is curently the only way to bitstream HD audio to a reciever.
Heres a link to the Asus site for the Zonar:
http://uk.asus.com/Product.aspx?P_ID=wIxyLFT9vTWHLHk8
The method below is substantially cheaper mind.
Decode the Audio by Software and Output on the Analogue Audio Jacks
If you have a Blu Ray softare player such as WinDVD or PowerDVD then you can decode the HD audio using the CPU so it can be output over the analogue jacks to the analogue passthrough on the reciever, although you will need a soundcard or onboard soundcard with 5.1, 6.1 or 7.1 analogue outputs.
The software should automatically decode the audio, so all you need to do is hook you reciever up and you have HD audio. It can be a bit fiddily connecting up all the jacks as some will be RCA type and others stereo jack, so you will need some adaptors. Usually in my experience you don't get a jack or RCA to each channel either as they will be mixed up with each other, so refer to your soundcard or motherboards manual.
If you only have stereo outputs then look in the cheating section below for some useful tips.
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3. How to Cheat
There are a few unorthordox ways of getting HD audio:
- Downmixing HD Audio to Stereo and Sending over S/PDIF
- Using Dolby Pro Logic II on Analogue Stereo
- Stripping the HDCP (Theoretical)
Downmixing HD Audio to Stereo and Sending over S/PDIF
In WinDVD and PowerDVD at least, there is an option to downmix HD audio to stereo as this is small enough to be passed over S/PDIF to the reciever as PCM. If you look in the sound options somewhere there should be an option to do this.
Obviously this is useful if you only have S/PDIF. After it reaches the reciever you can do one of two things:
- Leave it as it is in Stereo
- Use Dolby Pro Logic II on the Audo to get 5.1 or 7.1
The first is the best option if you want just pure, great sound, but the second allows you to have it in surround once more.
The problem with the second option though is that by the time it has been transformed into all the channels, you may as well just use Dolby Digital or DTS as it will not be discrete sound and proberly will only sound slightly better.
Using Dolby Pro Logic II on Analogue Stereo
If you only have a stereo analogue output, then using the Dolby Pro Logic II as above could make it slightly better.
WinDVD and Power DVD have the option to encode the content in Pro Logic II before outputting it as analogue audio and this may inprove the surround quality if you use this option because the other channels will be matrixed into the stereo sound for the reciever to decode.
Stripping the HDCP (Theoretical)
I hear you wonder:
"If I could get rid of the HDCP then all of my problems would be solved..."
Whilst yes that would work if you don't have HDCP equipment, unfortunately for
sound it is not possible, but with
video it is. I have yet to see a HDCP stripper for sound as all the ones I have seen only do video. You won't see them advertised either as the HDCP creators and endorsers will sue the manufactuer for quite a bit.
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Anyway, thanks to anyone that reads this and I hope it helps you.
All information is correct to my knowledge, but if anything is not, discuss it below.
