bit-tech.net

PowerDVD audio downsampling explained

PowerDVD audio downsampling explained

PowerDVD Ultra doesn't yet provide full TrueHD or MasterHD audio but will come 2008.

Since publishing our preview of Gigabyte's GA-X38T-DQ6, a board that uses the Realtek ALC889a codec and supports HDCP content encryption, it became apparent that this doesn't matter for Cyberlink's PowerDVD Ultra, as the software appears to downsample all audio to 48KHz / 16-bit (DVD quality), regardless of whether there is content protection in place or not.

So, what's the point of HD quality audio if you're never going to get it? Is this the fault of Cyberlink, Microsoft, or is it simply sound card drivers? We talked to Cyberlink PowerDVD Product Manager, Louis Chen, to get to the bottom of it.

When asked why PowerDVD downsamples HD audio from both Blu-ray and HD DVD discs to 48KHz / 16-bit, Chen responded by saying that "digital output without protection is not possible due to AACS requirement. Digital and analogue output with protection (HDMI) is also not possible due to lack of an internal secure audio path in a Windows PC.

"We are currently working with Realtek to support their proprietary interface for encryption of audio bus. Once completed, we will not longer need to downsample the audio. This will be provided for free to end-user for upgrade."

This didn't really clear up the downsampling situation though because, as far as we're aware all audio, regardless of encryption, is downsampled. We therefore pressed Chen to clear up the speculation. "I think this is a mistake," he said, "we never intended to pass this message. I think there might be some bug in our program that downsamples everything. That is not our intent. We only need to down-sample premium content (AACS, CPRM, etc)."

This prompted us to ask whether there is a requirement for AACS in a PC when a disc or file is not encrypted. Chen told us that the unencrypted scenario is not mandated by AACS so shouldn't be included in the downsampling.

We inquired further about the "secure internal audio path": is this because of Microsoft not providing one and/or sound card companies not providing a compatible driver? Chen informed us that there isn't an industry standard (defined by Microsoft or someone else) that makes the encryption/decryption path between software and audio driver secure. Cyberlink have to enable one chip after another which takes a considerable amount of time working with sound card providers, Microsoft and checking that it satisfies the AACS mandate.

The Realtek ALC889a is the only audio codec that advertises HDCP encryption, therefore allowing the full-HD audio, however Chen implied that other sound cards will also be capable. On inquiry Chen told us that Cyberlink is working with Realtek and other vendors like C-Media, ADI and Creative at defining a method to protect HD Audio, however as stated this takes time to enable. Once this path is secure, PowerDVD can output (analogue) in full resolution.

Finally we asked when can we expect the update to arrive, but Chen hesitated to give us a firm date, hinting that it will be sometime in 2008. This is understandable considering the many factors outside of Cyberlink's control.

Regardless of the no protection downsampling "bug" that currently exists in PowerDVD Ultra, it seems that those who have pushed AACS on us are progressively killing the home theatre PC industry. It seems ironic considering the Blu-ray and HD DVD specfications offer more PC-esq interactive features and CE devices are becoming less one function dumb boxes and more like the multifunction PC's we use every day.

The PC already doesn't support HDMI 1.3 because it cannot handle the 36-bit colour depths required for Deep Colour, since no Microsoft OS, including Vista, can recognise more than 24-bit RGB colour. It's now also been shown that you can't even do protected high-definition audio either. So, is high definition video enough for you considering you can't get all the extras that a consumer electronics device has, or is it yet another excuse to ignore it completely? Let us know your thoughts in the forums.

12 Comments

Discuss in the forums Reply
samkiller42 8th October 2007, 16:41 Quote
Ouch, that hurts me after spending 50quid on it. It was a kick in the teeth when powerdvd told me i coudn't watch HD films on my 30" for some sill reason, that too was a kick in the teeth:(

Sam
Joeymac 8th October 2007, 18:12 Quote
Oh course.. the funny thing is that any of the HD DVD and Blu-Ray discs that have been decrypted (nearly all of them) can be downloaded from various sources and the HD audio will work without the "protected audio path"...which will probably require a new soundcard or something.
So pirates and "non-dmca conformists" will get a better deal than normal customers. Yet again.
leexgx 8th October 2007, 19:53 Quote
Load up Anydvd HD/BD all content should be uncrypted and no down sampleing on the sound unless its just an drop every thing
Kipman725 8th October 2007, 20:26 Quote
bleh more marketing bolocks eyncrpted audio path indeed... why is a sample rate higher than 48kHz needed anyway. A sample rate of twice the maximum frequancy to be sampled is all that is needed for a PERFECT reproduction and the maximum freq humans can hear is aprox 20kHz. As for 16 bits that gives us 65536 values of loudness which is also enough. The only reason you would need more is if you wanted to do some funky editing which the content restrictions prevent.

you know these DRM restrictions are making my life very inconveniant as somoen interested in electronics and audio gear even if I don't want to watch there films by restricting access to I/O and IC's and its getting on my nerves.
Max Spain 8th October 2007, 20:29 Quote
Read this paper from M$. It describes several DRM tech that have been/will be implemented into Vista. One of them is PAP (Protected Audio Path) which is probably what Cyberlink is hinting at. This is essentially PVP (encrypting data over PCI-E bus, supported on certain Nvidia 8000 series cards) but instead of video, you are encrypting audio. Vista already contains PUMA (Protected User Mode Audio) but apparently that isn't good enough

Enjoy the Windows Vista Experience :'(
perplekks45 8th October 2007, 20:51 Quote
So this means everybody who bought Vista to watch HD stuff on his PC is screwed and will have to wait for Vienna (does it support 36bit color depth at all?)? Yea, sure it's that... no marketing... no no, that's not sarcasm over here. Honestly! :|
Renoir 9th October 2007, 05:20 Quote
First off hats off to you Rich for chasing this matter up after our discussion in the gigabyte thread. Bit-tech is my number 1 tech site because of the time you guys take to answer questions in the forums and do things behind the scenes to get the answers the community asks for. Just thought I'd let you know that these things don't go unnoticed and are much appreciated ;););) Right that's enough brown nosing from me on to the matter at hand.

The confirmation of the "bug" that downsamples all high res content indiscriminately is rather concerning given how much they tout their audio support in their marketing. A bit dishonest if you ask me.

The HTPC has such potential but it's DRM issues like these that stop it from reaching that potential. Take this thread for example where people have been crying out for an HDMI solution that supports multiple channels of high res audio and even the multiple channels from games in a way that maximises fidelity and fully takes advantage of existing technology (HDMI's been around for a good while now). The current implementations of HDMI on pcs leave a lot to be desired as they are effectively just S/PDIF over HDMI. There's no technical reason that I know of that prevents the hardware manufacturers from providing a non-handicapped HDMI implementation. It seems to all be down to an issue of DRM which screws everything up and really limits what a great HT platform the pc can be. Rant over.
Bladestorm 9th October 2007, 07:00 Quote
For me its yet another reason to ignore it completely.
HourBeforeDawn 9th October 2007, 07:33 Quote
well my only beef is that I got the GIGABYTE GA-G33M-S2H for its advertised onboard-video playback that supports full 1080p and then after I get the board and start reading the fine print it states does not support playback of blu-ray or hd-dvd.... then whats the point >_< so bummed out, contacted Gigabyte and they states that they cant do anything until Intel released a driver that will support it >_< ugh... so I will end up having to get a dedicated graphics card after all that can support it >_< but now to hear this audio issue to so much for a HTPC with Blu-ray and hd-dvd play back.
swin70 16th July 2009, 22:35 Quote
Does this scenario still hold true? Can a HTPC still not output full resolution audio and video?

I am in the throws of building an HTPC as the centre of my Media home. This will be connected to a Pioneer Kuro 42" Plasma and a Yamaha DSP-AX863 AV Receiver, which has a 5.1 surround speaker set-up. I was looking at integrating a Blu-ray player into the system, but if the system can't output full resolution audio and video, all of a sudden I'm beginning to think this might not be the way to go.

How are things progressing on this front?

Cheers.
thehippoz 16th July 2009, 23:57 Quote
really a non-issue.. I've worked with digital audio for a long time and 48k stereo is overkill- music back in the day on cd was released at 44.1k 16-bit, you can't even hear frequencies that high (I'd say frequencies around 32khz with really sensitive ears are possible- the rest your getting into dog whistle land)

I've generated sine waves up in those frequencies and was unable to hear them with a good set of tweeters.. your not missing out on anything
swin70 17th July 2009, 00:42 Quote
Whilst I accept that audio frequencies above a certain level (commonly 20kHz) are regarded as in-audible to the human ear, and the 192kHz sampling is capable of reproducing much higher frequencies (192/2)kHz, it also means that "normal" frequencies are sampled more often gaining a higher degree of accuracy.

The debate of this one has and will go on for years. Certainly, in audio test, i have heard differenced between 48 kHz and 96 kHz audio - how this is possible I don't know - but many other people feel/hear the difference too. Grated I couldn't tell the difference between 96 and 192 kHz!
Log in

You are not logged in, please login with your forum account below. If you don't already have an account please register to start contributing.



Discuss in the forums