PowerDVD audio downsampling explained

October 8, 2007 | 15:06

Tags: #down #hd #hdcp #powerdvd #sample

Companies: #cyberlink #ultra

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.
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