Originally Posted by jim.bennett
So to summarize what I think I have understood after reading through the thread, the Geforce 8200 IGP supports 7.1 LPCM over HDMI. Bitstream output is NOT supported.
However you still cannot get full (not downsampled) decoded Dolby TrueHD or DTS HD-MA from the PC until a software player can decode it and send it without downsampling.
PowerDVD from what I understand decodes them but downsamples the output. Are there any software players that can decode them and NOT downsample them for output as LPCM over HDMI?
More precisely, unless
the audio path is protected (and in fact the protected audio path is nonexistent
right now in PC),
- AACS-encrypted contents must be downresolutioned to 16-bit/48kHz.
A Licensed Player shall not pass, or direct to be passed Decrypted AACS Content to a digital output except:
1.4.1 A digital output of audio, or of the audio portion of other forms of Decrypted AACS Content, in compressed audio format (such as AC3) or in Linear PCM format in which the transmitted information is sampled at no more than 48 kHz and no more than 16 bits.
1.4.2 An output delineated in Table D1, AACS Authorized Digital Outputs, in accordance with any associated restrictions and obligations specified
- Unencrypted contents (including contents decrypted by AnyDVD HD) need not be downresolutioned, but as a matter of fact are downresolutioned to 16-bit/48kHz by PowerDVD. This a bug CyberLink acknowledged (PowerDVD audio downsampling explained
) and has not been fixed yet (?).
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.