HD-A2 HDMI Audio Issue?

Funny you ask, but when I first viewed V for Vendetta my receiver showed PCM96 + PLXII + MV when I viewed the TrueHD track.

The next time I put it in, it DID NOT show PCM96 + PLXII + MV on the receiver. The only time I saw the PCM96 was the first viewing of V and that was it. I don't know what happened, but I'm not imagining it.

THis is with my A2.

In the Problems thread, it was suggested that you switch your optical audio out to be PCM instead of Bitsream (even if you aren't using it).

When I did this, it now displays as PCM96 on my receiver. Give it a shot.

Hey! That did it. Now it's showing up as 96Khz on my Denon 3806. Just lik with the A1.

Why would you want to up-sample the audio through the player anyway? I would think that if the source is encoded at 48 kHz I would leave it at that rate before the DAC process.

The a1 output everything at 96Khz PCM. UNtil we get a 96Khz TrueHD track there would be no way to test this. Last Night I only checked it for a couple of minutes but didn't really notice a sound difference although I had the volume setting low. I'll have to check it this evening at a higher volume level.

I tried a couple of HD disks on my A2, and the DD+, Dolby True HD and DTS HD tracks came through in 96khz over HDMI.

But then I dropped in some SD disks and got 48khz for the DD and DTS tracks.

Dropped in Queen the game DVD, and got 96khz for the DTS96/24 track, and 96khz for the 96khz stereo LPCM track.

I also dropped in a CD and got 44.1khz.

Could be that those HD tracks really are 96khz.

The volume of the HD tracks is significantly lower than SD and CD, I think this is a known issue.

I always questioned why I was forced with 96 kHz output for HD DVD discs with the HD-A1. Just because the sampling rate is higher and like the HD-A1 doesn't mean that it's better than 48 kHz output. Up-sampling can degrade quality if done improperly. The volume difference mentioned by Doc has me questioning the quality of the up-sampling.

Good question.

The player is not creating any additional audio resolution is it? If not, it would seem that displaying 96 kHz on receivers when the the source is 48 kHz would be misleading.

Are there any experts out there that would be kind enough to explain this phenomenon?

Thanks.

Larry

Just a SWAG. Maybe 96 kHz gives less resultant clock skew (because of jitter) after the transport over HDMI? Both S/PDIF and HDMI (1.0, 1.1, 1.2a) have clock jitter issues as far as audio purists are concerned. HDMI 1.3 is supposed to address some of the jitter issues. Many like i.Link (1394 firewire) transport because it has virtually no clock jitter problems.

Dolby states that their lossless encoder currently supports up to 96/24. This does not mean that all TrueHD encodes are 96/24.

Also, I think file size readouts and insider information have confirmed that all current HD DVD movie audio encodes are at a 48 kHz sampling rate.

I am using a Pioneer Elite 72 TXVi via HDMI with the Toshiba A2 and from the start I set my player outs to PCM and am very pleased with the results. After reading about the difference with the optical jack set to bitstream I decided to try that and see if I could hear any differences and see what difference I got from the readouts. I first tried Phantom of the Opera and it sounded almost the same but not quite as good. I chose the Dolby TrueHD track and my Pioneer showed PCM period, previously it had shown 96 PCM Digital. I next tried Chicago-Earth Wind & Fire HD DVD using the Dolby Digital Plus 5.1. There was a very noticable drop in the sound quality and my Pioneer showed PCM period , previously it had shown PCM Digital but not anything about 96. The difference in sound quality on this disc really demonstrated the need to set the optical out to PCM versus bitstream if you are cabled via HDMI. It also demonstrated that even when set up this way not all discs will report 96 on my Pioneer.

MN-Rabbit,

I have the same receiver as you and have the A2 on order. Thanks for the setup information.

Hi,

I have found KMO's postings always to be instructive. Here's his take on the subject when I posed a question about upsampling to him.

Another PCM / HDMI for a dummy question(s)

Larry

Thanks. I agree with KMO; the player should not be up-sampling. With HDMI, up-sampling should be reserved solely for the receiver or pre/pro to handle before the DAC stage.


It could mean the sampling rate and bit depth as well. Don't look too far into semantics here. 96/24 encodes would take too much space for some movies. Although I have no proof, I am very confident that most, if not all, current TrueHD encodes are 48 kHz.

I have the A2 connected via HDMI to a Yammie RX-V2700 (HDMI 1.2a). I have tried changing the optical output to PCM. No change in audio is observed nor does the receiver indicate 96 khz.

Hi,

This thread might interest you.

Some Warner Titles in Dolby TrueHD 6 Channel Lossless24-bit/96 kHz

Notwithstanding the title of the thread, Marc Fishman, (FilmMixer) a professional sound mixer, made the case, in March 2006, that it's unlikely that any major studios were mixing at 96 kHz, nor would they for a long time.

Quoting from the thread:



Larry

Interesting! Would you give a technical reply to address the clock jitter issue?

Could you give a technical explanation describing the quality of the Toshiba players' up-sampler? People don't buy $2,000+ receivers or pre/pros with high quality up-sampling and DACs to have their audio hampered by poorer quality up-samplers used in inexpensive components.

I just received my HD-A2. I can vouch to Doc's finding. When the audio settings are at PCM and is output as 96 kHz, the audio from all channels is much more subdued. The 48 kHz setting, on the other hand, seems right. I can't use the 96 kHz setting because I would have to bump the volume control at much too high of a volume.

So your reply to me on the clock jitter issue is -- no answer.

As to Toshiba upsampling --- well they have a reason to do so in the 1st gen models with their 24bit/192kHz Burr Brown DACs, eight of them. The second gen A2 still has analog stereo outputs. People (audio aficionados) have been very happy with their high quality audio playback for CD's. As to the known "quality" of the upsampling -- well it is done in the digital domain with very highly rated Analog Devices SHARC DSPs for the 1st gen. As an engineer I am at a loss as to how "inexpensive components" cause a poor upsampling job to be done in the digital domain.

Could you provide proof that HDMI is a poor transport in terms of clock jitter? Here's just one article explaining how up-sampling in general, and outside up-samplers and oversamplers, can degrade quality for SPDIF transports when the source is of high quality. This is the kind of thing that raises questions in my mind.

I just want to learn.

Clock recovery over HDMI is complicated. The audio data's packetised and sent in bursts, in between video lines. It's up to the receiver to do a good job of clock recovery - in theory it could do it quite badly. But it could also do it perfectly.

I wouldn't say that HDMI is inherently inferior on that score. But in practice, HDMI seems to cause problems in all sorts of areas by being complicated. There's lots of scope for errors and incompatibilities.

48kHz vs 96kHz for HDMI would have nothing to do with jitter. It couldn't affect anything like that, at least for HDMI.

I repeat what I said elsewhere - if the data is 48kHz on disc, the player should by default be outputting it at 48kHz. It shouldn't be attempting to "improve" the data. In HDMI output mode, it should be functioning pretty much as a plain transport, like a DVD or CD player with S/PDIF.

Outputting at higher rates can cause problems - some receivers can't handle 96kHz signals as well as 48kHz signals (fewer processing options function).

Sigh! Just trying to get the point across that doubling the clock (sample) freq reduces the range that jitter can affect the final exact timing of the D/A conversion. It seems intuitively obvious to me as an engineer. Others seem to agree for the use of a 2x oversampling clock as a HDMI 1.1 jitter solution.

http://www.dtvforum.info/lofiversion...hp/t17222.html

The article you quoted goes into the poor jitter performance of AEU cables versus a coaxial S/PDIF connection and does not really address the over-sampling issue as much as the maximum frequency response of the cabling issue. Similar concerns have been raised for optical Toslink vs coax (high quality coax tends to do much better for sharper/(less jitter) clock edges (embedded in the datastream)). Whereas HDMI cable has to carry very high freqs (165 MHz) so it does fine for carrying a sharp (no ringing) clock edge embedded in the datastream.