I've had a big downer on HDMI (and V1.3 in particular) for as long as I can remember. TrueHD & DTS-HD compatibility made me think twice, though, but something happened today that got me really hopeful for audiophile standard interfacing in the near future. Really not sure where to put this thread, as it's about HD audio quality. HiFi? Receivers? Audio processors? HD DVD? Blu-ray? Cables? Dunno, I guessed it was most appropriate here, going by the usual audience. Well, I was browsing the latest HDMI V1.3a specification today....
What?
What 's so funny?
Doesn't everyone?
Anyway, I stumbled across a small new section that I hadn't seen or heard of before. This described, in not very much detail, a new and optional facility for the audio clock in the processor / amplifier to control the clock in the source using a CEC Set Audio Rate command back the source. Here's what the spec says:



Quote:

7.11 Audio Rate Control Overview The Audio Rate Control feature allows a Sink to slightly and continuously adjust the audio clock rate of the Source in order to match the Sink’s crystal-based audio clock. The Sink controls the Source’s audio clock rate with the CEC <SET Rate Audio>command. See CEC Supplement section CEC 13.16 for details. Source ACR behavior is not affected by Audio Rate Control. When Audio Rate Control is enabled the Source shall continue to generate correct ACR packets that accurately reflect the current (possibly adjusted) audio clock rate.

So what does this mean for us? I'm not entirely sure, as the new capabilty doesn't look closely defined, but to me it reads very much like Sony and Pioneers' descriptions of iLink operation. That's a rate adaptive connection, where the sink (amp) has the master audio clock, rather than the other way round.

It's not a synchronous connection, but I think it's a good thing because the timing information doesn't have to come from the player. That means it's less susceptible to the jitter from (usually) a video clock, a less-than-stellar connection, and an audio clock regenerator in the amp that is slaved to the player. In this configuration, the timing information is generated in the amp, leaving the source to supply only the digital amplitude information. So bits really will be bits for once. Timing info is sent back to the source to maintain flow control.

I don't know where this came from, and I don't know why I never noticed it before. Maybe the audiophile manufacturers, so dismayed by the disappointing jitter performance of HDMI, have been lobbying HDMI for something better. If this is it, then I think we have a great deal to look forwards to. Note that this facility was not incorporated in HDMI V1.3, though, only 1.3A.
Well chuffed,

-----------------
Nick

On 2008-09-15 14:10, MNSACD wrote:
Well, thank you for all the info!  So my next question is, are the lower end ES servers like the 4400ES HDMI 1.3a compliant????  
Thanks again!
MNSACD

On 2008-09-16 04:39, Welwynnick wrote:

• Member Quote

That's not really the right question unfortunately.   There may be many amplifiers that are HDMI 1.3a "compliant" but this is not very meaningful.  All the incremental features of each HDMI version are optional, not compulsory, which almost completely undermines the value of the spec.

What HDMI say is that you have to look for the features that you are looking for in the manufacturers specification, and not depend on the HDMI version.  Where there are features like DSD, ARC, bitstreaming or whatever that are supported by a particular piece of kit, they will be clearly advertised by the manufacturer.  If they are aren't, then assume they aren't there.

The 6400ES has HATS, but other receivers like the 4400 almost certainly won't, even if they are HDMI 1.3 a "compliant" (note the mocking quotes).   ARC / HATS / PQLS makes a significant change to the internal architecture of both players and amps, and I expect it will be a feature of higher-end equipment.

Nick

On 2008-09-16 13:11, RWetmore wrote:
I doubt there will much much, if any, difference.

On 2008-09-17 05:10, Welwynnick wrote:

• Member Quote

I'm a bit conscious of swamping this thread, so I held back from replying.  I think ARC / HATS / PQLS / i-link are well worth  having, though I haven't been in the position of trying to equate the benefit to a budget.  I've simply owned and used a couple of players and amps that have i-link, and found it very worthwhile having.  I would expect the HDMI implementation to be very good as well.

As to whether its worth $1000 is more difficult, and depends on the value that the owner places on sound quality.  I doubt that the comparison is a simple as that though.  You are getting a better amplifier in many other ways for the extra $$$, and I doubt that HATS accounts for very much of that.

On the reasonable assumption that the 6400 is better than the 4400 anyway (and you might get some clues about that from it's weight and power consumption) I would say that the 6400 was worth the extra.  The effect of minimising jitter is just magic; its so difficult to go back knowing what you're missing.  

Rwetmore, can I just ask though, how do you conclude that there won't be much difference?  I've read you quite a lot but don't know your system - have you heard i-link?
regards,   Nick

[ This message was edited by: Welwynnick on 2008-09-17 05:12 ]

On 2008-09-17 05:10, Welwynnick wrote:
The effect of minimising jitter is just magic; its so difficult to go back knowing what you're missing.

On 2008-09-16 13:11, RWetmore wrote:
I doubt there will much much, if any, difference.