Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems 621, 121 and 421

Thanks Shawn
Great explanation of an obviously complex, but very important, potential issue

Yes, I know. But a lot of people think: "If it's digital, it either works perfect or not at all". With packet-based digital transmission, some think it's even more perfect since they believe there can be ACK/NACK and resending of packets.

From googling around it appears HDMI is bidirectional. What it's used for I'm not sure.

http://www.articlesbase.com/cable-and-satellite-tv-articles/is-hdmi-worth-the-cost-208429.html

My guess is that it's more for EDID Data of the Display and to make sure that HDCP is in play for Copy Protection reasons. No HDCP, then the Player / Source doesn't send the Data Stream (hence some of the issues with the Clux and EDID issues with some displays)

Seriously doubt that the Bidirectionality is anything to do with the Ack / Nack side of things but someone here might know better

I believe the bidirectionality of HDMI is for control, a poor-man's Meridian COMM's. A TV and a DVD recorder/VHS/DVD Player... from the same company can talk to each other by sending commans over HDMI - "Viera Link", "Bravia Theatre Synch"...

Meridian also uses HDMI like this as a comms option for the 421 linked to the G91.

Does anyone have any links to what kind of problems HDMI video is susceptible to? I've never heard or read anything about the picture being degraded or interfered with. Neither have I ever heard of jitter being a problem for the picture. My understanding and experience is that if you choose the proper gauge for the length of cable, and if your cable isn't broken, you should not be experiencing any picture problems. Is this correct? Before installing 35ft of cable into my system, I read lots of tests about Monoprice/Bluejeans cable vs MonsterCable high end HDMI. All the tests claim that Monster provides no advantage, and infer that a perfect picture is attainable via HDMI using inexpensive, properly built wire. How does Meridian's proprietary active termination, automatic cable equalisation, buffering and de-jittering technology visibly improve image quality, reduce noise and stabilise the video - even on short cable runs???

Do a google search for 'HDMI eye'. The HDMI signal should arrive as a clean 'eye' shape, but can degrade depending on distance or resolution/bandwidth. The technology that some companies, including M, clean up the signal and restore the eye shape.

Here is the official explanation: http://www.HDMI.org/installers/eyediagram.aspx

The important part is "signal attenuation and interference in an HDMI cable will increase over distance, until at a certain length the signal-to-noise ratio becomes unacceptable.". Basically, when SNR exceeds the ability of the receiver chip to decode the signal, the image will degrade - sparklies etc, until the image/audio finally becomes impossible to decode.

Various cable/repeater manufacturers have their own explanation and how their technologies improve the signal. But having the cleanest signal arriving at the receiver will give the best chance of the receiver correctly decoding the contents. However, if your signal is already relatively clean, then obviously this functionality will have no visible/audible effect.

I've read the eye stories before, and they are discussed in the Monster Cable HDMI shootout. They back up my understanding that there is no problem with the picture until a threshold is reached - too low a gauge for very long wire (35+ft) will not pass the most demanding signal and result in sparkles/dropouts. Beyond that there is no gradual picture deterioration or noise added. Monster's HDMI cable claims were effectively debunked.

http://gizmodo.com/gadgets/HDMI-cab...cable-+-grand-finale-part-iii-282725.php

How does Meridian's proprietary active termination, automatic cable equalisation, buffering and de-jittering technology visibly improve image quality, reduce noise and stabilise the video - even on short cable runs??? At its price, I'd buy a 121 if I am losing resolution over my very long cable run, which is probably 40-45ft if I include the cable after the switch.

I think that on short cable runs of good cable normally image quality differences are smaller than at source level. Differences in image quality on different Blu-ray/DVD's are far more noticable.

I believe this talk mostly comes from when people stepped up in resolution from 720p/1080i to 1080p. Cables made for 720p that worked perfectly now were low on bandwidth and you could get various problems and hih requency detail loss. With today's cables I think you are safe on shorter runs, and for longer runs a pretty simple signal amplification is enough.

Tommy,

Can you point me to a link about high frequency detail loss? All I can find are articles that indicate success or obvious, major problems - speckles or dropouts. Eg. If you are trying to pass a 1080p signal over a cable rated for 720p, you will unquestionably see problems. If you are trying to pass 1080p over a cable that actually is designed to pass 1080p, then you will only have problems if the cable is broken or too long. Where does the de-jittering, etc. come into play?

This is not true. All you know for certain is that 720p has been tested and passed whatever qualifications are mandatory for 720p. It may or may not work at 1080p, but there are no guarantees.


I wish that that were true. Sadly, it is not.



In the receiver, not in the cable. All a passive cable can do is not add to the problem.