Minimum HDMI Cable Length (4 ft?)

The 50' for high speed can be problematic. Do you have Deep Color off? If you don't that could solve your problems (maybe). If Deep Color is already disabled, then yes a Cat 6 solution should provide an improvement in signal integrity.

The 1' versus 4' question is outside of my knowledge. Sorry.

I've never heard of a minimum length before and that advice from Monoprice sounds questionable. I have several 1.5' HDMI cables in use and have no issues with them.

Basically, what they are "quoting" is the need to have "some minimum length" of cabling that is likely related to the "need" for a "standard transmission interface" that has some form of "line build out" in its design. That "buildout" has minimums that it expects to "see" when looking out at the cable.... basically it provides a "matching" for impedances to provide "optimum" transmission to prevent "overly hot" OR highly reflection conditions.

No I didn't say that. In "real world transmission communication standards" (ie. strict telecommunications applications), design spec's are "well-defined" for a given interface (eg. long haul transmission, short haul, etc). Every manufacturer that expects his equipment to be used in the network publishes them AND follows them. In alot of cases, their interfaces are "switchable" in terms of the "line build out" because no one "fixed design" will meet the optimum conditions. Of course, they could do a similar thing in the HDMI world BUT the need and expense would not warrant it since "most applications" could/would probably fall between X and Y feet where X is some "small" number and Y is some large number. The large number is probably in that 30-35 foot range while the small number ... well... take your guess ... 1 foot, 2 foot, 3 foot ???? The problem is that most equipment makers don't publish their spec and thus the "best guess" of what their design is... is what I think they are quoting.... BUT there is a design spec (in the manufacturer's domain either internally and / or external) but I don't believe it is a "gold standard" like the equipment telecom industry standards. These are JUST consumer pieces where no one really cares if it works exactly as designed... just as long as it kind of works.... :-)

I work in the industry and there is no minimum length. If HDMI used pre-emphasis on its transmitters then possibly you might have a minimum length to knock down some of the pre-emphasized signal before it reaches an input. But pre-emphasis is not allowed for HDMI.

I can test HDMI signals direct from the output ports of a source device and there are no issues with the signal though it does not go through some minimum length of HDMI cable. The large, 50Ω single-ended cables I use to run to the oscilloscope match the impedance of the source traces and the loading at the oscilloscope so reflections are not an issue. I also use 1.5ft HDMI cables at work all the time to connect signal break-out boards together and they work fine.

I have to say that running 50ft of HDMI cable without an equalizer (booster) at the end is a little scary. I would try an equalizer before going with CAT5/6.

Haven't seen a need for a Minimum
Output cable length on the units we work with (we have 0.5m cables throughout various test rigs) - though I guess if your supplier says the kit they supply requires it your best to follow the advice.

A powered HDMI Extender up at the Projector is another option for you to consider.

Very few BD Discs are encoded in Deep Color and likewise only a few games - switch on Deep Color with 99% of BD Discs and your seeing the wrong colours!

Joe

I only use Vanco Installer series HDMI. I've never ran into problems up to 100ft.

http://www.amazon.com/Vanco-277050X-...3220064&sr=1-2

I use the 35ft and the 50ft all the time with projectors. Never a problem other than the occasional(2-3 per year out of hundreds) bad cable.

Another mis labelled cable - no way is it High Speed certified at 15m!

Like you lots of installs running perfectly well on Standard HDMI cables at 15m - even with 1080p, doesn't mean we don't also run 2 x CAT6 just in case though

Joe

0, since Blu-ray only supports 8-bit color. Even Deep Color test content is hard to find.

I'f I'd said no BD is Deep Color enabled someone would have found some obscure test disc that was

Hopefully the OP gets the idea!

Joe

to answer OP's orig question about min cable length, yes, a min length can be derived from the known tranceiver specs along with the characteristics of the cable being used. i dunno what min length for hdmi 1.3 is. just like ethernet the transceivers are sensitive to Fex and Nex (far and near end cross talk). too short of cable will take Fex and Nex to a level the transceiver cant handle thus creating errors. and keep in mind, not all transceivers are built well, etc.

4ft min is a good suggestion for 10Gb via twisted pair copper, but it all depends on cable design and the transceivers involved.

As I stated above there is no minimum length for HDMI cables. Denon_Kid, there are large differences between 10G Ethernet and HDMI. HDMI is a single direction signal (speaking of the high-speed TMDS signals) so transceivers are not involved. There are HDMI transmitters and HDMI receivers. Because of this, far end cross-talk and near end cross-talk is not an issue with HDMI. All TMDS signal travel from source to sink and experience similar attenuation. HDMI connectors have well controlled impedance through them so reflections are minimal and the TMDS pairs are supposed to be individually shielded so crosstalk within the cable is minute. FYI

nex and fex is not defined only by the transmitter/receiver pair, its a inherent issue that depends on cable length, construction type, frequency, etc etc. when you say "single direction signal" doesnt the 1.4a spec allow for bi-directional digital data flow, so doesnt this mean a 1.4a hdmi port is a transceiver, or does the return audio portion gets transmitted/received by some other device that is wired into the hdmi port??? 1.4a is not a "single direction" signal in the cable, and tmds is a form of lvds which means you have current flows in both directions with the differential cml on the receiver side (current loop).

i am not 100% up on the signaling. i suspect hdmi is parallel tmds to achieve the ~10Gb rate?

I have tested many HDMI cables, transmitters, and receivers over the last few years and never been able to see any crosstalk whatsoever on the TMDS signal lines. The shielding and connector design of HDMI mitigates this issue. I have seen crosstalk between the SDA and SCL wires of the DDC link on poor quality HDMI cables that twist the SDA and SCL wires together (dumb, dumb, dumb). Note that these wires are not shielded. I have tried to convince a specific Chinese cable manufacturers not to twist these wires together but they believe they must. Well... at least until they experience customer issues with HDCP signals unable to properly handshake on their longer cables!

HDMI 1.4a allows for a low data-rate audio return channel (ARC) to travel to on a wire pair in the cable, and I do believe that they use a separate IC for receiving the ARC signal. I have never heard anyone in the industry use the term transceiver related to HDMI. The data rate of the audio return channel approximately 1000x lower in data rate than the TMDS signals. Also TMDS signals are NOT a form of LVDS. They are a form of CML signaling. The design and specifications of LVDS Tx and Rx devices is very different than that of CML devices. If you would like to learn more about HDMI please check out the DVI specs from which HDMI was based:
http:/www.ddwg.org/lib/dvi_10.pdf

Transition Minimized Differential Signaling (TMDS) is 4 differential pairs of approx. 1Vp-p amplitude. They are DC coupled from open-collector sources to 50Ω pull-ups attached to 3.3V on the receiver. Three of the pairs are for DATA and one is a CLOCK signal (D0, D1, D2, CLK). A couple of data rates are 1.485Gbps each channel for 1080p @ 60Hz standard color (24bit) and 2.23Gbps for 1080p @ 60Hz with deep color (36bit).

Note that the Display Data Channel (DDC) signals on an HMDI cable are bi-directional making use of an I2C interface. Note that this type of communication only has one side talking at a time. The HDCP signals travel via DDC. As noted above I have seen crosstalk between the SDA and SCL wires which is due to coupling between the wires in a cable with these wires twisted together. Note that this type of crosstalk gets worse as the cable gets longer, so the shorter the better.

Cheers

That might explain some of the problems folks around here have had with longer cables...

fiberdude,
so after reviewing some of the cml used for tmds it would seem that there should be no minimum length limitation.

thnx for the info.

FWIW I think the source of this myth was problems monoprice was having with folks using short cables with one or more of their switches/splitters that included equalization.

Sorry to ressurect an old thread, but I was wondering if you could provide more info on this statement. I am having issues with a monoprice extender that only displays a blank screen when using my bluray player, but works with all of my other devices. Monoprice tech support is suggesting using longer HDMI cables to correct my problem. It doesn't seem like it would be causing my issue

Thanks,
Matt

How long is the cable from the switch to the display? Which extender?

I am using a 3ft monoprice 24awg high speed cable between the bluray player and the receiver and another 3 footer between the receiver and the extender(monoprice pid 8123). And a 6ft 24awg cable on the tv end of the extender.

Thanks,
Matt

I suspect others are wondering this as well, why do you need an extender for a 6-foot run?

Beat me to it. I just use 6' certified High Speed cables between my devices and a 3' cable from the BD player to the AVR.

Sorry if I was unclear here is my setup:

Bluray > 3ft hdmi > onkyo 709 > 3ft hdmi > monoprice 8123 extender > 67ft cat6 run > monoprice 8123 extender > 6ft hdmi > samsung pn59d7000

I have 3 other sources connected to the onkyo's inputs (xbox 360, directv dvr and an Acer aspire revo running XBMC) connected by the same model 3ft hdmi cables and they work perfectly at 1080p. I tried swapping out the cables to see if I had a bad cable possibly, but still no change. It seems odd to me that that all of the other devices work properly with 3ft cables but for some reason I need >4ft cables for the blu ray player.

Thanks,
Matt

Some more questions...Does the Onkyo 709 output sound from the Blu-Ray player with the 3ft cable while the display is showing the problem? Did changing from a 3ft cable to longer one solve the problem? Can't argue with success but it just seems more likely to be an Onkyo incompatibility with the Monoprice box. However, if the longer cable worked...