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Problem getting 4K through hybrid optical cable + short passive extension cable

1705 Views 39 Replies 4 Participants Last post by  Otto Pylot, 
A
Hi,

I'm having the following problem. If I connect my Sony UBX-800Mk2 directly to my Epson EH-TW9400 with this cable:

Active HDMI optical fiber cable with slim connector - versie 2.0 (4K 60Hz HDR) - 15 meter / 50 ft
connectors: HDMI-A (male) - Micro HDMI-D (male)
includes adapter HDMI-A (male) - Micro HDMI-D (female)
HDMI 2.0 specifications (Premium High Speed HDMI)
Suitable for 3840 x 2160 @ 60 Hz
HDR (High Dynamic Range) support
Active hybrid optical fiber cable (AOC)
Click to expand...
I get a 4K signal through. However, if I insert this short (6 ft) passive extension cable between the bluray player and the optical cable

Flat HDMI extension cable - version 2.0 (4K 60Hz HDR) / black - 1,8 meter / 6 ft
OKS-93289
connectors: HDMI-A (male) - HDMI-A (female)
HDMI 2.0 specifications (Premium High Speed HDMI)
Suitable for 3840 x 2160 @ 60 Hz
HDR (High Dynamic Range) support
Click to expand...
I don't get a 4K signal through, it's all black; the projector does not say No Signal. A regular 1080p signal still comes through just fine.

What could be the cause and, more importantly, what would be the solution?

Over at htforum.nl someone mentioned that the description of the short passive extension cable mentions that the total length of that cable + the original cable should not exceed 5 meters but surely that applies to the case where both cables are plain old passive cables, right?

If I understand correctly this type of hybric optical cable only converts the TMDS display data channels to optical and some or all of the other data channels are passed through directly through copper. Could that be the problem??? Compared to the TMDS those other channels are relatively low speed and I don't think the bandwidth they use increases with higher display resolution/bit depth, or does it? Since 1080p works fine with both cables connected I find it hard to believe that the non-TMDS channels could be the problem here (if my assumption is correct about the bandwidth of those non-TMDS channels being constant).

There is of course the single added connector transition but that's why I opted for an extension cable with a female connect at one end rather than a regular HDMI cable with two male connectors.

I need to make this work somehow because replacing the optical cable is going to be extremely difficult or even impossible. It runs in flexible PVC conduit but the cable was pulled through the conduit before the conduit was installed and it makes a few corners (not too sharp) that the rather long connector might not be able to make. And the cable itself is working fine at 4K, just not in combination with the short extension cable.

I cannot imagine that the optical fiber has broken, in that case I would rather expect nothing to get through but like I said 1080p works fine.

I suppose I could insert a repeater between the short extension cable and the optical cable but I would think that the circuitry at the source end of the optical cable acts as a repeater itself for the copper wire pairs in which case that would be pretty pointless. Also, I'm not sure if the optical cable would still get any or enough power from the HDMI output if there's a repeater or something in between which also takes power from the HDMI output.

I also cannot imagine that the short extension cable is somehow causing insufficient power to be available to the optical cable, or could that be it? I have no idea of the wire gauge in that flat cable, I only selected it because it was the one I could get the quickest; I would have preferred a regular round exension cable.

I am going to insert a 4x2 HDMI switch between the source and the short extension cable. Would that make any difference?

Any ideas?
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T
The overall length will matter but it's complicating things when you're using an active cable and any kind of extension cable. You're adding signal degradation. I've added pigtails to mine and they still work but the more cable the weaker the signals going to get. The active cable length typically doesn't matter if it's fiber. But then you're adding more cable to the end of it so the signals good enough with just the active cable but then your degrading it too much adding more cable. More than likely the transceiver in the end of the cable has just enough power to get a signal to you a directly connected device, it's not expecting to have a strong enough signal to continue through another cable.

You may get lucky and find a higher quality cable that you can add to it or possibly an extender/repeater box of some kind. As you suggest, a switch could help. In my mind a switch should take the signal and then power and repeat the signal through another port or cable. If it's not doing that you may still be out of luck.

That's frustrating that you went through the trouble of adding conduit and it's not helped out when you needed it. Certain folks here I think it's the magical solution to everything even cables that don't work as advertised.
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Ratman
Tanquen said:
That's frustrating that you went through the trouble of adding conduit and it's not helped out when you needed it. Certain folks here I think it's the magical solution to everything even cables that don't work as advertised.
Click to expand...
As explained many times.... conduit doesn't create a magical solution for picture/audio quality. It is suggested to facilitate cable changes/additions/removals if or when necessary.
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Otto Pylot
Active cables should not be pig tailed with other cables. Most, if not all active cable mfrs recommend not using passive extensions with active cables. An active extension may work but 4k HDR connections should really be as simple as is possible. That is, source to sink, with nothing in-between.

50' is certainly doable but active hybrid fiber cables do have copper wiring for low bandwidth requirements (ARC, EDID, HDCP) and with cheaper made cables or non-quality components that COULD be a cause of issues.

A properly installed conduit with a pull string does nothing to the cable other than make it a lot easier, and safer, to install/update the cable if need be. For long runs installed in-wall it is really the only way to future proof. And by future proofing we mean cable installation.
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Ratman said:
As explained many times.... conduit doesn't create a magical solution for picture/audio quality. It is suggested to facilitate cable changes/additions/removals if or when necessary.
Click to expand...
No one said anything about picture quality. And many many many many times it's used as an excuse for a particular manufacturer that had cables that weren't working as labeled and/or failing after a time. It's no big deal just make sure you have conduit.

It is a big deal, it is a pain in the butt. I don't want to buy more cables and rerun cable when I don't have to, ever. I don't care if I have conduit or not. Make a thread that extols the virtues of conduit and the best ways to do it. Don't tell people it's no big deal that the cable may not work as labeled when you try to use a feature later on or fails in 2 month because you have conduit right. It's no big deal to just get whatever cable works at the moment instead of looking for one that may work for future hardware because you have a conduit right? It's no big deal.

Cables that last 10 years are a fairy tale, that is completely not true. I've said a couple of times that I had an HDMI cable that lasted about 10 years and the only reason I switched it is because I wanted 120 hertz for gaming. And still I keep hearing that it's a fairy tale and you can't have a cable that lasts that long and so on and so forth. Just now I explained that I'm using an active cable with pigtails (my factual honest personal experience) and it works just fine and then we hear that active cables should not be pigtailed with other cables whatever that means. Who cares, it can work is what's important as I already said having more cables can degrade the signal and make it harder, regardless of length and type of cable.

Some of us can't run conduit or would be too costly to run conduit or like the unfortunate OP, they ran conduit but it's still a nightmare. Some might think that points to an advantage of getting a cable that actually does as advertised and works for the future because regardless, for some folks rerunning a long cable is going to be a pain. You've got other cables in the conduit already or the conduit was run poorly or whatever. That doesn't excuse cables that don't work as advertised. That doesn't mean people shouldn't look for a cable that's going to last as long as possible.

The fact that it has a chance to make things easier in the future is great but completely irrelevant from the numerous posts people have made tying it to why it's okay to use a certain cable and not worry about getting a cable that actually works as labeled and that may work when you upgrade hardware later on or trying to find a cable that you hope will last you 10 years.
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First of all thank you all very much for taking the time to reply.

Maybe this wasn't clear enough from my original post, but the short passive extension cable comes before the optical cable, not after:

Sony bluray ----> 6 ft passive extension cable ----> active optical cable ----> Epson beamer

For the TMDS signals, signal level at least should not be an issue as they get converted to optical inside the 'source' connector of the optical cable. I'm sure that is done digitally, ie. if the electrical signal is decoded as a '1' it gets converted to an optical '1' at 'full level' and vice versa.

What I don't know is if the TMDS signals get re-clocked by the circuitry in the optical cable.

What I also don't know is if the non-TMDS signals get essentially decoded and repeated or 'amplified' or if those are just passed along passively.

Apart from that last bit, I would think that as long as the optical cable's source end connector (second ---->) circuitry gets a good HDMI signal (and with only 6ft of cable between the bluray and that connector it ought to), the circuitry inside that connector should be able to decode the signal and re-transmit it optically without any problem.

Again, the non-TMDS signals that travel through copper even in the optical cable would be susceptible to signal degradation but if those non-TMDS signals use the same bandwidth for 1080p as for 4K that would mean that since 1080p works for those signals, 4K should work too.

I ran conduit just so that hopefully I would be able to replace cables if needed, it's not going to improve signal quality in any way obviously. I did also run a CAT7 wire through that same (1") conduit (as well as a toslink cable) so if all else fails I could perhaps use the CAT7 wire with a pair of HDMI over CAT extender boxes instead of the optical HDMI cable. But first I want to see if I can get the HDMI cable to work.

I guess I will have to wait until I receive my HDMI switch (the one I want is sold out at the moment), although I may also get another short HDMI extension cable (maybe one that's 'rated' for 8K) to see if that makes any difference. Or I could try using a pigtail with a normal HDMI cable but that actually adds a connection so in principle it should be worse than a cable with a female connector at one end.

Any further thoughts?
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ArjanPSD said:
First of all thank you all very much for taking the time to reply.

Maybe this wasn't clear enough from my original post, but the short passive extension cable comes before the optical cable, not after:

Sony bluray ----> 6 ft passive extension cable ----> active optical cable ----> Epson beamer

For the TMDS signals, signal level at least should not be an issue as they get converted to optical inside the 'source' connector of the optical cable. I'm sure that is done digitally, ie. if the electrical signals is decoded as a '1' it gets converted to an optical '1' at 'full level' and vice versa.

What I don't know is if the TMDS signals get re-clocked by the circuitry in the optical cable.

What I also don't know is if the non-TMDS signals get essentially decoded and repeated or 'amplified' or if those are just passed along passively.

Apart from that last bit, I would think that as long as the optical cable's source end connector (second ---->) circuitry gets a good HDMI signal (and with only 6ft of cable between the bluray and that connector it ought to), the circuitry inside that connector should be able to decode the signal and re-transmit it optically without any problem.

Again, the non-TMDS signals that travel through copper even in the optical cable would be susceptible to signal degradation but if those non-TMDS signals use the same bandwidth for 1080p as for 4K that would mean that since 1080p works for those signals, 4K should work too.

I ran conduit just so that hopefully I would be able to replace cables if needed, it's not going to improve signal quality in any way obviously. I did also run a CAT7 wire through that same (1") conduit (as well as a toslink cable) so if all else fails I could perhaps use the CAT7 wire with a pair of HDMI over CAT extender boxes instead of the optical HDMI cable. But first I want to see if I can get the HDMI cable to work.

I guess I will have to wait until I receive my HDMI switch (the one I want is sold out at the moment), although I may also get another short HDMI extension cable (maybe one that's 'rated' for 8K) to see if that makes any difference. Or I could try using a pigtail with a normal HDMI cable but that actually adds a connection so in principle it should be worse than a cable with a female connector at one end.

Any further thoughts?
Click to expand...
That could be more of an issue but I still think its down to the extra length or maybe quality. Wiring wise there should be no difference from connecting directly to the port or putting a pigtail or 90° adapter in but you are degrading the signal with extension cable before it gets to the transceiver and maybe effecting the power draw it can receive. The signal may be clean enough for 1080 but not 4k or other features that increase bandwidth. It may just be the extension cable, do have any others you can try? Would need a simple coupler. Otherwise maybe the HDMI switch will do the trick, its hard to say.

I just use the pigtail for strain relief. So it's like a 6" extension cable but it works. I did have to get new ones as some older ones would not work with the 4k-120Hz. So it's not just length that can add to the signal loss.
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Ratman
Tanquen said:
It is a big deal, it is a pain in the butt. I don't want to buy more cables and rerun cable when I don't have to, ever. I don't care if I have conduit or not.
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Exactly! No one wants to (re)run cable(s) after an installation, no matter the reason. So try to stop with the "conduit" barbs please. That's not contributory to an HDMI problem/issue. Thanks!
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Here's my personal best theory so far: at 4K the electrical->optical circuitry at the source end of the optical cable is going to draw more power (amps) from pin 18. If that flat cables uses a very thin gauge conductor, the increased voltage drop (i² x r) might be just enough to keep the circuit from doing it's job properly. If that is true a different passive extension cable with a thicker gauge conductor for at least pin 19 might work.

Unfortunately I have no idea of the gauge of that conductor in this extension cable or in regular high quality HDMI cables so I don't know how likely an explanation this is.
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Otto Pylot
ArjanPSD said:
Here's my personal best theory so far: at 4K the electrical->optical circuitry at the source end of the optical cable is going to draw more power (amps) from pin 18. If that flat cables uses a very thin gauge conductor, the increased voltage drop (i² x r) might be just enough to keep the circuit from doing it's job properly. If that is true a different passive extension cable with a thicker gauge conductor for at least pin 19 might work.

Unfortunately I have no idea of the gauge of that conductor in this extension cable or in regular high quality HDMI cables so I don't know how likely an explanation this is.
Click to expand...
The potential issue is pig-tailing the passive cable to the active cable. The active cable needs a source of power for the chipset. The HDMI ports are standardized around 5v/50mA so the active cables are designed to utilize that 50mA current output for their chipsets. There is nothing for the active cable to draw from when physically connected to a 6' passive cable. The power draw for an active cable, in addition to other functions, is for error correction, timing, etc so a reliable, constant 50mA (at least) current draw is necessary for that to take place reliably. TMDS is a low power consumer but requires 3 twisted TMDS pairs for video transmission in HDMI and that physical design may be different with passive vs active cables because of what the chipsets in the connector ends of active cables do. The 8 copper wires in hybrid fiber cables are used instead of the traditional pin 13-19 wires of passive copper only cables. Additionally, if you are connecting a passive HDMI cable designed with the HDMI 2.0 option sets in mind to an active cable designed with the HDMI 2.1 option sets in mind there are going to be physical differences in design based, in part, on the more rigorous specs for HDMI 2.1 vs HDMI 2.0.

Afterthought: HDMI, while standardized to a certain degree it is still fraught with issues and quite often just doesn't make sense, especially when it comes to connectivity when using different products (cables, devices, etc). All you can do is try. You may get lucky. HDMI is not my favorite technology.
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Otto Pylot said:
The potential issue is pig-tailing the passive cable to the active cable. The active cable needs a source of power for the chipset. The HDMI ports are standardized around 5v/50mA so the active cables are designed to utilize that 50mA current output for their chipsets. There is nothing for the active cable to draw from when physically connected to a 6' passive cable.
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This seems wrong as the OP and I have both done that.
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Ratman said:
Exactly! No one wants to (re)run cable(s) after an installation, no matter the reason. So try to stop with the "conduit" barbs please. That's not contributory to an HDMI problem/issue. Thanks!
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pot meet kettle
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ArjanPSD said:
Here's my personal best theory so far: at 4K the electrical->optical circuitry at the source end of the optical cable is going to draw more power (amps) from pin 18. If that flat cables uses a very thin gauge conductor, the increased voltage drop (i² x r) might be just enough to keep the circuit from doing it's job properly. If that is true a different passive extension cable with a thicker gauge conductor for at least pin 19 might work.

Unfortunately I have no idea of the gauge of that conductor in this extension cable or in regular high quality HDMI cables so I don't know how likely an explanation this is.
Click to expand...
If you have a volt meter you may be able to get the pin out and see if the voltage and amps are there on the extension cable. I don't see why not but like I said I have a pair of 6" pigtails that don't work and another that do. I don't how HDMI power devices can work if the HDMI cable wont pass the power.

Maybe something like this:
Parts Express HDMI Cable Signal Tester
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Otto Pylot
Tanquen said:
This seems wrong as the OP and I have both done that.
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With a 6' passive cable, not a 90º elbow connector? 6" (that's inches) may work but 6' (that's feet) probably won't. So, you have a pair of 6 inch pigtails that work and some that don't? Interesting.

"I don't how HDMI power devices can work if the HDMI cable wont pass the power." Obviously.
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Otto Pylot said:
With a 6' passive cable, not a 90º elbow connector? 6" (that's inches) may work but 6' (that's feet) probably won't. So, you have a pair of 6 inch pigtails that work and some that don't? Interesting.

"I don't how HDMI power devices can work if the HDMI cable wont pass the power." Obviously.
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"There is nothing for the active cable to draw from when physically connected to a 6' passive cable."

You're the one that just said it can't work. Obviously. Yeah 6' or 6", I have one that works with 6-in pigtail and he has one that works with a 6-ft extension but not for 4K. How does that translate into, there's no way to get any power connected to a 6-ft passive cable?
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Otto Pylot
Huh? The active cable needs a power source for the chipsets to work. There is no "power" from a passive connector, just a data transfer. And yeah, HD (1080) works, but is a completely different protocol set/demands from 4k HDR.
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Otto Pylot said:
Huh? The active cable needs a power source for the chipsets to work. There is no "power" from a passive connector, just a data transfer. And yeah, HD (1080) works, but is a completely different protocol set/demands from 4k HDR.
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Huh indeed. He said his is working with 1080p and that's still using the passive extension cable and then the active cable. Even though it's only working at 1080p it still needs power to run the transceiver. Why should a passive cable not pass the power from the port? Just like my media device on the back of the TV has a little pigtail in case you can't fit it into the HDMI port in the back of the TV It's still passing power. Who's deciding when the cable or 90° adapter or pigtail or 1-ft extension cable or 6-ft extension cable stops passing power? It's detecting enough resistance and it's turning off power at the port?
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Otto Pylot
Tanquen said:
Huh indeed. He said his is working with 1080p and that's still using the passive extension cable and then the active cable. Even though it's only working at 1080p it still needs power to run the transceiver. Why should a passive cable not pass the power from the port? Just like my media device on the back of the TV has a little pigtail in case you can't fit it into the HDMI port in the back of the TV It's still passing power. Who's deciding when the cable or 90° adapter or pigtail or 1-ft extension cable or 6-ft extension cable stops passing power? It's detecting enough resistance and it's turning off power at the port?
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Never mind. HD (1080) transmission requirements are very different from 4k HDR. And when you add in the active cable part, and try to push 4k HDR with a passive cable to an active cable, issues will arise. But you seem to have a much better grasp of HDMI in general than I do so I'll leave it to you to accurately advise the OP.
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A
The passive 6ft extension cable clearly passes the 5V power supply from pin 19, otherwise the active optical cable would not work at any resolution. The only reason it's called an extension cable is because of the female connector at one end, other than that it should be exactly the same as any regular HDMI cable. And it's called passive because it's just a bunch of copper conductors without any active circuitry.

As for testing, yeah I have a voltmeter, I also have an oscilloscope (I have a MSc degree in ee), even though it doesn't have sufficient bandwidth to measure the TDMS signals at 4K, but for once I'd like to be just a consumer :). In any case just measuring the voltage on pin 19 without a load is not going to do any good and measuring in-circuit (with the cables and the load connected) would require splicing a cable which by itself would probably ensure that no 4K signal will get through. The kind of tester that does 4K appears to be pretty expensive also.

It would be nice if the Epson had a built-in HDMI diagnostics option in some service menu.

For now I have ordered a (hopefully) higher quality passive extension cable to use between the Sony and the optical cable, also in different lengths (1, 1.5 and 2 meters).

If that doesn't work I'm going to try a repeater, one that is USB powered and not just HDMI bus powered. I found several of those:

www.siig.com

HDMI 4K HDR Repeater

Provides a quick and convenient solution for extending HDMI cable transmission distance beyond normal boundaries
www.siig.com www.siig.com

Seems that neither of these do [email protected]@4:4:[email protected] bits but maybe that's not even possible with HDMI 2.0's available bandwidth? Heck, I'm not even sure what my projector supports exactly. Like I said, I want to be a consumer for once and just enjoy watching movies on my new projector (I used to have an old Barco Data 801s CRT projector until recently which I used for over 20 years). But I do want to get the 4K working since I do have a 4k-ish projector.

Any recommendations for a good 'usb powered' repeater?

I suppose I could also first try a voltage inserter, although what I should really do is wait until I get my matrix switch to see if that helps first.
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Otto Pylot
ArjanPSD said:
The passive 6ft extension cable clearly passes the 5V power supply from pin 19, otherwise the active optical cable would not work at any resolution. The only reason it's called an extension cable is because of the female connector at one end, other than that it should be exactly the same as any regular HDMI cable. And it's called passive because it's just a bunch of copper conductors without any active circuitry.

As for testing, yeah I have a voltmeter, I also have an oscilloscope (I have a MSc degree in ee), even though it doesn't have sufficient bandwidth to measure the TDMS signals at 4K, but for once I'd like to be just a consumer :). In any case just measuring the voltage on pin 19 without a load is not going to do any good and measuring in-circuit (with the cables and the load connected) would require splicing a cable which by itself would probably ensure that no 4K signal will get through. The kind of tester that does 4K appears to be pretty expensive also.

It would be nice if the Epson had a built-in HDMI diagnostics option in some service menu.

For now I have ordered a (hopefully) higher quality passive extension cable to use between the Sony and the optical cable, also in different lengths (1, 1.5 and 2 meters).

If that doesn't work I'm going to try a repeater, one that is USB powered and not just HDMI bus powered. I found several of those:

www.siig.com

HDMI 4K HDR Repeater

Provides a quick and convenient solution for extending HDMI cable transmission distance beyond normal boundaries
www.siig.com www.siig.com

Seems that neither of these do [email protected]@4:4:[email protected] bits but maybe that's not even possible with HDMI 2.0's available bandwidth? Heck, I'm not even sure what my projector supports exactly. Like I said, I want to be a consumer for once and just enjoy watching movies on my new projector (I used to have an old Barco Data 801s CRT projector until recently which I used for over 20 years). But I do want to get the 4K working since I do have a 4k-ish projector.

Any recommendations for a good 'usb powered' repeater?

I suppose I could also first try a voltage inserter, although what I should really do is wait until I get my matrix switch to see if that helps first.
Click to expand...
Do let us know how it all works out and what your final solution is. A voltage inserter is an interesting option for your situation but I'm not sure if that would work unless you inserted it between the passive cable and the active cable, or tired various combinations from either end (source or sink).

Some PJ's, for some unexplained reason, seem to have issues with hybrid fiber cables at long distances. That's one of the reasons that some cable mfrs include voltage inserters to be used between the active cable and the pj HDMI port. The thought is that some pj's have output current that fluctuates too much for the active cable so the inserter supplies 5V/500mA output instead of the usual 5V/50mA output. That has corrected the problem for some but nothing is definitive. That's not exactly your case but it might be worth a shot. VI's are inexpensive.
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