Eye Diagram in new Microconverter HDMI-SDI 3G

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FranCaprGonz

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Eye Diagram in new Microconverter HDMI-SDI 3G

PostWed Oct 06, 2021 6:04 am

Hello,
Actually we are working with newer Microconverter HDMi To SDI 3G (P/N:CONVCMIC/HS03G/wPSU). We are experimenting a issue with jitter. The Eye diagram and UI is worst than older version without "3G" (P/N:CONVCMIC/HS/wPSU).

Its' possible to add a pre/post-enphasis to increment the ramp or make changes to improve it. We have various microconverters and all have the same output.

Eye Diagram version without 3G (P/N:CONVCMIC/HS/wPSU)
Image


Eye Diagram version with 3G (P/N:CONVCMIC/HS03G/wPSU)
Image


Franco Capraro
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FranCaprGonz

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Re: Eye Diagram in new Microconverter HDMI-SDI 3G

PostWed Oct 20, 2021 9:01 am

Anyone has the same problem ?? I dont get any answer from BlackMagic.
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Asgeir Hustad

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Re: Eye Diagram in new Microconverter HDMI-SDI 3G

PostSat Oct 23, 2021 4:58 pm

The eye doesn't look terrible, and you are running at twice the signal rate on the second image.

Is this actually causing you an issue in use? You're not saying what your issue is, just that "the raw signal looks worse". That shouldn't really matter if it passes your video..
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FranCaprGonz

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Re: Eye Diagram in new Microconverter HDMI-SDI 3G

PostMon Oct 25, 2021 5:48 am

Asgeir Hustad wrote:The eye doesn't look terrible, and you are running at twice the signal rate on the second image.

Is this actually causing you an issue in use? You're not saying what your issue is, just that "the raw signal looks worse". That shouldn't really matter if it passes your video..


The signal is the same for both cases. Phafrix is just assigning different Inputs. I will upload another images.

The standard SDI say:

"In order to be considered compliant with SMPTE 424M (the 3 Gbps SDI physical specification), a piece of equipment must have output jitter of no more than 0.3UI. The standard for HD-SDI is 0.2U"

So if im starting with a jitter of 0.25UI with just a 0.5M cable and really slow Eye Opening, when i use a cable of 5Meters will be really worst. That the issue

Having 2 board older than this "3G version" of the same brand (BlackMagic but older version) with really better results is something strange.
Last edited by FranCaprGonz on Tue Oct 26, 2021 9:03 am, edited 1 time in total.
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FranCaprGonz

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Re: Eye Diagram in new Microconverter HDMI-SDI 3G

PostMon Oct 25, 2021 6:05 am

Here another example. As you can see its almost 3 times worst. Im not saying is bad output, but you need to know that im using a 0.5M cable.

3G Converter
0.15UI
Eye Diagram more diffused
Image


Old Converter
0.06UI
Eye Diagram totally defined
Image
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Xtreemtec

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Re: Eye Diagram in new Microconverter HDMI-SDI 3G

PostTue Oct 26, 2021 8:40 am

Asgeir Hustad wrote:The eye doesn't look terrible, and you are running at twice the signal rate on the second image.


I have 6G screenshots that look cleaner than that :roll: For 3G that looks terrible!! Such a poor driver performance will reduce your cable length a LOT as receiver jitter is going trough the roof and not able to get a clean clock sample anymore.

Phabrix QX 12G  Generator to Analyser loop   6G SDI    2018-09-17T184643.png
Phabrix QX 12G Generator to Analyser loop 6G SDI 2018-09-17T184643.png (211.17 KiB) Viewed 504 times

6G SDI with 5 meter of cable :) Phabrix QX12G analyser

The old converters rely on Semtech chipset which is rather good in generating a clean SDI signal.
We ditched most new 3G converters and are buying into the old units were we can find them.. As they perform much better!! It's a shame BMD choose to go the FPGA way instead of the clean hardware conversion they had before.

They now use a rather Old ( 13 years old ) Texas Instruments sdi driver which seems to not perform as well as the Semtech chips. Looking at the datasheet of the TI chip it does not have as much tools as the newer chips to compensate for rise and fall times. Swinglevel etc. :cry:
Daniel Wittenaar .:: Xtreemtec Media Productions ::. -= www.xtreemtec.nl =-
4K OBV Trailer, ATEM TVS HD, 4M/E Broadcast Studio 4K, Constelation 8K, Hyperdeck Studio 12G, Ursa Broadcast 4K, 4K fiber converters with Sony Control
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FranCaprGonz

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Re: Eye Diagram in new Microconverter HDMI-SDI 3G

PostTue Oct 26, 2021 9:09 am

Xtreemtec wrote:I have 6G screenshots that look cleaner than that :roll: For 3G that looks terrible!! Such a poor driver performance will reduce your cable length a LOT as receiver jitter is going trough the roof and not able to get a clean clock sample anymore.


Thats exactly what i was trying to say. Im totally agree with you. You get a really good Eye Diagram :o

Xtreemtec wrote:The old converters rely on Semtech chipset which is rather good in generating a clean SDI signal.
We ditched most new 3G converters and are buying into the old units were we can find them.. As they perform much better!! It's a shame BMD choose to go the FPGA way instead of the clean hardware conversion they had before.

Yes, in my case i couldnt find old's HDMI to SDI Converters of BMD. ( We have just some of them to make tests.

Hope we get some answer from BMD.
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Dave Del Vecchio

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Re: Eye Diagram in new Microconverter HDMI-SDI 3G

PostTue Oct 26, 2021 9:40 pm

Xtreemtec wrote:The old converters rely on Semtech chipset which is rather good in generating a clean SDI signal.
We ditched most new 3G converters and are buying into the old units were we can find them.. As they perform much better!! It's a shame BMD choose to go the FPGA way instead of the clean hardware conversion they had before.

They now use a rather Old ( 13 years old ) Texas Instruments sdi driver which seems to not perform as well as the Semtech chips. Looking at the datasheet of the TI chip it does not have as much tools as the newer chips to compensate for rise and fall times. Swinglevel etc. :cry:
I assume the reason for usage of the FPGA in the MicroConverter 3G models is to support HDMI to SDI timecode conversion and to support 3D LUTs for color correction on the SDI to HDMI 3G model.

I don't believe that HDMI timecode is really an official part of the HDMI spec, so they may have needed the FPGA to correctly handle the timecode metadata. And for the LUT support, the converter is actually modifying the output video signal (which can be applied to the SDI loop out as well), rather than straight video pass-through.

It's a little less clear why they needed to change the SDI driver components used though.
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Xtreemtec

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Re: Eye Diagram in new Microconverter HDMI-SDI 3G

PostTue Oct 26, 2021 10:10 pm

Because they now only need a sdi EQ and a Sdi cable driver. Where the previous chip they used was a sdi receiver + reclocker to 10bit parallel data that got straight into a hdmi cable driver. ;)

Which is how almost all sdi > hdmi converters work. It is a proven concept and has the most optimized conversion based on latency and performance. Those converters where the only one that stayed cool and did not overheat nor could bake an egg on.

Yes I get the step we’re they went for a FPGA as it opens doors like LUT conversion etc. But the conversion is slower, a lot of users report problems with these devices not negotiating as well as the old ones with other hardware. And based on these eye diagrams the output drivers don’t look very promising.
Anyway I really admire what they done as they have been able to make a box with a pretty modern fpga inside that does sdi manipulation under 40 bucks which is quite amazing. Will need a few FW updates before it is running smooth for most users.

And based on my quick look at the datasheet of the output driver I don’t have high hopes they will be able to fix those output eyes very much. That output chip is very limited in what it can do in terms of optimalisation.

The more modern versions of these have all kinds of compensations that you can adjust.

Anyway at the moment with the current chip market situation. It’s better to have something then not be able to deliver your hardware product at all. We seized producing 2 products already due to this issue.
Daniel Wittenaar .:: Xtreemtec Media Productions ::. -= www.xtreemtec.nl =-
4K OBV Trailer, ATEM TVS HD, 4M/E Broadcast Studio 4K, Constelation 8K, Hyperdeck Studio 12G, Ursa Broadcast 4K, 4K fiber converters with Sony Control
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FranCaprGonz

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Re: Eye Diagram in new Microconverter HDMI-SDI 3G

PostWed Oct 27, 2021 5:29 am

Xtreemtec wrote:Because they now only need a sdi EQ and a Sdi cable driver. Where the previous chip they used was a sdi receiver + reclocker to 10bit parallel data that got straight into a hdmi cable driver. ;)

Which is how almost all sdi > hdmi converters work. It is a proven concept and has the most optimized conversion based on latency and performance. Those converters where the only one that stayed cool and did not overheat nor could bake an egg on.

Yes I get the step we’re they went for a FPGA as it opens doors like LUT conversion etc. But the conversion is slower, a lot of users report problems with these devices not negotiating as well as the old ones with other hardware. And based on these eye diagrams the output drivers don’t look very promising.

Anyway I really admire what they done as they have been able to make a box with a pretty modern fpga inside that does sdi manipulation under 40 bucks which is quite amazing. Will need a few FW updates before it is running smooth for most users.


Yes im working in a HDMI to SDI converter in FPGA based and it show a lot of problem in terms of Sync, but not in terms of Eye Diagram, so i understand your point.

Xtreemtec wrote:And based on my quick look at the datasheet of the output driver I don’t have high hopes they will be able to fix those output eyes very much. That output chip is very limited in what it can do in terms of optimalisation.

The more modern versions of these have all kinds of compensations that you can adjust.


Maybe if they add some Pre Emphasis in the signal, so they can obtain a better transition between "0" and "1", something like this:

Image

Xtreemtec wrote:Anyway at the moment with the current chip market situation. It’s better to have something then not be able to deliver your hardware product at all. We seized producing 2 products already due to this issue.


We have with similar issues, do you obtain some vendor with old versions of this converter (or the 6G converter) ? I think no because it was discontinued for almost 1 year.
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Xtreemtec

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Re: Eye Diagram in new Microconverter HDMI-SDI 3G

PostWed Oct 27, 2021 6:16 am

I keep my eye out for 2nd hand units. Bought a batch of 10 recently of a company that stopped with there video department. Yes they are used. But if you treat them well they will last a long time.
Daniel Wittenaar .:: Xtreemtec Media Productions ::. -= www.xtreemtec.nl =-
4K OBV Trailer, ATEM TVS HD, 4M/E Broadcast Studio 4K, Constelation 8K, Hyperdeck Studio 12G, Ursa Broadcast 4K, 4K fiber converters with Sony Control
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Dave Del Vecchio

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Re: Eye Diagram in new Microconverter HDMI-SDI 3G

PostWed Oct 27, 2021 7:42 am

FranCaprGonz wrote:We have with similar issues, do you obtain some vendor with old versions of this converter (or the 6G converter) ? I think no because it was discontinued for almost 1 year.
The HDMI to SDI 6G and SDI to HDMI 6G Mini Converters are still available new, it is only the original Micro Converters (without the 3G designation) that have been discontinued. The 6G converters are around 3 times the price of the 3G converters though.

But in terms of maximum cable length, I have typically had better results with the 6G converters than with the Micro Converters (even the original non-3G ones). For example, there are times where a 3G SDI (1080p50/60) video signal didn't work over a particular cable run with the Micro Converter, but did work after swapping it out for one of the 6G converters. I assume this was due to better performance of the 6G-capable SDI chipsets, as the video signal and cable were the same otherwise.

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