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BMD HDlink Pro - major problem

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Author Steve
Scene
#16 | Posted: 14 Jun 2012 07:11 
The box distorts any LUT applied to it, so I can't see how it can used under any circumstances in its present form. We are still waiting for a response from BMD on a fix. Until then the box is viewed by as as not being fit for purpose.

And yes, that includes Pomfort Live Grade.

Author Gabriele Turchi
Mono
#17 | Posted: 17 Jul 2012 23:45 
Steve

Hi Steve

good to know ( since i always used the HDlink Pro )
still no news ?

--is the issue on every HDlink model ( i have the PRO display port (that i use only to apply the Lut trough SDI passthrough )

--does the HDlink affect the brightness as well ? i have set my plasma to 110cdmq (with no lut ) than after the Lut i have checked and the brightness was 100 cdmq ...

i guess i will try to run the Lut using Resolve ...

thanks

g

Author Steve
Scene
#18 | Posted: 18 Jul 2012 12:15 
No news from BlackMagic at all... and I have chased them a lot. They know of the problem, but no fix yet.

The person to contact at BMD is (kristianl at blackmagic-design.com)

Please all feel free to mail him directly!



The problem is LUT accuracy, not brightness, but if the RGB levels are changed that will alter brightness too.
I have seen the problem on all versions of HDlink Pro.

Steve

Author Gabriele Turchi
Mono
#19 | Posted: 18 Jul 2012 14:21 


i was thinking : i use the HDlink looping the SDI while applying the Lut ,

you sad that the the HDLink distort the signal even without the Lut (which is not good ) but do you think that is be only issue or it will badly read and translate the lut as well ?

i mean : if when i read the patches in LS i use the HDlink SDI loop , shouldn't that "distorted" signal be ""considered "" by lighspace ?

thanks

g

Author Steve
Scene
#20 | Posted: 18 Jul 2012 14:38 
The main problem is with the box distorting the LUT incorrectly...
This depends on the LUT data, so LightSpace can't counter for the distortion. It changes depending on the LUT.

Basically, we no longer use HDlink Pro boxes for ANY LUT work.

Author Gabriele Turchi
Mono
#21 | Posted: 18 Jul 2012 14:39 
ok , in that case is bad ...

i will try loading the lut in Resolve ...

thanks
g

Author Peter Sartwell
Mono
#22 | Posted: 25 Jul 2012 23:29 | Edited by: Peter Sartwell 
Perhaps I'm seeing similar behavior, but even without a LUT applied.

Back in May 2010, I observed some black clipping in our 3 HDLink Pros, with gain set to unity. Generating SMPTE HD 219 bars from both Avid DS and Sony SRW-5800 in dual-link 444 RGB, the 11.5IRE bar in the pluge pattern wouldn't display. It showed only the right-most, higher IRE bar, and reproduced the 2 left bars as a single block. This was observed on a variety of displays regardless of settings, including 2 HP Dreamcolors. The Dreamcolors allow lots of level control, but no amount of black level or brightness adjustment showed the 3 discrete bars.

By comparison our AJA Hi5-3G's displayed the full range of the pluge pattern on every display.

Emails back and forth with BMD support, suggesting various settings came to naught, and a feature request. Eventually I sidelined the HDLink Pros, and deployed the AJA's where I needed a reliable HD-SDI-HDMI conversion. Obviously they're no help for applying a LUT.

I'll try a firmware update shortly on the HDLink Pros to see if there's been any improvement, and post back here if there's any love. If not, I'll drop an email to the address Steve posted above.

Author Steve
Scene
#23 | Posted: 26 Jul 2012 06:46 
Yep, that is as we have seen to...

We have still had no further follow-up from BMD, even after many e-mails and my promised of action from them.


Author Margus
Mono
#24 | Posted: 2 Aug 2012 10:23 
I just wrote to that email you gave and directly to BM support.

Will see if it helps.

Author Dermot
Mono
#25 | Posted: 3 Aug 2012 16:57 
sent a email off to Kristan more than a week ago, no reply as of yet

Author Steve
Scene
#26 | Posted: 6 Aug 2012 14:23 
Same here - no replies at all - and I've sent a number of e-mails...


Author Steve
Scene
#27 | Posted: 18 Aug 2012 21:13 
I've just been sent a quote regarding the HDlink pro where it was stated that:

"the HDLink Pro does work by has some issues that have to be worked around. It clips to video only range 16-235 64-940"

This is not correct, and the issues with the box have nothing to do with video/data levels. That actually works as it should.
The problems are with the LUT that is loaded being distorted by the box.
It is actually easy to prove this, as you can extract the LUT back out of the HDlink Pro box, and the LUT that comes back is significantly different to the one that was loaded.

I really, really hope BMD find a fix to this soon, as the box really is unusable for accurate LUT work as it stands.

Steve

Author melorama
Mono
#28 | Posted: 19 Aug 2012 04:19 
Steve
Steve:
I was working at a clients yesterday performing calibration, and spent more time looking at the HDlink Pro
Even in 'bypass mode' - no LUT active - the box distorts the image data being passed through it!
This was HDSDI in to HDSDI out, and the problem was easily visible in the shadows using the 'BrightnessCal' image available as part of the Calibration Images download from the Light Illusion website.

The box really is unusable in its present state!

I wanna make sure I'm reading this correctly:

Do you mean that all this time I've been grading images in Resolve, through the HDLink Pro (in unity/bypass mode, since I bought it only to convert the SDI out from my MacPro to HDMI for my Panasonic Plasma) and into a 709 "calibrated" display, my actual deliverables have not been accurate to what I've been seeing on screen?

I hate to be one of those "guys on the internet", but THIS IS AN OUTRAGE.

How can BMD in good conscious still be selling this box, if the "bypass" mode isnt actually bypassing it's internal color-processing system?

Author Steve
Scene
#29 | Posted: 23 Aug 2012 15:33 | Edited by: Steve 
Kristian, from BMD, has replied to a number of HDlink Pro users who have reported the problems mentioned in this thread.
The gist of the message received is as follows:

Yes, we plan to fix the problem.
Another user has sent through some waveform readouts that will help.
We aim to fix this after IBC.

So, if any other users can send info to Kristian it will help BMD locate and fix the problems.
They have the info I initially provided as well, but more should help.

Cheers,

Steve

Author Gabriele Turchi
Mono
#30 | Posted: 28 Sep 2012 20:47 
i guess no news on this right?
thanks
g

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