Film-Tech Forum ARCHIVE: Flashing black frames - Barco DP4k-19B

This is topic Flashing black frames - Barco DP4k-19B - HDSDI input board in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Nat Jencks (Member # 10863) on 05-01-2019, 11:19 PM:

Hi folks, first posting here, thanks in advance!

We are experiencing an issue with a new DP4K-19B projector being used in a post production environment where we are seeing occasional flashing black frames when receiving 2K input via HD-SDI. Might effect 4K also we just haven't seen it.

We have reseated the boards, and even re-flashed the ICP board. We have swapped cabling to confirm its not cabling related, and we are seeing this same issue from three different playback devices.

The only clue we have so far is when we go to Diagnostics/Tests/VideoPath/Timing Information using Barco Communicator we see two columns for each of the 4 SDI input links, the “detected timings” and the “VPID” column. During our testing it looks like when the problem is happening the “VPID” column that one would expect to be filled with info about the incoming signal is blank, and when the problem is not happening the VPID column is filled with the correct information.

This seems to me like perhaps the SDI inout board might be failing to adequately lock sync with the incoming video signal.

The problem is very inconsistent. Looping a section of video that is triggering the problem will repeatedly trigger the issue, and then unplugging the SDI cable and re-plugging it will solve the issue.

Has anyone ever seen anything like this?

Best-
-Nat

Posted by Paul Finn (Member # 10726) on 05-02-2019, 06:53 AM:

I have seen this with SDI video under other conditions/situation. If you have a SDI line amplifier or repeater or other separate SDI pass through piece of hardware that re-clocks the video stream, place one of these units between the source device and the projector input. This may solve the issue.

Another possibility is the AC power source(s)to the equipment may cause a clocking issue between them if there is a power phase difference which the separate units are using for clocking reference. One piece uses single phase power and the other uses three phase power, for example. This discrepancy can also happen when switching power supplies are involved in the affected equipment. Again an intermediate device may solve the issue.

Paul Finn

Posted by Marcel Birgelen (Member # 6801) on 05-02-2019, 01:10 PM:

What is the output source of the HD-SDI signal? If the VPID goes missing in action, that's more an indication of a problem with the source rather than the playback device (in this case, your projector).

Posted by Stephan Shelley (Member # 8587) on 05-02-2019, 05:56 PM:

You should check the SMPTE errors. If they are high check cables and video connection.

Posted by Nat Jencks (Member # 10863) on 05-02-2019, 08:29 PM:

@Marcel thanks for the reply! We have seen the problem when using multiple playback devices (three different systems, DVS Fuze, Colorfront Transkoder, and Davinci Resolve) on three different hardware systems, some using AJA video i.o hardware and some using BMD i/o hardware. We have also tried swapping the cables being used for A and B links to rule out the possibility that the "A" cable was bad. All these signals are going through a BMD SmartVideoHun 40x40 12G router.

@Stephan thank you! When you say check the SMPTE errors do you mean the errors that are logged for each link in Barco communicator under Diagnotics/Tests/Video path?

There are some errors logged on these lines but we were under the impression that was normal... what is a normal # of errors to expect on these lines? Thank you!

Thanks for the feedback!

Posted by Stephan Shelley (Member # 8587) on 05-02-2019, 08:42 PM:

Yes those are the errors I am talking about. should be close to zero. I think you should be able to reset it. Other than a few at the start of the day should not go up after that during the day. How long are your cables? At one time short cables were an issue. Everyone used 50 foot cables even for a short run.

Posted by Nat Jencks (Member # 10863) on 05-02-2019, 11:00 PM:

Thanks Stephan. We *are* seeing a fair number of errors on the lines but that might be because of our use case where we are often changing signal to the projector by changing the source being sent over the router, changing from 2K to 4K, etc since we are in Post Production.

We had the error happening over and over again yesterday with a chip that was triggering it on loop and we watched the projector flashing but we were looking at the errors and it wasn't going up even though continuous update was checked.

Posted by Nat Jencks (Member # 10863) on 05-05-2019, 01:13 AM:

@Paul, that's interesting, thank you for the feedback! In this setup the projector is on 3-phase and the playback devices (in a separate machine room on a different floor) are on regular 110V. But surely the projector has its own digital timing circuit to lock to the incoming SDI that is totally independent of the type of electricity powering the unit?

Playback devices are routed through a blackmagic design 40x40 smart hub router which does reclock SDI. We have never seen these black frames when playing any of these different sources to other displays or projectors (we also have an NC800 and NC900).

Thanks for the feedback!

Posted by Nat Jencks (Member # 10863) on 05-07-2019, 11:23 PM:

Just heard from another Post Facility that had a similar issue. Flashing black frames when in 2K but not in 4K. So strange