Blackmagic Forum

Hi, wonder if anyone can help with this issue..
I'm running 3 x Sony FX30s into each Atem via a 10m Ugreen 4k/60Hz capable HDMI cable. The cameras are running 4K 25FPS 8Bit with the bitrate at 60Mbps
Whilst doing a live mix, I noticed on the my monitor that the feed on channel 3 was dropping out, dropping to black for a split 2nd every 30s or so.
After, I switched cameras around and didn't make a difference so it's not the cameras. I then switched HDMI cable and the issue changed from having drop out to having a 'speckling' effect around the lit areas. If I switched the cable to channel 1,2,4,5,6 or 8...it goes away but if it was in channel 3 or 7, I would see this every time.
I then switched the Atem itself to another unit and the problem went away this time.
I was then using another Atem in another room and noticed the same thing on channel 3, speckling across the screen as if data was being lost.
Is there some sensitivity in the Atem when combined with a pretty long HDMI cable that can cause this? Are the channels grouped in terms of processing? I never see this issue on channel 1 or 2..

regards
Ben

I use 50' and even 75' HDMI cables frequently. Not sure cable length is the issue.

Have you tried the new Fiber HDMI cables?
They are relatively cheap and can go 300 feet.

We had a 100' Fiber HDMI.

It was...spotty. Not reliable. (It was also relatively inexpensive.)

We went back to SDI.

Thanks guys for the feedback...still scratching my head here.
I've been switching consoles (have 4 in total) and I can now replicate the issue on channel 3 and 7 (haven't tried 5,6 and 8) on 3 of them. Can switch cables (all the same brand new) and cameras (same, all brand new FX30s) and still same. As it's intermittent it's time consuming as have to sit there watching it...waiting to see if it starts doing it.
Of course, a workaround could be to just use channels 1,2 and 4 for recording but, being an engineer, I hate not getting to the root cause!
My next test tomorrow is to try the other channels 5,6,8 (1,2 and 4 seem fine) and the switch the cameras down to 1080p from 4K and see if can turn the issue on/off...

regards
Ben

Jim Simon wrote:We had a 100' Fiber HDMI.

It was...spotty. Not reliable. (It was also relatively inexpensive.)

We went back to SDI.

It sounds like you had a bit of a mixed experience with the 100' Fiber HDMI cable.

As haven't been doing any live mix...not really looked into this but need to sort this so ran a trial today...most odd.

Had 3 x FX30 running on identical cables and Cam C causes horrendous flickering/speckling on channel 3 on the Atem, move to 4 and it's just speckling and then if I move the feed to 5,6,7,8 it generally gets worse (speckling but no flickering)

However, when I swap the HDMI cable from Cam C from channel 3 or 4 into channel 1 (and swap 1 into 3 (or any other), the problem goes away. I tried the same with another identical Atem and could replicate. Can turn the fault on/off

Of course, I then switched the cables between two cameras...and the problem completely vanished so suggests its some sensitivity issue with cable/camera combo and certain channels.

So basically, with 3 cams "A,B and C' in this one studio into channels 1,2 and 3 I see an issue with this camera C feed if it's fed into 2 or above. If I put this feed into Channel 1 on the Atem, it goes away (switching the original feed into any other channel so still have the 3 channels running)

I can't prove it's a cable issue yet (they are 18Gbit/s capable (apparently)) so ordering some 7.5m fiber optic units and then will back to back test....to see if can turn the fault on/off on channels 3-8 with a different spec cable.

Very odd though that the feed of this specific camera/cable is fine on channel 1 or 2 but not 3 or above...and I can replicate the fault with a 2nd identical Atem...

Inputs 1+2 have different circuitry and can be more tolerant with longer cables.

10m is on the threshold for copper cables. Especially at 50/60fps.

ManchesterV wrote:Inputs 1+2 have different circuitry and can be more tolerant with longer cables.

10m is on the threshold for copper cables. Especially at 50/60fps.

Oh, very interesting...that inputs 1 and 2 have different circuitry. I did wonder if there could be some variation and makes no sense why feed is perfectly fine on 1 and 2 and then crap 3-8.

Sounds very much like cables are borderline then, even at 4K 25FPS (60Mbps bit rate). Have some 7.5m fiber optic ones turning up next week so will see can turn problem on/off on channel 3.

Cheers for the help