Video Tearing / Decklink Quad Reference Input Problem

Hi All

Here is my setup

Mullumin 2 in Sonnet xMac chassis. Contains 2 Decklink Quad cards. (even though I'm only using one)

One Canvas running 4200x720

Using 3 SDI outputs running to a Spyder, then running DVI to led Wall to create 1 single wide screen.

Originally I didn't have the genlock running to the decklink cards, and they were very clearly out of sync. I pulled out a BM mini sync generator, ran it into both cards and into the spyder (although shouldn't be needed on the spyder). 

I have tried both 1080i 59.95 and 720p 59.94, just to try other resolutions, and I'm still getting some tearing between the 3 outputs. The sync between the outputs got visibly better after running sync into the cards, but its still not perfect. They roll in and out of sync between the 3 outputs, so at times it looks perfect, but at times it doesn't.

Spent an hour on the phone with black magic, and they don't have a clue (the tech was also dumber than a box of rocks). I'm a decent spyder opp, so I'm fairly certain the problem isn't with the sypder. 

Any thoughts? I have show in 4 hours, and kinda desperate to get this perfect. 


  • Hello @zhpittman,

    Did you had experience with chassic and synchronization before ? I'm not sure that 3 feeds could be handled correctly, through Thunderbolt 2.

    Millumin V2 is using a different method to output video to Blackmagic card, than Millumin V1.
    This is the method recommanded by Blackmagic to limit latency (since there is always latency with such cards, in comparison with direct output from Thunderbolt or HDMI), but should be in sync (however, I don't know if chassis has not an impact).
    The other method (the one in Millumin V1) has higher latency, but it fills the buffer of the Blackmagic card with 3 frames first. So it may change something in your case (limited rate via Thunderbolt 2).

    So you could try with Millumin V1 if there is a difference.
    Another try, and it should be more suitable in your case, you could use BlackSyphon with Millumin V2.
    Last try, use your 2 Blackmagic devices : splitting the output signal through 2 Thunderbolt buses could help the transfert.

    Unfortenatly, it's just alternative methods. It could or couldn't change something.
    Try first with 2 monitors, then add the 3rd one if everything is working.

    Lastly, and if you have time, be sure to check the outputs of your Blackmagic device with monitors, not the Spyder directly. It could give you some hint.
    Best. Philippe
  • Thanks for the info Philippe, 

    I don't see how 3 outputs would be more than thunderbolt 2 can handle. I can use Softrons Movie recorder with their M/80 package (8 input delta cast in a thunderbolt to pci box) and record up to (8) 1.5 gbps 1080p30 streams at ones. Seems outputting 3 1.5G video feeds would be well within the limitation of thunderbolt 2. 

    Just want to clear up, even though I have 2 decklink quad cards installed, I am only using one quad card to preform the 3 outputs.

    I Just tried using Millumin 1, and same thing. 

    I have no way to monitor them outside spyder effectively, since the delay is way less than 1 frame, but just enough that when motion is run across the seam, it is visible. We hooked up 2 monitors to it, and were not able to really see the delay with the naked eye, since the bezels of the monitor were separated the image too much.

  • Hello @zhpittman,

    Take a solid-color layer, and move it shakes it up and down in the middle of your canvas : if there is some tearing, you will see it, even if monitors are LCD.
    A more sophisticated method would be to take a picture with a timecode-movie duplicated on both your monitors (use a "copy layer" to do so).

    Is Millumin's framerate steady at 60fps (select "Display FPS" from menubar) ?
    Did you try BlackSyphon ?
    Did you try to use only 2 outputs, each one on a different Decklink ?
    Is such a configuration was working by the past (on macOS or Windows) ?

    Millumin is pushing all frames to Blackmagic at the same time, but we don't know how it's handled later on.
    Best. Philippe
  • So I tested monitors directly out of the BM cards. Same problems. 

    I tested it with Black Syphon, same thing, only 5 frames of delay more to the whole system.

    I checked the framed rate. When starting, FPS would drop to 57-58 for a brief moment, but hold steady at 60 FPS after. 

    The timing issues seems to come in on the left seam for about 10 seconds, then disappear, then the timing issue will be on the right seam for about 10 seconds then disappear. Its like its rolling in and out of sync.

    I have done this type of setup before with 4 outputs on one card with no issue. Mac
  • Hello @zhpittman,

    What were the exact conditions of your successful setup (with 4 outputs on one card) ? What were the softwares involved ? What ws the version of the Balckmagic drivers ?

    Did you try to use only one card on your failing setup ?

    What do you mean by "only 5 frames of delay more to the whole system" with BlackSyphon ? Do you have more with Millumin V2 ?

    Sorry, it looks like an hardware problem (not a software one, since Millumin V1 and BlackSyphon has the same issue, and we all use the same method more or less). Did you address a question to Blackmagic support via email (they are usually very responsive, and often the reply comes from engineer team) ?
    Best. Philippe
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