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daveyijzermans  
#1 Posted : Saturday, August 4, 2018 5:00:42 PM(UTC)
daveyijzermans

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Hi!

I'm still awaiting the release of the Magewell Flex 4 input/2 output card, and wondering if I should order it. I currently have a Blackmagic Duo 2 card and haven't been able to actually try a Magewell card ever before.
Wondering if there's anyone here that can measure the difference between capturing with Decklink and capturing with Magewell (preferably with and without the "Low Latency capture" option in vMix)
I'm hoping even for an improvement of 2 frames, but as of now I know nothing yet: haven't found other information online and my local resellers also don't know.

Thanks in advance if you're able to test this for me.

Kind regards,

Davey.
zenvideo  
#2 Posted : Monday, August 6, 2018 7:28:31 PM(UTC)
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daveyijzermans wrote:
I'm hoping even for an improvement of 2 frames, but as of now I know nothing yet: haven't found other information online and my local resellers also don't know.

I shouldn't think you'll get a two frame improvement because I don't believe that either card (Magewell or Blackmagic) contributes as much as two frames of latency at the capture stage, so there's not a 2+ frame capture latency there to be eliminated. At best (in theory) the low-latency mode can reduce latency in progressive signals by almost a frame (or by almost half a frame for interlaced signals). As for the Flex I/O cards, samples were first introduced at IBC last year, but I have no word as to when they will be available. Hopefully more news will be forthcoming at IBC in a little over a month. I believe that there's been a bit of a rethink on the internal design which has caused the delay.
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daveyijzermans on 12/28/2018(UTC)
mjgraves  
#3 Posted : Tuesday, August 7, 2018 12:07:26 PM(UTC)
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I may be worth mentioning that there are certain limits to reducing latency. In a traditional broadcast chain there may be zero latency. That implies that no device in the chain has to frame sync the video. It further implies that all the devices are genlocked to a common reference.

If a source is not genlocked the device receiving the signal must resync it, which introduces a frame of delay.

I've noticed that when creating complex composites in vMix there amount of latency may also increase as the layering gets more complicated.
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daveyijzermans on 12/28/2018(UTC)
JoseL  
#4 Posted : Wednesday, August 29, 2018 7:07:09 AM(UTC)
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On my tests basically same latency with magewell or blackmagic. In fact i think blackmagic has less latency with progressive signals than magewell, difficult to measure because is 1f or less difference.

Genlock do nothing for capture and is not needed. Asap signal is comming it is captured and processed, no need to sync with others. Genlock is for blackmagic output, to send signal at same "time" than other signals when it comes to a switcher or mixer, that way you will get one less frame on the mixer input.

In my test "low latency mode" and normal mode same latency... maybe i need more complex compositions...

regards,

Jose.
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daveyijzermans on 12/28/2018(UTC)
daveyijzermans  
#5 Posted : Friday, December 28, 2018 4:09:40 PM(UTC)
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Thanks for the replies in this thread! Helps me realize what I can and cannot expect from a software switcher.

Originally Posted by: JoseL Go to Quoted Post
On my tests basically same latency with magewell or blackmagic. In fact i think blackmagic has less latency with progressive signals than magewell, difficult to measure because is 1f or less difference.

Genlock do nothing for capture and is not needed. Asap signal is comming it is captured and processed, no need to sync with others. Genlock is for blackmagic output, to send signal at same "time" than other signals when it comes to a switcher or mixer, that way you will get one less frame on the mixer input.

In my test "low latency mode" and normal mode same latency... maybe i need more complex compositions...

regards,

Jose.


Sorry for my delayed response...

If I understand correctly, you've tried both Blackmagic capture cards and Magewell capture cards with and without the Low-Latency Mode and there was no difference in latency?
That's a bummer, I was saving to get a Magewell card but I guess that's not going to improve things.

Do you mind me asking which cards you have and which graphics card you used for this test, if you remember?

Thank you!

Kind regards,

Davey.
JoseL  
#6 Posted : Saturday, December 29, 2018 9:07:59 AM(UTC)
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I didn’t test all magewell cards, only procapture quad sdi and dvi.
Depend of format interlace/progresive latency can be different between decklink/magewell. In all my tests decklink has same or less latency than magewell.
I use different decklink, quad2, duo, 4k... all has same latency.
The bigger difference from magewell/blackmagic is supported formats, blackmagic do not like some 3g sdi formats.
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daveyijzermans on 1/1/2019(UTC)
daveyijzermans  
#7 Posted : Tuesday, January 1, 2019 8:54:02 AM(UTC)
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Originally Posted by: JoseL Go to Quoted Post
I didn’t test all magewell cards, only procapture quad sdi and dvi.
Depend of format interlace/progresive latency can be different between decklink/magewell. In all my tests decklink has same or less latency than magewell.
I use different decklink, quad2, duo, 4k... all has same latency.
The bigger difference from magewell/blackmagic is supported formats, blackmagic do not like some 3g sdi formats.


Thanks again for your response. I bought a second DeckLink Duo for my computers, instead of the Magewell. From input to graphics card output I get 3 frames delay (@25fps) so it's quite acceptable)

I have found this option "Display Method" in the vMix advanced settings. Have you every tried this low latency option as well?
Don't know if it makes a diffference.

(VMware was used to quickly make the screenshot on my Mac, it is not my production system)

Schermafbeelding 2018-12-31 om 23.51.26.png (111kb) downloaded 0 time(s).
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