severe video sync issue

DusX

I have been trying to follow this thread. Unfortunately I do not have the hardware to do a fair test myself.
If Fred is correct in how the Magwell capture works (sends video out the Computers CPU for scaling) then yes, it seems 2 streams is likely at least a peice of the problem. This could be solved by using hardware scalers, before capture. If the feeds are scaled to 720 before reaching the capture device, that will open up your bandwidth.

Lauri

@Fred Thousand thanks again for your test instructions! And my deepest apologies for this long long delay in replying – my schedule has gone up and down during these almost 2 months, truly sorry! I hope you would still be willing to go through my test results and give me feedback, if possible. And if needed, propose some further tests to be done.

There are some things I find a bit peculiar, for instance that the cycles usually stay up for a long time and suddenly start to sink and rise back again for long time. But maybe there's a simple explanation... Anyway, the test results became a bit extensive in length, so I thought to put them into a pdf, instead of posting it straight here.

IsadoraTests.pdf

Please, anybody, have a look on these.

@DusX Thank you for your comment too. It would be nice if a hardware scaler would be a solution. But again, while I used 2 Magewells, there was no dropped frames in the captured video files, only on the stage, and even on the stage the channels didn't mostly stutter simultaneously...

Any advice welcome, of course.

Thanks again in advance,

Lauri

P.S. also eagerly waiting for the new version!

barneybroomer

Is your wifi or any lan connection to the internet off?

Lauri

@barneybroomer Thanks for your reply!

When running a patch, I usually keep the machine disconnected from internet, if I don't need the connection with the patch.

barneybroomer

I read the PDF and I am pretty sure it is the Magwell's causing the problem. One thing that bothers me that if you do a recording in QT X it "sees" 720P, while you set the Maxwell to 1080P. That is already a sign. Are you able to set the recording in QT X in high res, next to the red rec button?

Furthermore the encoding from the Maxwell sends the CPU sky high, this is not normal. Sign 2...

Did you try another converter over thunderbolt for example? I have the same machine and capture with Black Magic Design, but all in 1920P, with no issues.

If you can wait for Izzy 3, it is promising. I test on a Macbook with external GPU with 6 beamers and one BMD input all in 1080P I/O , over one 40Gb cable, my Macbook is running under 10 percent.... 64 bit crazyness!

I have to test Izzy3 on the AMD700 as well, see if the GPU's will get in effect this time.

If I were you I would get my hands on a BMD to test over firewire.

DusX

@lauri said:

for instance that the cycles usually stay up for a long time and suddenly start to sink and rise back again for long time

This sounds like a potential conflict between your media framerates, capture devices framerate, and your output displays refresh rates.
If all match things should be pretty stable, but if they do not match you can see a rhythmic fluctuation.

Perhaps @Fred can share some insight. This isn't my strongest topic.

Lauri

@DusX Thanks for your reply. Yes, let's hope @Fred could comment on the results.

@barneybroomer It's my fault. I made the test3 without acknowledging how to set QT-X capture 1080p, so I have to make the test3 anew.

As told before, I have BM UltraStudio Minis, but I can get only 25fps out (well, 30fps also), there's no chance for 50fps, so they are not straightforward comparable. But yes, I will make a test with them too, and will report here, soon hopefully. I suppose, to compare the 25fps BM UltraStudios, I should make Isadora run 25fps also (instead of 50fps).

Fred

@lauri Hi, I don't have much time right now but I read through the PDF, as far as I can tell from the results, your system just cannot do this, it is not a fault with Isadora (seeing as though you get similar errors just using quicktime). I will try find a way to check a little further in the coming days. I think the next logical step is I can do some tests on my systems with a single magewell and see what results I get, mainly to check if it is a problem with Isadora (which so far from your results it is not). After that it is hard to find the actual bottelneck and with the computer you have you have very few options to use a different pathway (eg some kind of thunderbolt dock with usb 3 to get off the built in usb ports) and the machine is not upgradeable in any way.

Lauri

@Fred Hi, thousand thanks for your reply! No worries, take your time and reply when you have time.

I made a mistake with the test, as I wrote in my previous message. So, I made Test 3 anew with the correct capture settings in QT-X – there was no stutter, but please see the test results continued in the attached pdf.

In the same pdf, I added the Test 5, but made with Blackmagic UltraStudio Minis (although 25fps, instead of 50fps). And I get same kind of results as with Magewell. But, again, see the attached pdf.

IsadoraTestsContinued.pdf

Thanks in advance for all the help!

Lauri

Fred

@lauri Ill try to check it out in the coming weeks, I do have to say though that I have used multiple blackmagic capture units extensively on mac and PC with Isadora and not experienced any problems.

Lauri

@Fred Thanks for your reply! I have no doubt about that, but maybe the fault is somewhere else. @DusX proposed, there might be "a potential conflict between your media framerates, capture devices framerate, and your output displays refresh rates" or maybe the problem is something different. However, I'm still hoping there would be a solution.