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Live Video "Micro Stuttering"


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I am having these problem now for years and wanted to ask the forum if someone has a workaround or solution for this:


I am inputing 720p50 or 1080p50 into various capture cards in various PCs and multitiple shows and always the same. (output is on 50 Hz and Show is on 50 fps in settings. Input with no frame blending or deinterlacing of course)


Inputs come direct from mixers or cams directly. Does not matter...


I use and used various card from BM, to No Name to Datapath (SDI, HDMI, DVI...). It doesn't matter.


Sometimes I get micro stuttering. It comes every few minutes and goes - otherwise it works smooth


Do I have to live with this forever? I am asking cause we just bought two new PCs (one for production/ one for Display) with 6 core CPUs and firepro GPUs and it's still the same - so "power" can't be the problem any more...


tried with/without frame blending/deinterlacing... what can I do to get a constant smooth live picture?




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  • Moderator

... Sometimes I get micro stuttering. It comes every few minutes and goes - otherwise it works smooth ...

With the settings you are using the CPU is bypassed and the capture stream is DMA'd to the GPU.

You might want to confirm your PCIe x16 GPU has not dropped back to x8 operation

due to CPU lane utilization in your system.

There are CPUs with limited lanes where adding even an x1 capture card

forces the GPU transfer speed downgrade.


Can you determine if the events are cyclic, i.e. Is there a relatively consistent time period between events?


Do the events occur during other periods of activity such as movies starting, multiple stills loading, etc.?


Are you sure all Windows background activities have been tuned out - no Windows networking, etc?


Have you tried operating in cluster mode to determine if that makes a difference?


BTW it always helps to indicate WATCHOUT and Windows version in troubleshooting queries.

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first. thanks for quick writing!


I did not add WO and Windows Version cause I am having the problem from 2008 when I started with Watchout in now the 5th or so renewel of our Display PCs with various versions of Windows.


But let's get into business with the current rig:

6 core CPU, Asrock X99 Extreme 4, AMD Firepro, SSD for Win, M2 SSD for WO, Capture Cards Vision SDI2 Datapath (4 lanes), Startech DVI (1 lane), Win 8.1, WO 6.0.2 (no, I can't update to 6.1 - cause there all the live Inputs are gone - other forum post)


Production PC is the same except the M2 SSD and the capture cards...


- the events are indeed cyclic and it sometimes occurs when I start the Live Input(I always insert the live video into a task I start (or better said: to preload, I press stop and then play)

I makes no differences if I use tweens on the live input or not ("Gain" e.g.)


but it is definitly periodic


- no there is no correspondence when other movies or pictures load... I am working with ProRes and HAP files and the performance overall got much better compared to H.264


- Display PCs are setup as advised in this forum - so i guess No Windows networking...


- No I did not operate in cluster mode cause I really need and appreciate the production interface.

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  • 2 weeks later...
  • Moderator

Hi, do you have the possibility to measure the time between the micro-glitches?


If the device generating the live video is not genlocked with the display computer then some microscopic glitches will occur due to the difference in refresh rates. Say that the captured device is generating images at 59.94Hz and WATCHOUT renders at 60.00Hz then WATCHOUT will insert a double frame every 16-17th second. In a very smooth animation this will look like a microscopic glitch.


Frame blending should smooth out this kind of frequency mismatches but if you don't want this feature then genlocking is the only way to go. Otherwise you will always get this issue since the source device is not perfectly synced with WATCHOUT (they use separate clocks). In your case the camera might actually output images at 49.995 Hz while WATCHOUT renders in 50.005Hz which will generate a glitch every 100th second (1.67th minute).


Best regards,



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