NDI flicker

django

Hi!

Have now used Isadora for a couple of remote performances, and completely loving the experience!

Just wanted to look into one issue I had when using NDI output (which has been needed a few times) -- still frames often have a tiny flicker. I wasn't sure if it was a frame rate thing or something, but decreaseing frame rate didn't seem to affect it.

It's quite subtle, and I'm sure it's not noticeable for an audience... but was hoping to get to the bottom of it, because if it's something I can fix on my end I'd love to know!

Here's a GIF zoomed in on some Izzy subtitles as an example (sorry for reduced quality, seems like the easiest way to demo):

I haven't had the issue in Spout, so I'm guessing its something about the switch to NDI.

Many thanks and all best,

Django

liminal_andy

@django I sometimes encounter this as well. Out of curiosity, what does studio monitor report as your output framerate?

django

@liminal_andy studio monitor says 119.88i, which I now realise has been referenced in a previous community post.

django

https://community.troikatronix...

Looks the workaround is to use SpoutToNDI

liminal_andy

@django I ended up having to do that, too

Juriaan

I am also wondering what your cycles and fps is when you are using that patch?

django

@juriaan I'm getting around 177 ish on cycles, and then 24.8 - 25 fps (target frame rate is 25fps)

SpoutToNDI works! Also Spout output instead of NDI output really lightens the load on Izzy, so might just be a better option in general.

Hopefully the default NDI output framerate gets fixed soon.

Best, Django

mark

@django said:

Hopefully the default NDI output framerate gets fixed soon.

It's fixed in the internal beta. The next Isadora version will primarily be a compatibility update for Big Sur (Intel only for the moment). But fixes like this will be included.

Best Wishes,
Mark

mark

@django and @liminal_andy

Here's a GIF zoomed in on some Izzy subtitles as an example (sorry for reduced quality, seems like the easiest way to demo):

I will investigate this.

I am aware of the slowness of NDI output. Isadora is based around OpenGL and this means that pulling data from the GPU back into the CPU (necessary to send frames to NDI) which is necessarily slow. SpoutToNDI might work better because it uses Windows' DirectX to pull the textures back into the CPU, and that might offer better performance. (Also the fact that it's running as a separate app might provide better isolation in terms of slowing down the pipeline.)

Best Wishes,
Mark

liminal_andy

@mark This is a good solution but it does retain some issues. I have found that the converter to NDI can cause frame jumping if Isadora reports that is is slipping from its target frame rate due to increased load (versus just stuttering at a lower FPS), such as during a scene transition. Here is a time-stamped example from a client (sometimes the time stamp does not take on this forum, looking at 58:40), who used Isadora and the Spout/NDI bridge for the show:

liminal_andy

I will be very curious to see if these SAM technologies as well as the shared memory layout of the M1 make their way into NDI and live video pipelines in the near future:

https://www.tomshardware.com/n...