Seeing dropped frames in playback

garret.linn

Been seeing a video playback problem
in both the last release and in the current beta

The material that I am playing is mostly cars going side to side and as such it is very easy to see drop frames

The video will run fine for about 3 to 4 minutes and then will drop a few frames and then usually recover… and then start dropping again a few minutes later

It seems to be similar to this report

Re: [playback movie stutters on slo-mo from fcp](/topic/8511/playback-movie-stutters-on-slo-mo-from-fcp)

I am running three screens that are being chopped out of a single threewide HD file

For running the three screens and sync — super simple and very basic set up. — Everything is set up properly. The output projectors are all set at 60 FPS and the video is 29.97 — The playback load is usually about 4% and isadora says that the playback FPS is rock solid

I have gotten the same results using both H264 files and ProRes files

At the moment, the only way to avoid the dropped-frames is to switch out of isadora and into another program every few minutes
(or going into the settings, while the show program is playing and changing the general service setting)

I started the project on a M1 max silicon, mini Mac using the latest release of isadora

Then tried using the current beta
Then I tried moving to an M2 Max PowerBook pro
I tried changing a couple of projectors, different audio interfaces, etc.

(i did not have an intel machine to test on)

On these machines with all versions of isadora, the end result was always the same

This does not seem to be actually a problem in isadora, but rather in the silicon Mac’s?

the dropout frames, don’t all happen on all three screens at the same time, but rather screen number one will sometimes get dropped out frames, sometimes screen two, or screen three — The dropped frames never occur synchronously on the output.. it always randomly on one or two of the screens.

My general feeling is that the system itself is trying to move, perhaps from performance cores to efficiency cores? Or perhaps the ProRes engines in the silicon Macs are causing the CPU to do so little that the system tries to move into a low-power mode?

As I said, before, switching from isadora to another active program, in my case, I was running resolve in the background
I did this hoping to force more cpu cycles to get used— helped but I have to actively switch from back and forth from one program to the other
Just having Resolve running and keeping Isadora in the front was not enough

Any thoughts?

Anyway to make sure the movie player is getting full use/priority of the system?

Woland

@garret-linn

If you don't need to actively be on the computer doing other things while this is running, it sounds like downloading and running a mouse jiggler application could solve this for you.

garret.linn

thanks for the feedback and advice

sadly "Mouse wiggling" alone is not enough... ( I did try that... )

only switching to another (a heavy video program) or changing settings in Isadora would trigger the proper "resync" of the frames...

and remove the "Glitching" or lost frames (really more resetting play back)

again this was a simple three screen patch - That Izzy should really have this down pat... I'd be super happy to do some detailed reporting.. logs, patches, etc...

I've been away from the Isadora world for a while
but these sorts of problems were common in the move from Coca to AV Framework

it reminds me of that era... and sadly was the reason I moved away from recommending Isadora (back then)

this problem came up in a gallery museum setting where perfect playback is more important than say -- interactivity
I do have another project coming up in the coming months that is a four screen playback .. I hope to start testing in the next couple of weeks

Garret

Fred

@garret-linn one thing extra to check, it would be good to understand exactly how your screens are connected and with what brand adaptors. There are USBC to hdmi adaptors that require extra overhead.

Mostly adapters that only have a single purpose support alt mode on the usb port. This means that the USB port will directly transmit display port data from the GPU, even though it is a USB port. Other adapters and especially docks or adaptors with more than one kind of port, may not support alt mode and may require an additional layer of overhead to feed a screen.

Keeping the system video buffers in sync with Isadora’s internal buffering, for multiple screens, when not all the devices are the same may cause errors like the one you have been seeing. Especially if the solution is to reset Isadora’s video settings (and the buffer it feeds to the system).

Woland

@garret-linn

Try going to Isadora Preferences > General > Frame Rate/Tasks > Display Refresh > Off

If that doesn't work, please open a support ticket as we may have a solution for you in the beta.

garret.linn

@fred

I tried with a number of Both HDMI adaptors and Display port

in the end I was using Blackmagic Hdmi to SDI

so that I could confirm that All Screens were really running at a fixed and true 60Hz

Garret

garret.linn

@woland

Hi ya

so "Display Refresh > Off" would do the same thing as changing the general service from 4x to 6x

Or the same as clicking on another running (video) program...

That is to stay it would eliminate the stutter

but after anywhere between 1 and 3 minutes it would come back

I will enter an official support ticket today!

Thanks all

Garret

Fred

@garret-linn Hi, your computer only has a single HDMI out.The other 2 outputs (you mention you are running 3 screens) need to be attached to the USBC/thunderbolt connections. How are these connected and with what brands and kinds of connections. Are all your screens the same and running at the same frame rate and refresh rate?

If you leave the 3 screens connected and active stages in Isadora but play the video on one screen does is still give the error. Can you try this for each screen (send a test signal via Isadora to the other screens)

garret.linn

@fred

thanks for the help Fred

I have tried many combinations of outputs: (and different computers both m1 and m2)

the native HDMI + usb-c to HDMI (adapters)

all Displaylink connectors

a combo of Displaylink (Pluggable interfaces using the DP drivers -- and the native HDMI)

all tested to both mixed projectors directly and via identical blackmagic HDMI to SDI converters

in all cases the result is the same (no combination was better or worse)

I get dropped frames on each screen separately and not on "one screen"
nor do I get synchronous errors across all screens (they happen randomly on all three screens after about two minutes)
such I do not believe it is the connections

Rather I think there is an error occurring in the system (it really may not be an Isadora fault - but rather a system OS problem)

My opinion is that there is some event in the control of the Thunderbolt Buses that is causing it to change "priorities" of service
Isadora is only using a small tiny percentage of the CPU or GPU -- so small that the OS may think it's ok to move to efficiency cores (?)

(we have seen something like this before in the move to AVfoundation in the past)

I am in contact with troikatronix and they seem to think there might be a fix to be had in a new beta release

I have not tried leaving the connections up - but only connecting one screen -- I will do later today

thanks

Garret

PS - for "most" video this would not be seen - in my case the video source is fast moving objects (cars) moving across screen as such any and all frames lost are easy to see)

so yes this is an edge case

garret.linn

@fred

yeah I tried your request

"If you leave the 3 screens connected and active stages in Isadora but play the video on one screen does is still give the error. Can you try this for each screen (send a test signal via Isadora to the other screens)"

and sadly the same problems

nice thought though

G

Fred

@garret-linn to clarify my earlier question. What brand of converters are you using to get from usb c to hdmi. Are they all single purpose (just usbc to hdmi, no other ports) and apple branded?

garret.linn

@fred

To my knowledge Apple does not sell a usb-c to HDMI (they resell Belkin)

I used a few different types

and I tried a few that I didn't not know the manufacturer

nothing changed via hdmi or Displaylink (Pluggable)

G