Basic information We do use MediaPlayerElement within UWP platform to play the videos. However, on some display devices, using closed captions (subtitles) leads to video lagging. Specifically, I was able to confirm that issue occurs on: Epson EB-G6570WU projector connected using HDMI Epson EH-TW9100 projector connected using HDMI Phillips 245E1 display connected using USB-C => DisplayPort cable Problem showcase Following recording displays the lagging while subtitles gets rendered: https://jandrozd.eu/files/20230906_015600.mp4 (6 MB). More information The lag seems to occur with each subtitles change. During testing I found the lower the display's refresh rate is, the lags get worse. When the subtitles are disabled, the same media file plays without issue. We tested to create our own subtitles parser and displaying engine. When it renders the subtitles over the MediaPlayerElement, it produces same bad behaviour as when we use the closed captions functionality of MediaPlayerElement (TimedTextSource). When we play the same video file using LibVLC with the same custom subtitles system (and on displays above), the video DOES NOT lag. Issue can be reproduced using different laptops Issue occurs in both full-screen and windowed mode Laptop information My device HW information: https://prnt.sc/tLx0ijf2Dqnx (issue occurs with different laptops also) I have nVidia RTX 3070 graphics card and have the latest drivers. The Windows system is up to date.

Closed captions of MediaPlayerElement causes video lags on some displays

Jan 6

Basic information

We do use MediaPlayerElement within UWP platform to play the videos. However, on some display devices, using closed captions (subtitles) leads to video lagging. Specifically, I was able to confirm that issue occurs on:

Epson EB-G6570WU projector connected using HDMI
Epson EH-TW9100 projector connected using HDMI
Phillips 245E1 display connected using USB-C => DisplayPort cable

Problem showcase

Following recording displays the lagging while subtitles gets rendered: https://jandrozd.eu/files/20230906_015600.mp4 (6 MB).

More information

The lag seems to occur with each subtitles change.
During testing I found the lower the display's refresh rate is, the lags get worse.
When the subtitles are disabled, the same media file plays without issue.
We tested to create our own subtitles parser and displaying engine. When it renders the subtitles over the MediaPlayerElement, it produces same bad behaviour as when we use the closed captions functionality of MediaPlayerElement (TimedTextSource).
When we play the same video file using LibVLC with the same custom subtitles system (and on displays above), the video DOES NOT lag.
Issue can be reproduced using different laptops
Issue occurs in both full-screen and windowed mode

Laptop information

My device HW information: https://prnt.sc/tLx0ijf2Dqnx (issue occurs with different laptops also)

I have nVidia RTX 3070 graphics card and have the latest drivers. The Windows system is up to date.

Junjie Zhu - MSFT 14,831 Reputation points Microsoft Vendor

2023-09-06T08:41:21.7433333+00:00

Hi @Jan , Welcome to Microsoft Q&A!

Can you reproduce your problem using the official sample? Could you please provide your code snippet about MediaPlayerElement?

Thank you.
Jan 6 Reputation points

2023-09-06T13:15:28.8933333+00:00
Hi @Junjie Zhu - MSFT .

I've downloaded the sample you mentioned and tried to reproduce the behaviour. The issue does not occur in your sample. I will be happy to provide our snippet, but the playback page code we use have 7500 lines of code...

The difference between official sample and our usecase is:

We use the secondary view (window) for playback

We use ProjectionManager to open the secondary window in fullscreen mode on selected display
Jan 6 Reputation points

2023-09-06T15:06:37.5066667+00:00
@Junjie Zhu - MSFT

I've prepared minimum reproducible sample. It can be downloaded from:

https://jandrozd.eu/files/PlaybackSample.zip (428 MB - it contains the code, the sample film file and subtitles file used to reproduce the issue)

You can see how the sample behaves on my displays in following video I recorded:

https://jandrozd.eu/files/20230906_170028.mp4
Junjie Zhu - MSFT 14,831 Reputation points Microsoft Vendor

2023-09-07T09:56:31.98+00:00

Hi @Jan ,

I can reproduce the same behavior, I will confirm this unexpected behavior with our Team.
Junjie Zhu - MSFT 14,831 Reputation points Microsoft Vendor

2023-09-12T07:45:06.72+00:00

Hi @Jan ,

For your scenario, I suggest that you might need to open a support ticket for this. Please contact our paid support at MS Support. You will get 1:1 support on that. Select Developer Tools -> Windows UWP Development -> Windows 10 Universal App Dev -> Graphics and Multimedia Development-> Media Foundation API in the support page and you could contact the team. Please kindly note that your support ticket will be free if it is Microsoft's issue.
Jan 6 Reputation points

2023-09-25T13:32:53.4033333+00:00

@Junjie Zhu - MSFT Hi. Thank you for the suggestion. Let me ask additional question regarding pay-per-incident support. You've stated that incident support will be free if it is Microsoft's issue. Does it mean that the payment for incident will be refunded or does it mean that we'll have prepaid support for another incident for the next year?
Junjie Zhu - MSFT 14,831 Reputation points Microsoft Vendor

2023-09-26T03:03:37.73+00:00

Hi @Jan ,

If it is Microsoft's issue, the payment for incident will be refunded.
Tamotsu Takahashi 0 Reputation points

2024-03-08T07:28:24.02+00:00

What is the current status of this issue?

I found an interesting reddit article. It says that one pixel of an always-on-top window fixes it.

Surely this is just a workaround. I hope it will help someone fix the problem in windows.
Tamotsu Takahashi 0 Reputation points

2024-03-11T03:55:58.5033333+00:00

Other information:

https://answers.microsoft.com/en-us/microsoftedge/forum/all/netflix-videos-stuttering-in-fullscreen-when/03d2b443-8a19-44ed-9626-36ba7c49ecb9 also says another window on top of the player suppresses the stuttering.

https://answers.microsoft.com/en-us/microsoftedge/forum/all/netflix-4k-videos-stutter-in-fullscreen-when/e24557c5-d1ae-4e81-a83c-2915e95fc3e6 says that the lower the refresh rate is, the worse the symptom gets. They are about Netflix player, but I think they are relevant to this issue.