Screen Flickering IMX8

Question

Hello :),

I was experimenting with the i.MX 8M Nano EVK and Embedded Wizard.

I've installed everything according to the documentation (https://doc.embedded-wizard.de/getting-started-imx8-opengl-wayland?v=11.00)
The image on in i.MX is the Multimedia Image (imx-image-multimedia) with Wayland.

I have the following setup:
Windows Host
Ubuntu VM (Yocto and SDK)

I can build a binary on the VM and copy it to the i.MX8. There I can sucessfully execute it. Great!

Here is the problem: Whenever something changes on the Screen of the i.MX8 (e.g. a Slider moves) the whole screen is flickering until the animation plays out.
So everytime something changes on the display, it will flicker.

How can I fix that?

Regards, Oliver

Answer 1

Hi Oliver,
I verified the IMX8-OpenGL-Wayland package on i.MX 8M Mini EVK without any flickering.
Have you already tried to run another OpenGL based application on your i.MX 8M Nano EVK?

There are two option flags in ewconfig.h that maybe can improve the reported behaviour:

• #define EW_PERFORM_FULLSCREEN_UPDATE           0
• #define EW_PERFORM_FULLOFFSCREENBUFFER_UPDATE  0

Please set both options to 1 and rebuild the application.

Regards, Martin
 

Comments

Hello Martin,

thanks for the tip. I've edited the config file to the following settings:

#define EW_VIEWPORT_AUTOSCALE                  1
#define EW_PERFORM_FULLSCREEN_UPDATE           1
#define EW_PERFORM_FULLOFFSCREENBUFFER_UPDATE  0

And now the flicker is gone :)

Is there any documentation for these settings and what exactly they do?

Regards, Oliver

---

Hi Oliver,
nice to hear that it works now.
Does it also work with EW_VIEWPORT_AUTOSCALE = 0 ?
Both options are described briefly in '\Application\Source\ewconfig.h'.
However, I'm wondering what is the difference between i.MX 8M Mini and Nano EVK regarding this issue, since both options are not needed on my Mini EVK.
Normally it depends on the egl/opengl implementation, whether such options are needed or not. But I think it shouldn't be different between them.

Regards, Martin

---

Hello Martin,

Does it also work with EW_VIEWPORT_AUTOSCALE = 0 ?

Yes, autoscale is only enabled because the application does not fully fill the screen without it.

However, I'm wondering what is the difference between i.MX 8M Mini and Nano EVK regarding this issue, since both options are not needed on my Mini EVK.

I have a few guesses, but nothing certain. In increasing order of likelihood:

1) Unlikely: Yocto Image. I used the imx-image-multimedia image. Maybe you used a different one?

2) Maybe: According to the NXP Documentations Mini and Nano have different GPU 

1. Mini 
   • GCNanoUltra + GC320
2. Nano 
   • GC7000UL

 and VPU 

1. Mini: 
   • 1080p60 VP9 Profile 0, 2 (10-bit) 
   • 1080p60 HEVC/H.265 Decoder 
   • 1080p60 AVC/H.264 Decoder 
   • 1080p60 VP8 
   • 1080p60 AVC/H.264 Encoder 
   • 1080p60 VP8 
   • TrustZone support
2. Nano:
   • None

3)Possibly: Otherwise maybe the Display is the culprit? Since the examples are in 480x272, 800x480 and 1280x720. I ordered a small 8" display from amazon (Amazon Link). This has a resolution of 1280x800, maybe thats the reason?

 

Regards, Oliver