topic Re: IMX6. Start of Qt5 application causes flicker and tearing of camera preview on background framebuffer in i.MX Processors

IMX6. Start of Qt5 application causes flicker and tearing of camera preview on background framebuffer

maximkuk — Tue, 19 Jun 2018 11:04:12 GMT

Hello!

I use Freescale sabresd board with imx6q. My goal is to run camera preview as early as possible, so I modifyed mxc_v4l2_capture driver to start overlay task right after load and find camera. After that, when kernel completly loaded, I start GUI - qt5 application on fb0 (camera preview already running on fb1). I use eglfs plugin. The problem is that fb1 begins tearing when qt application starts. Can I force qt to use vsync of fb1? Or there are any other solution?

And another problem: fb0 have short one-time flicker when qt app starts (but fb0 set to fully transparent by default and it should not appear on top of fb1 until global alpha is disabled, right? I turn on local alpha blending on Component.onCompleted() signal of QML window). How can I start GUI more smoothy?

If there is a way to not flicker on GUI start, I can simply stop overlay task and run camera preview by gstreamer itself or qml from user space.

I attached video of my device booting. First appears camera preview on fb1 - no tearing, then one-time flicker, fb1 begin tearing, then appears test qml scene - background should be transparent, but it black in first time.

Re: IMX6. Start of Qt5 application breaks vsync of camera preview on background framebuffer

maximkuk — Tue, 26 Jun 2018 07:17:17 GMT

Tearing of camera preview begins after any framebuffer configuration, not Qt application itself. To avoid it, we can add MXCFB_WAIT_FOR_VSYNC ioctl before ipu_queue_task() in function csi_buf_work_func() in ipu_fg_overlay_sdc.c, but it redueces framerate. May be I can add MXCFB_WAIT_FOR_VSYNC in other place, somewear in framebuffer configuration.

But how can I avoid flicker on GUI start?

Re: IMX6. Start of Qt5 application causes flicker and tearing of camera preview on background framebuffer

igorpadykov — Tue, 26 Jun 2018 23:36:55 GMT

Hi Maxim

what bsp used in the case, please try official Demo Images on link

i.MX Software|NXP

Best regards
igor
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Re: IMX6. Start of Qt5 application causes flicker and tearing of camera preview on background framebuffer

maximkuk — Wed, 27 Jun 2018 14:10:00 GMT

Hello! Thank you for reply!

I use yocto BSP from fsl-arm-yocto-bsp.git, linux kernel 4.9.11.

I will try Demo Images and report the result.

May this issuses be caused by incorrect fb or display configuration? My display is SVGA050 800x600 and I add its configurations to device tree and mxc_lcdif driver:

mxc_lcdif.c:

{

/* 800x600 @ 60 Hz , pixel clk @ 24MHz */
"SVGA050", 60, 800, 600, 41666, 1, 7, 10, 10, 60, 2,
0,
FB_VMODE_NONINTERLACED,
0,}

device-tree:

&mxcfb1 {
disp_dev = "lcd";
interface_pix_fmt = "RGB24";
default_bpp = <32>;
mode_str ="SVGA050";
late_init = <0>;
status = "okay";
};

lcd@0 {
compatible = "fsl,lcd";
ipu_id = <0>;
disp_id = <0>;
default_ifmt = "RGB24";
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_ipu1>;
status = "okay";
};

Re: IMX6. Start of Qt5 application causes flicker and tearing of camera preview on background framebuffer

maximkuk — Thu, 28 Jun 2018 07:29:06 GMT

Hello! I have run test image from youre link (kernel 4.9.11, imx6q-sabresd.dtb, qt5-validation-imx-fb rootsf) with hdmi to not corrapt it by my configurations.

When I start Qt5_CinematicExperience it fills screen black, and after short time app screen appears. in console it prints: libpng warning: "iCCP: known incorrect sRGB profile"

When I start my test Qt application it fills screen black, and after short time app screen appears. No errors in console.

environment variables QT_QPA_EGLFS_PHYSICAL_WIDTH and QT_QPA_EGLFS_PHYSICAL_HEIGHT set to real screen size, QT_QPA_EGLFS_FB=/dev/fb2, FB_MULTI_BUFFER=2 (setting FB_MULTI_BUFFER to greater values not changing situation, if set it to 1 screen will freeze on first frame)

framebuffer settins:

root@imx6qpdlsolox:~# fbset -fb /dev/fb2

mode "1920x1080-60"
# D: 148.500 MHz, H: 67.500 kHz, V: 60.000 Hz
geometry 1920 1080 1920 4320 16
timings 6734 148 88 36 4 44 5
hsync high
vsync high
rgba 5/11,6/5,5/0,0/0
endmode

How to not filling screen black before QML scene will be shown?

Re: IMX6. Start of Qt5 application causes flicker and tearing of camera preview on background framebuffer

yyuan — Sat, 13 Jul 2019 02:40:12 GMT

please how do you output qt above video?

thank you

Re: IMX6. Start of Qt5 application causes flicker and tearing of camera preview on background framebuffer

maximkuk — Wed, 17 Jul 2019 10:12:21 GMT

Hello!

I draw qt to fb0 with local alpha turned-on and show video on fb1 by gstreamer or v4l2 video overlay.

Or you may configure QtMultimedia and use QCamera in qt scene.

Re: IMX6. Start of Qt5 application causes flicker and tearing of camera preview on background framebuffer

yyuan — Wed, 17 Jul 2019 12:59:05 GMT

thank you

i will try

thank you

Re: IMX6. Start of Qt5 application causes flicker and tearing of camera preview on background framebuffer

yyuan — Thu, 18 Jul 2019 01:12:15 GMT

please again

if do like you say, i want to know how to store fused qt and video together, So whether the combined qt and video can not be saved?

do you know ?

thank you very much again

Re: IMX6. Start of Qt5 application causes flicker and tearing of camera preview on background framebuffer

maximkuk — Thu, 18 Jul 2019 09:47:23 GMT

you can draw qt to some buffer and combine it with video by gstreamer. Or show video by qt and grab content of framebuffer.

Re: IMX6. Start of Qt5 application causes flicker and tearing of camera preview on background framebuffer

yyuan — Fri, 19 Jul 2019 00:53:49 GMT

thank you

I don't quite understand, i must thank it over.

thank you very much