Re: [Interest] Efficiently render QtQuick-scene and encode to H264 on i.MX6 VPU?

[Ola Røer Thorsen]

Small update, it turns out GL_viv_direct_texture can only be used to upload
textures to the GPU, not the other way around. I did try this out to be
sure, no success.

The recommendations I get from NXP is to use their "virtual framebuffer"
kernel module, that creates as many virtual framebuffers I'd like. These
are only buffers in memory that can be read on the cpu side.

So now my question is this: is it possible from a Qt application to render
to more than one frambuffer at the same time? How can this be done, in
combination with QQuickRenderControl (I need to control the framerate)?
I still need to render to /dev/fb0 for my regular GUI (regular LCD screen),
but now I also need to render a window to one of these virtual framebuffers
("/dev/fbX", X > 0).

If this is not possible then I'll try to run that application as a separate
process setting the environment variable QT_QPA_EGLFS_FB to my virtual
device. I'd like to avoid this if possible.

Cheers,
Ola



2018-03-23 9:12 GMT+01:00 Ola Røer Thorsen :

> Hi Gunnnar,
>
> thanks a lot, this gives me a good starting point. I didn't know I could
> use GL_viv_direct_texture "in reverse" like this, I'll try it out. Already
> using it to stream decoded h264 video to a texture for rendering to the
> screen.
>
> I don't know which one will work best, but you want to avoid the
>> QOpenGLFrameBufferObject -> QImage conversion at all cost :)
>>
>>
> Yeah that's the one I was worried about :)
>
> Cheers,
> Ola
>
>
>
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Re: [Interest] QCameraInfo & Qt 5.10.1

[Igor Mironchik]

Guys,

So much regressions in QCamera in Qt 5.9 and 5.10... Don't remember in 
what version all was ok, but now this is something horrible to work with 
QCamera in Linux. What was changed?



On 23.03.2018 12:47, Igor Mironchik wrote:

Hello.

Let's say I initialized QCamera with right settings (on Linux this is 
/dev/video0)


QCamera * cam = new QCamera( ... );

cam->start();

When the camera is started QCameraInfo::availableCameras() returns 
list of cameras without active camera. This is a regression from pre 
5.9 Qt. Is this a known issue?


And more

QCameraInfo info( *cam );

now produces camera's info for /dev/video1 whereas cam is /dev/video0.

Is this a know issue too?

How can I workaround these issues?

Thank you.



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[Interest] QCameraInfo & Qt 5.10.1

[Igor Mironchik]

Hello.

Let's say I initialized QCamera with right settings (on Linux this is 
/dev/video0)


QCamera * cam = new QCamera( ... );

cam->start();

When the camera is started QCameraInfo::availableCameras() returns list 
of cameras without active camera. This is a regression from pre 5.9 Qt. 
Is this a known issue?


And more

QCameraInfo info( *cam );

now produces camera's info for /dev/video1 whereas cam is /dev/video0.

Is this a know issue too?

How can I workaround these issues?

Thank you.

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Re: [Interest] R: Qt3D FPS limits

[Nikos Chantziaras]

Using vsync as a frame rate limiter is not a good idea, because of 
different refresh rates between monitors. On a 144Hz monitor, you'd be 
running at 144FPS even if that's not actually wanted.


Or, you might want to run at half the refresh rate (like 30FPS on a 60Hz 
monitor.)


Vsync and frame limiting are two different, unrelated things.


On 23/03/18 10:29, Paul Lemire wrote:
Qt3D relies on your GPU vsync settings. To reach the maximum number of 
FPS, just disable vsync in your driver settings. If on the other hand 
you want to reduce FPS, call setSwapInterval on the 
QSurfaceFormat::defaultFormat and set it before starting your Qt3D 
application with QSurfaceFormat::setDefaultFormat.


Paul


On 03/21/2018 07:46 PM, Xavier Bigand wrote:
If you want to lower the limit you can simply add a pause in the 
rendering thread before the swap buffer based on a timer.
I don't really know how to do that with qt3d, but with qt quick there 
is some slot like onBeforeRendering and onAfterRendering in which you 
should be able to insert a FPS limiter.


In a general way you have to be really careful when doing such things 
because it can add some jitters in the animations if the frame-rate 
isn't constant due to a lack of precision of the timers or conflicts 
with the vsync,...



2018-03-21 17:58 GMT+01:00 Igor Mironchik >:




On 21.03.2018 19 :39, Carlo Ferraresi wrote:

Hi,
I also noticed that PFS seem limited to 60.
I would like to know if there is a way to set this threshold
since even 30 FPS are enough for my application.


Agree, and I would like to have possibility to change the limit,
and to have possibility to set the limit to infinity...



Regards,
C.


On : mercoledì 21 marzo 2018 12:02

A: Qt Project >
Oggetto: [Interest] Qt3D FPS limits

Hello,

Does Qt 3D limits FPS by 60? Or FPS is always as much as
possible?

Thank you.




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Re: [Interest] R: Qt3D FPS limits

[Paul Lemire]

Qt3D relies on your GPU vsync settings. To reach the maximum number of
FPS, just disable vsync in your driver settings. If on the other hand
you want to reduce FPS, call setSwapInterval on the
QSurfaceFormat::defaultFormat and set it before starting your Qt3D
application with QSurfaceFormat::setDefaultFormat.

Paul


On 03/21/2018 07:46 PM, Xavier Bigand wrote:
> If you want to lower the limit you can simply add a pause in the
> rendering thread before the swap buffer based on a timer.
> I don't really know how to do that with qt3d, but with qt quick there
> is some slot like onBeforeRendering and onAfterRendering in which you
> should be able to insert a FPS limiter.
>
> In a general way you have to be really careful when doing such things
> because it can add some jitters in the animations if the frame-rate
> isn't constant due to a lack of precision of the timers or conflicts
> with the vsync,...
>
>
> 2018-03-21 17:58 GMT+01:00 Igor Mironchik  >:
>
>
>
> On 21.03.2018 19 :39, Carlo Ferraresi wrote:
>
> Hi,
> I also noticed that PFS seem limited to 60.
> I would like to know if there is a way to set this threshold
> since even 30 FPS are enough for my application.
>
>
> Agree, and I would like to have possibility to change the limit,
> and to have possibility to set the limit to infinity...
>
>
>
> Regards,
> C.
>
>
> On : mercoledì 21 marzo 2018 12:02
>
> A: Qt Project  >
> Oggetto: [Interest] Qt3D FPS limits
>
> Hello,
>
> Does Qt 3D limits FPS by 60? Or FPS is always as much as
> possible?
>
> Thank you.
>
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> -- 
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>
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Re: [Interest] Efficiently render QtQuick-scene and encode to H264 on i.MX6 VPU?

[Ola Røer Thorsen]

Hi Gunnnar,

thanks a lot, this gives me a good starting point. I didn't know I could
use GL_viv_direct_texture "in reverse" like this, I'll try it out. Already
using it to stream decoded h264 video to a texture for rendering to the
screen.

I don't know which one will work best, but you want to avoid the
> QOpenGLFrameBufferObject -> QImage conversion at all cost :)
>
>
Yeah that's the one I was worried about :)

Cheers,
Ola
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