drich
Posts: 20
Joined: Tue Jul 28, 2015 7:36 pm

fullscreen video_render without linearization

Tue Jan 10, 2017 10:12 pm

Hi, is there a way a way to render a video using video_render to fullscreen without linearizing it ? I would like to get an output as sharp as possible.

6by9
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Re: fullscreen video_render without linearization

Wed Jan 11, 2017 11:15 am

What form of linearization are you referring too? A gamma curve on rendering for colour space adjustment/display compensation?

AFAIK The gamma curve is left straight as there are so many different HDMI displays that could be plugged in, and each will have subtly different characteristics.

If rendering a YUV image, then as HDMI is normally driven as RGB there is a colourspace conversion. video_render does support selection of various colour conversion matrices (see OMX_COLORSPACETYPE for use with OMX_IndexParamColorSpace)

The image will be resized to fill the screen if necessary. If the source image is the same size as the display then it should be a 1:1 pixel mapping and no resizing filter used. If they differ then it'll use a filter.
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drich
Posts: 20
Joined: Tue Jul 28, 2015 7:36 pm

Re: fullscreen video_render without linearization

Wed Jan 11, 2017 1:59 pm

Ah, sorry I expressed badly, I was actually asking about the pixel ratio when the video resolution is smaller than screen resolution.

I just tried to use egl_render to show the texture using GL_NEAREST parameter, but it looks like there is still linear smoothing (I think there should be a visible difference with the 1024x576 resolution I'm using), maybe I'm missing something

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
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Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: fullscreen video_render without linearization

Wed Jan 11, 2017 3:20 pm

In which case I don't think there is any exposed control over it. Resizing just using nearest neighbour is going to look pretty horrid.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
Please don't send PMs asking for support - use the forum.
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dom
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Re: fullscreen video_render without linearization

Wed Jan 11, 2017 5:00 pm

It is possible to force nearest neighbour scaling through dispmanx resizing (used by video_render). See: here.
But I'm still unsure if that is what you are asking for.

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