converting videocrop to use VideoCropMeta

[Stirling Westrup]

On Mon, Mar 3, 2014 at 12:21 PM, Nicolas Dufresne <
nicolas.dufresne at collabora.com> wrote:

>  Le lundi 03 mars 2014 à 11:37 -0500, Stirling Westrup a écrit :
>
>  Just wanted to mention that I keep looking at the GstVideoCropMeta for my
> cropping needs, and its insufficient. Basically, it assumes that the crop
> area is entirely contained within the frame. I have cases where I want to
> 'crop' a 1920x1080 frame with a 1920x1080 rectangle starting at y
> coordinate -960, so as to have just the top half of the original frame in
> the output frame. videobox can do this, but videocrop cannot, and I fear
> the author of the GstVideoCropMeta feature didn't consider that use case,
> as starting coordinates must always be positive.
>
>
> Well cropping API will just crop, it's not a video placement API. Placing
> the video on screen is handled through
> gst_video_overlay_set_render_rectangle(). If you have a post production use
> case, then you can use videomixer pad properties, or videobox. If you need
> to create pixels that don't exist (e.g. black borders), you are no longer
> just cropping. GstVideoCropMeta was specially designed to offload decoder
> related cropping (where left and top cropping can be positive) operation to
> the video sink, instead of having to make a copy. Otherwise, the video
> would always be cropped from right and bottom, as this is implicit in all
> color format we support.
>
>
I understand. I figured it was likely a case of GstVideoCropMeta being
intended for other uses than mine. I guess I shall have to look into
writing some sort of 'AreaOfInterestMeta' for the kind of things I'll be
doing, unless videomixer has features I need. I must admit I didn't know it
even existed until now.

For what its worth, I'm doing video-wall work, where each of 4, 9, or 16
monitors shows one cropped area each of a video stream. Naturally, if I
could just mark areas to show in the input video, and have each sink grab
its own area of interest, then I wouldn't need to have 16 streams which get
individually cropped and border-added.


-- 
Stirling Westrup
Programmer, Entrepreneur.
https://www.linkedin.com/e/fpf/77228
http://www.linkedin.com/in/swestrup
http://technaut.livejournal.com
http://sourceforge.net/users/stirlingwestrup
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