Re: Python access to video frames

Hey,

I figure the most elegant solution here would be for you to implement
this as a GstVideoFilter[1] subclass. 

You would implement transform_frame_ip to both store older, "correct"
images, then write into the incorrect images as needed.

You might encounter issues with the bindings / annotations however, I
have only implemented BaseTransform subclasses personally[2].

Good luck!

[1]:
https://gstreamer.freedesktop.org/documentation/video/gstvideofilter.html?gi-language=c

[2]:
http://mathieuduponchelle.github.io/2018-02-15-Python-Elements-2.html

On Thu, 2023-10-12 at 19:03 -0500, Carl Karsten via gstreamer-devel
wrote:
> I need to alter video frames, and Python is my happy place.
> my gst skills need some help.
> 
> I think I need these 2 things:
> 
> 1. pipeline:
> read a file,
> decode the video,
> hook? to read/write pixels,
> encode (keep the original audio)
> save to disk.
> 
> 2. that hook code...
> I have done something before: use the wavelevel element to get audio
> data and generate static png images.
> https://github.com/CarlFK/veyepar/blob/master/dj/lib/gslevels.py#L72
> 
> So I am assuming some element / message will give me a frame buffer
> thing of data, and somehow i can detect black pixels.
> 
> 
> End goal: fix some video;s I made of a live event where my setup
> introduced black squares - I want to replace the black with the
> pixels
> from the previous frame.
> example of what needs fixing:
> https://youtu.be/N5Anbq8vYNk?si=Gl89X3Uk5_2CrMu6&t=148
> 
> The slide is mostly a static image, so the previous frame will be
> fine.
>