How to use GstVideoAffineTransformationMeta in gstglimagesink

[Grégoire Gentil]

Hello,

I'm interested to use GstVideoAffineTransformationMeta in 
gstglimagesink, especially in gst_glimage_sink_on_draw:

https://cgit.freedesktop.org/gstreamer/gst-plugins-bad/tree/ext/gl/gstglimagesink.c#n2028

I have a pad probe installed in my pipeline in which I do:

static GstPadProbeReturn cb_have_data(GstPad *pad, GstPadProbeInfo 
*info, CustomData *data) {

GstBuffer *buffer = gst_pad_probe_info_get_buffer (info);

GstVideoAffineTransformationMeta *meta = 
gst_buffer_add_video_affine_transformation_meta (buffer);

//To be modified
const gfloat matrix[16] = {
0.1f, 0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f,
};

gst_video_affine_transformation_meta_apply_matrix (meta, matrix);


But when the code reaches gst_glimage_sink_on_draw, af_meta =
gst_buffer_get_video_affine_transformation_meta 
(gl_sink->stored_buffer[0]); is NULL.

Any idea how I could use GstVideoAffineTransformationMeta to have my own 
transform matrix?

Thanks in advance,

Grégoire