Gets private data set on the picture via gst_h264_picture_set_user_data() previously.
Update reference picture type of picture with reference
a GstH264PictureReference
%TRUE if reference needs to be applied to the other field if any
Sets user_data on the picture and the #GDestroyNotify that will be called when
the picture is freed.
If a user_data was previously set, then the previous set notify will be called
before the user_data is replaced.
a #GDestroyNotify
Create new #GstH264Picture
Create new #GstH264Picture