1Video Mixer 2----------- 3 4A generice video mixer, it blends the ayuv buffers from all pads onto 5a new buffer. The new buffer has by default a checkerboard pattern but 6its color can be changed with a property. 7The mixer can mix streams with different framerates and video sizes. It 8uses the duration value of the buffer to schedule the rendering of the 9buffers. For streams with a different resoltion than the final output 10resolution one can specify the position of the top left corner where this 11image should be placed with the pad properties xpos and ypos. 12The overall alpha value of a stream can also be specified with a pad 13property. 14By default, the streams are blended in the order that the pads were 15requested from the element. This can be overridden by changing the 16zorder pad property of the stream, a stream with lower zorder gets 17drawn first. 18 19 20TODO 21---- 22 23- really implement zorder 24- take I420 yuv as well 25- output AYUV if possible. 26- implement different blend modes, some code is already done 27- use filter caps on srcpad to decide on the final output size 28