Can alpha channel from Png can be output through jit.alphablend ?

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I trie to control the alphachannel of a videoplane to make a hole, to display jit.gl.text2d.
So I did an alpha mask in png, wich I put in jit.alphablend…

But nothind occurs, everything is still black…………

Has someone experienced this ?

Thx..
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got my answer, THX Andrew as always !!!