Any way to do that? I need to make the background of my video transparent but the code read the transparency as black (under of my video is another video).
Which operating system are you using? This may not currently be possible with the default video players (although you may have some ability to set up a custom GST pipeline in Linux). As an alternative, you could convert your video frames (with transparency) to an image sequence and play them manually … but there are also addons for playing image sequences (e.g. https://github.com/bakercp/ofxPlayer).