Java VLCJ canvas and drawing ontop with transparent background

Question

I have spent a bit of time researching about whether it is possible to draw on top of a VLCJ movie within a Java application. I have found a few bits of conflicting advice some saying it is not possible and some referencing articles which have moved on oracle.com.

Can someone clarify if it is or is not possible to draw java2d graphics like rectangles/lines which also have transparent backgrounds so the video stream underneath can be viewed whilst the shapes are present on screen?

If this is not possible with vlcj what would be a good alternative for a linux and windows compatible media player allowing for annotation over a playing video stream? Please note i do not have to be limited to java but something where i can get re-use out of developed drawing routines for multiple platforms would be ideal.

Answer 1

Yes, you can do it. For the normal hardware rendered video player, you need to have at least Java 6u10 (preferably 7) and achieve this by overlaying a transparent JWindow on top of the VLC canvas (it's not too hard to add events to the canvas to check for updates in position / size and then move the overlayed window correspondingly.)

The other way that doesn't involve using overlaid windows is to use a DirectMediaPlayer, where you have access to the framebuffer directly (and can therefore do what you like with the pixels, including wrapping them as textures round 3D objects and so on.) So with this approach, you could simply draw what you wanted onto the frame buffer before rendering it to screen in the way you chose. This is the most flexible approach, but comes with the downside that if you're not very careful about your implementation, you lose all the GPU acceleration and end up crippling the CPU, especially for HD video.

If a simple overlay would do the trick, I'd try that first, and just resort to a DirectMediaPlayer if you have to.