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Old 10-23-2008, 11:22 AM   #1
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Superimposing a bitmap on top of a live video stream

Hi everybody,
if OT, please point me to the right thread.

Briefly, I'm involved in a long run project which hunts for the following goal: one cheap general purpose x86 mother board with solid state storage media; a small Linux distro with X-window but without a desktop manager like GNOME or KDE; the ability to show an Ogg Theora encoded video stream; the ability to freeze the real time stream at a given frame and then superimpose some small bitmaps. Period.
I can code in C or other "close-enough-to-the-hardware" languages.
How could I face such a challenge in a consistent, possibly well defined, manner?

Old 10-24-2008, 07:59 PM   #2
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Video players shouldn't need Gnome or KDE. Superimposing graphics on a live stream sounds like a video switcher application. ( like Trinity, Video toaster, etc.) One of the ImageMagick programs can superimpose a graphic on a picture. Perhaps mplayer could save a snapshot at a certain point and ImageMagick could add the graphic. However, I don't think this would be instant. I'm not certain from your description if you just want this on the screen or if you want the result on it's own stream or saved to a file.

Read though the mplayer documentation. It may be able to do this. Look at the documentation for the gstreamer and MLT frameworks if you will need to roll your own application.
Old 10-25-2008, 05:43 AM   #3
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Thanks jschiwal,

I don't need to save the result. My goal is to show some color graphics on top of a still background which comes from a video stream.
Imagine the inside working of a slot machine. At first, you see a still image of the three wheels, let's say an orange, a lemon and an apple.
When a player puts in a coin and gives the start signal, you see a live motion picture of the spinning wheels. After a random delay of few seconds, the movie freezes and shows a still image of two lemons and one apple. Please note that I'm NOT describing my real application. This is just an example. When the movie freezes, I have to superimpose some simple animated graphics on top of the wheels. For example, I could faint the apple from glow red to dark green, or squeeze the lemon. In case of a triple match (jackpot), I could turn the three apples to one big apple pie with a flashing 100 or 134 or 2612 or whatever else is the running score. I'm tempted to simply "hardwire" as still image each and every possible score, but I feel more viable to take a snapshot of ten single digits from 0 to 9, then arrange them in real time on top of a still background.
If possible, I would like to code one single executable which manages to read from some regular files, and painlessly write in real time to some virtual resource which represents the visible surface of the screen.


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