How do I play a video and execute a function SYNCHRONIZED at the same time?

What I have:

A structure with 300 frames of a video. Each frame contains:

• 4-D matrix representing an image (the frame)
• a number
• ...(careless data)

What I need: playing this video and executing a function at the same time. This funcion would operate with this number. Let's say it would do a simple operation, but itis much complex and it must be a separated function. What I don't know to do is synchronizing the execution of the function that works whith the number with the video reproduction.

For example, the pseudocode would be:

for first_frame until last_frame
  show only frame_n
  execute function
end

And since it is a video this would be performed at 25 frames per second. Since Matlab is not good at real-time processing, i suppose the data would have to be pre-charged. No problem. I don't need real-time processing.

Aim of the main code: send data to a led bulb depending on the frame color of the video. Options I thought would be useful (but I don't know how to perform):

• calling VideoLAN VLC app I and get feedback while playing the video and, for each frame working with the video timestamp, execute the desired function.
• hit play with the mouse and a key at VLC and Matlab, what would not sync at all.

Thank you very much.