Video In? That's pretty much very hardware specific stuff there. I doubt there's any allegro functions that actually read what's coming through a video-in port, much less do anything with it. Check the manuals, there's probably nothing in there. Most likely you'll need to figure out how to access your video card directly through the operating system, or whatever. I don't know much about accessing hardware.

Also, you need to include more information about your question than "State Question (simply) then Request Code". What are you going to DO with the video in? Do you want it to show to the monitor, or do you want to just do stuff with the content feeding in in the background - like dump it to an avi file without it rendering anything to the screen? More information always helps, and will make people more willing to help you out.

if you simply mean putting video in your project then MJPEGAlleg should do it for you, it's not quite MPEG, but you can take an AVI and use it just fine in an allegro application.. the sound quality still is lacking though from last I heard.

i mean composite video signal from say a camera or VCR.. pluged into a video input card in PC.
then i get a "surface" of some sort with the signal on it, that i can use in my app, which happens to use alot of allegro.

i think virtual dub has code for captuing direct to disk, which by-passes the "surface" that i would need to access.

i think i needs direct show code.

Two steps to go here:
1) Capture the video input to an OS-native surface/bitmap
2) Transform to allegro.

1) Depends hugely on your platform; looks like you're using windows, and you sort of half-solved the problem there (if not, I can't help you. Find a good lib).
2) Is comparatively easy. Check the allegro docs about how to convert a windows HBITMAP to an allegro BITMAP. No idea about other platforms, but I'm pretty sure if it's not DOS, it should be doable.

Now I'm learning Direct Show. There are good examples. I thing there's some example about video capturing. Copy&paste the example and made the proper changes (that's basically what I did with MVPlayer).

What you must do is programming a filter that converts uncompressed video to an allegro bitmap, and connect it to the filter graph, removing first the filter that renders the video to the screen or saves it to a file. I can't help you more at the moment.