Ask HN: Can I make a video not downloadable?

Play it in a private movie theater and search everyone for video equipment, and make sure no one besides yourself or trusted associates are allowed to handle the film. And don't make copies of it besides backups locked up in safes.

If it can be displayed in any way to a human eyeball, then it can be copied.

The question is what kinds of copying are you concerned about, and how hard are you willing to work to make that difficult?

No.

I heard about DRM.. is it secure ?? or it can be byassed.

It is reasonably secure against ordinary people. Against technically sophisticated approaches it is likely to be bypassed as "just another day at work." Easy to implement DRM might be worth the time spent, on the other hand, making something that people care enough to pay for and therefore avoid paying for by bypassing DRM is really the important problem.