The purpose of video encryption is to protect video content, which can usually be achieved by using digital rights protection (DRM) technology. There are many ways to crack this kind of encrypted video, but they are either illegal or very complicated, and the effect may not be as expected.

Generally speaking, the cracking methods that can be adopted are:

1. brute force cracking: This is the most undesirable cracking method, and it will try to crack the DRM protection mechanism by exhausting all possible passwords.

2. Cracking the key: This method can crack the DRM protection mechanism, but it takes a lot of time and energy.

3. Exploiting vulnerabilities: This method needs to study DRM protection mechanism and exploit vulnerabilities to crack it.

4. Purchase decryption service: This method allows users to crack the DRM protection mechanism by purchasing decryption service.

In a word, it takes a lot of time, energy and money to crack encrypted video to get satisfactory results.