Fast lightweight encryption algorithms must be developed to satisfy the level of security and the real time constraints. However the recently proposed lightweight MPEG video encryption algorithms that have been proposed in the past suffer from certain drawbacks. While some of them require hardware support, the others are weak or reduce the MPEG compression ratio. The lightweight encryption algorithm called VEA is fast, satisfies the real time constraint and does not reduce the MPEG compression ratio. However, it relies on the key generator to generate a good encryption key and it cannot withstand the known-plaintext attack. In this paper, improvements to the VEA are proposed namely the Rotation algorithm, the XOR algorithm and one that combines VEA with IDEA (I-VEA). They are able to secure MPEG video with minimal computational overhead, which do not reduce the MPEG compression ratio, do not rely upon the key generator to generate an effective key and can better resist the known-plaintext attack. The Rotation algorithm is the fastest of the three, but is relatively weak. I-VEA is the most secure but it adds the maximum computational overhead. The XOR algorithm is a good compromise between the two.