Has your university given you a scholarship? If you have a full scholarship, then there is no need to open a blocked account or even show a bank statement. If you are on a part scholarship then you need to show the remainder of the money in your blocked account. For instance, if your scholarship provides you with 400 euros every month, then you need to show 3,840 euros in your blocked account.
Which country are you from? If you are not on a scholarship, then most German embassies do not accept only a bank statement from a sponsor in your home country. You either have to open a blocked account in Germany or provide a sponsorship letter from someone in Germany who is financially stable. If you have a scholarship, it's a different story.