The video footage circulating the internet of "Pit Dernitz" being attacked by lions is fake. This thread at snopes (http://message.snopes.com/showthread.php?t=13428 ) contains many arguments why. If you carefully watch the video you will be able to verify most of them quite easily.
For my part, the most obvious reason why this is fake is the reaction of the people involved (including the cameramen). If you were in a car and saw someone else being attacked, would you pan away to film the reaction of his family watching? If your husband climbed out of a car and got attacked by a lion, would you really do nothing? Nobody tried to run into the lions with a car.
The claim that the terrain didn't allow the people to use the cars to scare off the lions is total nonsense. The sequence showing the man walking from the car to the lions makes it obvious the terrain isn't very rough at all and there are (at least in front of the car that he got out of) no major obstacles that would prevent the car from being used to move close to the lions.
Wild lions (especially in a game park in Namibia or Angola in the mid-70s) would not be this tame. The lions are extremely close to the cars suggesting they are tame or at least very used to cars, something that is exceptionally unlikely for a Angola/Namibia game park even today nevermind in the mid-70s.
When a wild lion attacks prey, they don't push the prey around and nibble at limbs. They attack to kill. Usually breaking the neck and/or severing the aorta. For a prey this weak this would happen in a split second, not several minutes. The way these lions behave with the man suggests they are playing and not attacking.
The whole seen is set up as tourists coming across lions in a wildlife park with some video recording equipment, but the quality of the video is way to good for simple amateur footage in the mid-70s.
There is way too little blood in the whole scene to be real. The blood patterns are also not nearly random enough. I recall a scene where both the victim's thigh's are visible, each with one neat stripe of blood straight down the middle of the thigh. Too "neat" to be real. Also, the blood pattern suggests blood had been flowing down the thigh from the top (i.e. implying a wound bleeding while in a standing position), but there appears to be no wound that would cause blood to be there inflicted on the man while he's in a standing position.
The conflicting reports about the location suggest that this was in a wildlife park somewhere near the Angola-Namibia border (some reports say it was in Angola and some say it was in Namibia). The vegetation seems to be consistent with this area as well. However, in 1975 there was a war on this very border (the South African Border War (see http://en.wikipedia.org/wiki/South_African_Border_War). This was a particularly savage ground war fought over the Angola-Namibia (then South West Africa) border from 1966 to 1989. I don't think too many Belgian tourists would have paid a visit.
It's unlikely this was elsewhere in Angola as parks higher North have a more tropical climate and most of the rest of Namibia is desert climate (i.e. both inconsistent with the type of vegetation shown in the video).
There doesn't seem to be any official answer, but on the balance of all the inconsistencies, it's pretty clear that this is a fake.