99% of the time he is not 'whipping' her anyway .... The only saving grace is that what he is using is all noise with no effect ... I've produced commercial BDSM/Spanking videos for decades, so I can recognise what is actually 'real' ... Very little is and this certainly isn't.
Looks to me like the Slave Owner is hitting his girl on her lower back. Upper back & buttocks only guys! He may injure her organs. Then she would sicken & die!