Fluctuations of video quality over time can have a significant influence on the overall perceived quality as represented by the QoE. Existing methodologies for subjective video quality assessment, however, are often not suitable for the evaluation of these quality fluctuations, especially if they occur within very small time frames. In this contribution, we therefore propose a new method, VIQPAC, which addresses this shortcoming by using a pattern categorisation approach. Instead of requiring the subjects to provide a continuous quality evaluation, the subjects assess the overall quality impression and the strength of the quality fluctuation, combined with a categorisation of the encountered fluctuation pattern. This allows us to determine the fluctuation dependent temporal changes in the quality. The results show that VIQPAC is able to capture the pattern and strength of quality fluctuations, allowing for a proper description of the temporal quality changes within a video sequence.