Current network services such as Voice over IP or IP Television pose new challenges to network providers. Network operators need to know if their services are being properly provided. However, current quality of service parameters commonly used in data networks (e.g. throughput, packet delays, packet losses, etc.) do not show a clear view of what the users are experiencing. Thus, it is necessary to translate such measured quality parameters into a quality of experience value. Several models are being developed to cope with this problem. For instance, some approaches have used the packet loss rate to evaluate the experienced quality of an IP television channel. Unfortunately, packet loss just explains a fraction of the quality behavior. Then, we go one step further, taking into account the different MPEG frame types that are transmitted. In this paper, we have defined a model to predict the experienced quality that is a function of the loss of the different types of MPEG frames, providing a mean opinion score of the delivered service. The final results show that our model is able to better predict the quality of experience of such video services than just using the packet loss rate.