P2P TV distribution is going commercial, and the video quality delivered to users becomes of the utmost importance. However, the impact of P2P distribution on the video quality is not completely understood yet, especially in live streaming situations. This work addresses the impact of P2P distribution when the delay of the playout is limited, as it must be in any true live TV service. A methodology for the evaluation (using standard objective video quality metrics) is proposed, showing that different ways of grouping frames in chunks for the distribution can lead to very different quality when the system is overloaded.