In this paper, we propose a switching scheme of GCR Block Ack and GCR Unsolicited Retry, standardized in IEEE 802.11aa, according to network conditions for video and audio groupcast over wireless LANs. We utilize three transmission modes in the proposed method: GCR Block Ack with four retries, GCR Block Ack with two retries, and GCR Unsolicited Retry with twice transmission. The proposed method is compared with the three individual methods by computer simulation under various network conditions to evaluate application-level QoS. We then assess QoE by a subjective experiment. We show that the proposed method can choose an appropriate mode and achieve better QoE than the individual methods.