Since the very beginning, the AVCHD specification had supported 720-line progressive recording mode at frame rates of 24 and 60 frames/s for 60 Hz models and 50 frames/s for 50 Hz models. Frame rates of 25 frames/s and 30 frames/s are not directly available in 720p mode, but can be simulated with frame repeating, when every frame is either repeated twice or a special flag in the video stream instructs a decoder to play every frame twice to adhere to output rate of 50 or 60 frames/s.