AirPlay sync on Apple TV

I have a video on my MacBook Pro. It plays in sync when I play it in QuickTime or VLC. If I AirPlay the video to Apple TV and set the MBP screen to mirror, and the audio to play from Apple TV, the sound is wildly out of sync. I press play on the MBP and the video starts immediately, but the audio doesn't. About a second later the audio starts and of course it's now way out of sync. If I throw the video to the Apple TV, but leave the audio output on the laptop speakers, the audio is in sync (or close it) with the video on the Apple TV. I press play and the video starts on the TV, and the audio simultaneously plays from the Mac.

Clearly this is not the way the system is intended to be used. Can any one tell me what I'm doing wrong?

Thanks very much.