Audio speed is faster than video

Ripped DVDs or converted .avi files audio speed is faster than video when played on iTunes but not if played on Apple TV. Theses files worked fine prior to the newest version on iTunes but not they audio speeds up as the video plays. If you pause the video, and play it again the audio is synchronized with the video. But as the video plays the audio is still faster. If I play these same files on mu Apple TVs the audio and video are perfectly synchronized. Any ideas?