Uploading Video to a Share Pod: Best Practices

Can anyone offer insight on best practices when uploading a video to the

share pod? I understand that the maximum file size is a bit over 100MB but

there does seem to be other issues that can affect playback. I uploaded a

65MB SD video that plays back fine on all devices but playback of a 10MB

HD video and the audio lags. Why? Clearly file size isn't the problem

here, but why does a much smaller HD video cause audio lag when a large SD

video doesn't?