Lips not in sycnh with voice in recording using Debut

[sabathiel]

I am using Debut Video recording software version 1.63 free edition. My computer is a quad core Intel CPU but I am having problem recording videos in HD using my Logitech C910 Full HD webcam. I am only recording in 720p mode not 1080p mode. I am recording me singing using instrumental backing tracks with an external studio recording mic connected to a mixer which is connected to the line in input of the computer sound card. I have tried various file formats but some of them are very choppy just watching my movements on the scree let alone pressing the record button. The best format is AVI with MPEG2 codec and I can see my movements on the computer flowing nicely. But the problem with it is that the final result of the recording after watching the video file for awhile the words coming from my out is not in synch with the voice on the video by a second or half a second maybe. I have no problem when using the Logictech Webcam software but that program can only record in mono when using an external mic and not using the webcam mic. I tried playing around with the various settings like the average and max bit rate or the frames per second but the problem remains.