I have prepared a powerpoint presentation of 20 minutes and 43 seconds. When I am converting it into a video, the time is getting reduced as per the quality of conversion, i.e.for,:-
960 x 720 - 20 minutes and 06 seconds
640 x 480 - 20 minutes and 29 seconds
320 x 240 - 20 minutes and 40 seconds

The video conversion as per the last quality mentioned is fine but the quality is very low to be presented.

The problem in the rest 2 quality variants is that the images in the presentation are displaying in less time as designed as a result of which the audio attached remains incomplete.

Please help!!!