Audio Problem with VS X4 Pro: Dolby 5.1 converts to stereo

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I tried several searches for my topic, but none of the results were on my issue. I'm hoping someone could advise me on this problem.

I have recently started using a new video capture device (a KWorld USB TV Tuner with recording capability). I have recorded a program off a local HD broadcast channel. Here are the specs of the original video file:

VIDEO: MPEG-2 format, File size 6.91 Gb, Duration 1:05:40, 29.97 frames per second

AUDIO: Type Dolby Digital Audio 5.1, Attributes 48000 Hz, 5.1 channels, Bit Rate 384 Kbps

I have used few different versions of VideoStudio in the past and am currently using Corel VideoStudio X4 Pro. When I use a video capture device to record video, then use VS to edit it, I then save it by clicking SHARE, then CREATE Video File, then SAME as First Video Clip. Everything works just fine. So, I used the same procedure to save (render) this HD video and the video turned out just fine, but the audio was much softer in volume than the original. I checked the audio specs of the newly rendered file and found the following:

AUDIO (of new file): MPEG audio layer 2, 48 Khz, stereo

I don't know why VS changed the audio from Dolby Digital Audio 5.1 to MPEG-2 stereo. I retried this after clicking on SETTINGS and checking to Enable 5.1 Surround, but the same results happened. I checked my owner's manual, but I didn't find anything that pertained to this issue.

Does anyone know how to edit HD video with Dolby Digital Audio 5.1 then save (render) and retain the original Dolby Digital Audio 5.1 ?? Is is possible with VS X4 Pro, or would I need a more recent version?

Thanks for any help!