Why two clicks while in Live View (LV)

I have 5100.
When I have the camera in TTL view finder mode and click the shutter it clicks once and the picture is taken.
However when the camera is in LV mode (single servo) the shutter seems to take two pictures, by the sound of it. It does only take one picture, when I look at them, but it seems to be a lot of noise and the sound is exactly the same for both actions.
To test this out for yourself put your camer in LV Auto (although it seems to do this in all modes) Now take a picture. The sound is exactly the same the first time it clicks and the second time it clicks. It seems to be taking two pictures.

However in testing, if I at the first click take a picture of one scene and then quickly move the camera to a second scene it is only the first scene that shows up.
Perhaps I have some setting that is set that I dont remember, or is this normal for everyone.

Confused ..
Thanks.

First click is the camera taking the photo. The second click is the mirror popping back up to return to Live View. If you listen, you'll hear the same click (the mirror) when you first enter Live View since the mirror needs to be up. A little confusing the first time you hear it, but once you know what it is...

Thanks for your answer.

Ok this may be a long discussion. Because there seems to be a lot of talk about the mirror in LV and what happens to it when taking a picture.

It is my understanding that the mirror in live view is up and that it stays up. That it does not come down during the process. Thats why the eye piece does not work in LV. Some say that the way to keep the mirror up if you want to stop vibration is indeed to put it in LV single servo and this keeps it up.
Also try this experiment. Put your camera in LV then do One of these two things.

1. Let the camera sit unill the LV turns off, times out. You will hear the mirror go back down. from being kept up, I believe. So the mirrors is up in LV from what I can tell.

2. Turn on camera, turn on LV now remove the lens with the camera on. You will hear the mirror coming down, its very distinctive.

If you look at a utube video Nikon D3100 Mirror Lock up trick - YouTube
This person has a 3100 but shows that in LV that the mirror stays up.

It is my understanding that in live view the mirror has to be up because its now using the Sensor like a live camera and then displaying it on the monitor on the rear of the camera.

I think if you look down the lense with the lens on you can even see the difference between when the mirror is up and down. I think the mirror stays up all the time.

I am no expert but these appear to be my observations.

What are your thoughts on these comments.

Regards

All I can add is that I remember reading that every shot in live view counts as 2 shutter releases since there's dual mirror action going on, or something along those lines.

I think during live view the shutter would be wide open. When you take a picture, it needs to shut first to prepare, then open and shut for the specified exposure time, and finally reopen again to go back to live view. I think...

Well I typed a response but then it wanted me to log back in and it seems to have lost my post, so I will re post. Hopefully it will not post my old post that is the same content as this one.

Your response below, may be the right answer. It certainly makes sense. I suppose the apeture needs to be wide open to view the subject then it needs to close down to take the right photo then open back up ready for you to look through the LV again. Although now some might want to rethink the thought that LV is less shaky. It seems to be more going on than in eyepiece mode. We will see if others have comments on this.
Thanks.

nickt said:

I think during live view the shutter would be wide open. When you take a picture, it needs to shut first to prepare, then open and shut for the specified exposure time, and finally reopen again to go back to live view. I think...

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