Question: I am looking for a solution to control my computer mouse just with my hands and a webcam. The goal is to combine it with voice input to let me move more freely in front of my desk.

It should support the usual mouse actions:

* position mouse pointer, left click, right click, middle click, scroll up, scroll down
* optionally: scroll left, scroll right

Answer: 
Use [ffmpeg](http://ffmpeg.org)

```
ffmpeg -f concat -i mylist.txt -c copy output.mkv

```

Put path to your MKVs in mylist.txt in line seperated manner. You don't even need to think about re-encoding. The codecs will be copied as-is. Quality unchanged.
[avidemux](https://en.wikipedia.org/wiki/Avidemux) can add .mkv files at the end of each other.

Usage: Open the avidemux GUI, drag-and-drop the first .mkv file, then the second, then press "save" and enter the filename you want for the output file.

The input files must have the same size and encoding.

Available for Linux, Mac, Windows.

It is free and open source. It uses ffmpeg's libavcodec library under the hood.