AVCHD Merger

AVCHD Merger is a tool designed to join video clips of different formats into a single file with the .m2ts extension. It offers support for .m2ts, .ts, .mov, .mp4, .3gp, .mpg, .avi, .wmv and .asf files for the input.

Combine multiple videos into one

After a brief setup procedure that shouldn't give you any trouble, you're greeted by a user-friendly interface made from a normal window with a clear-cut structure.
You can add as many video files to the task list as you want, preview them in a small built-in media player, as well as proceed with the merging operation by specifying the saving directory and name of the new file.

Modify default AVCHD settings

If you're not satisfied with the predefined AVCHD profile, it's possible to make adjustments related to the video bit rate, frame rate, size and scale, along with the audio bit rate and sample rate.
A custom size may be applied as low or high quality, bi-linear, bicubic, nearest neighbor, or high quality bilinear. As far as the stretching mode is concerned, the video can be stretched to fit. Otherwise, you can instruct AVCHD Merger to keep the aspect ratio, resize without the letter box, or don't resize at all.

Evaluation and observations

It took a while to carry out merging operations in our tests, during which it remained light on system resources, thanks to the fact that it needed low CPU and RAM to work properly. No error dialogs popped up and it didn't hang or crash.
Worth mentioning is that it's capable of merging multiple files of various formats and sizes. However, the application doesn't excel when it comes to maintaining the image quality.

Conclusion

All in all, AVCHD Merger comes equipped with straightforward options for combining multiple files with different video content into a single .m2ts clip.