BOX4

Aiming to help you convert videos from one format to another in the simplest manner possible, BOX4 is a video re-packager with support for MKV and MP4 containers as output.

Clean GUI and support for multiple containers

No installation is required, so you will be able to enjoy BOX4 as soon as you double click on the executable file. Its interface is simple, modern-looking and neatly organized, allowing you to open an entire folder of videos, or select individual files to process in batch mode. As such, you can use it to convert multiple files in one go.
BOX4 is compatible with multiple file formats, namely MKV, MP4, MOV, TS, and FLV. In other words, you can use it to convert MOV, TS, and FLV files, convert between MKV and MP4, or modify the settings of MKV and MP4 containers.

Change the audio settings before conversion

For each input file, BOX4 displays the name and the location of the original file and the resulting one. By default, the output is saved to the Videos directory of Windows, and there is no option to change this.
Once you choose the output, you can proceed and customize the audio track settings. BOX4 enables you to choose the audio codec (AAC, MP3, or copy the original) and change the audio bitrate.

Video encoder that needs further work

BOX4 features a clean layout, but when accessing a specific section (such as Profiles or Settings), the buttons bar is disabled, and a 'Return' button is displayed. You cannot access any other section of the app before pressing this 'back' button, which might be a bit annoying.
BOX4 features fast conversion speed and a slick look, but that is certainly not enough. It needs further improvements to appeal to potential users. Furthermore, unlike other applications in its category, the file types it supports is quite limited.