Focus Video is a very convenient and user-friendly video compression and format conversion tool, supporting common audio and video formats such as MP4, MOV, WMV, MKV, AVI, WEBM, MPG, 3GP, FLV, TS, FLAC, APE, and Mp3.

The "Video Compressor" of Focus Video offers four video compression modes, including compressing by ratio, by file size, by video quality, and by video bitrate, with the default mode being by video quality.

Compressing by video quality refers to the commonly known Constant Rate Factor (CRF) compression method. This method is often used by subtitling groups during video encoding because it effectively balances video quality and file size, ensuring that video quality is maintained while minimizing file size.

The video quality mode supports adjustments to the quality parameters, CRF, and the preset. The default value for the quality parameter is 23, with recommended values ranging from 18 to 28. A higher quality parameter value results in a smaller output file size, albeit with a relatively lower video quality. If high video quality is required, the CRF value can be set within the range of 18 to 23, with 18 theoretically achieving visually lossless compression.

You can follow the steps below to start video compression:

1. Click the select video files button, or directly drag the video file or folders into the main window of Video Compressor. After importing the video files, click the "Change options" button to enter the compression options window.

1. In the Options window, you can see that the default compression mode is By video quality. And you can modify the CRF and Preset parameters there.

1. Once all the files have been imported, and options been settled, you can click the start button at bottom right to start all tasks.