You have the option to transcode uploaded videos using the 2-pass method with VIMP. Videos transcoded in this way usually have a better quality than videos transcoded in the 1-pass process with the same file size.
Technically, transcoding in the 2-pass process is performed in two passes. The first pass analyzes the video and the second pass transcodes it based on the data obtained in the first pass.
You can activate 2-pass encoding under:
Configuration -> Transcoding -> Transcoding OpenSource -> Use Two-Pass Transcoding
The duration for transcoding the defined formats approximately doubles when 2-pass encoding is enabled.
2-pass encoding can be enabled for each format individually (for the default format in the configuration, for the additional formats under Media -> Formats).
Ideally set a maximum video bitrate per format to limit file size.
2-pass encoding automatically uses VBR (Variable Bitrate), even if the bitrate setting is CBR.