1) The output video resolution is incorrect.
A video's resolution is its size in pixels, horizontally and vertically.
It is usually listed as the width times height: 1920x1080, or just the height: 1080p. This means that the video is 1920 pixels long and 1080 pixels high.
The higher a video's resolution, and the more pixels it has, the more detail it can preserve.
If your output video is worse than the original, it may be the case that the resolution was selected incorrectly.
You can check the original file's resolution. To do that, check the video information next to the file's preview:
When you choose the output resolution, select the same resolution to preserve the original quality, or choose a lower resolution to reduce the file size.
If you cannot find a suitable preset, you can select the necessary properties manually.
Click the cogwheel button next to the format box to modify the video and audio properties of the currently selected preset.
2) If the output resolution is the same as the input, please check the bitrate you select for the output file.
Bitrate is, essentially, the amount of information used to encode one second of video (or audio).
The higher bitrate you choose, the larger files of better quality you get.
Please note that it is not possible to increase the quality above the level of input file, but you can only retain the same video quality at most.
3) Sometimes the video is affected by the outdated graphic card drivers during the conversion.
Please check these instructions to update the drivers.
4) Check the converted file playback using the original Movavi Video Converter.
If your file playback is fine in the video converter's player, consider using a different media player or install the KLite codec pack that would help you to play your videos with a player of your choice.
5) Your media file is converted for a device, but it does not look well on your device.
Please check the specifications for your device using the device manual and try customizing the preset in Movavi Video Converter.