A common issue with most media players is that their preview function cannot accurately determine the duration of variable bit rate (VBR) files in advance. Until the file is played and its actual duration is known, players typically estimate the length based on the file size and the bitrate of the first MP3 frame. For a more precise duration display, the file would need to be fully scanned, which takes considerable time—something most players avoid.

This issue does not occur with files exported at a constant bit rate (CBR). However, CBR files tend to be slightly larger while maintaining comparable quality.