XMMS, the X MultiMedia System, is a popular media file player which can play MP3 files, among many other formats. The XMMS package, built by the Gentoo Portage distribution system is not built properly. The problem with the Portage-built XMMS player is file seeking and the displayed playback time do not work properly with CBR encoded MP3 files. However, playing the same MP3 files with XMMS build from the source code tarball has no such problem. The tarball is built using the GNU automake configure script. This build problem was found with XMMS version 1.2.10-r15, but is known to also exist in version 1.2.7-r19.

Bugzilla Bug 118956 in the Gentoo Bug Tracker references this issue. Apparently Vorbis-OGG audio files also have some of the same playback problems as with MP3 files. The exact problems with the Portage-built XMMS are explained well in this incident report.

This problem was brought to the attention of mpgedit by a Gentoo user, who thought it was mpgedit that was somehow corrupting the MP3 files, resulting in the incorrect XMMS seeking and playback problems. However, mpgedit development uses XMMS daily and uses this player as a verifier for files edited with mpgedit, especially variable bitrate (VBR) encoded MP3 files, which will exhibit similar issues when the Xing header prefix is missing or is incorrect. Given the frequent use and testing of XMMS by mpgedit development, MP3 files edited with mpgedit are known to work properly with XMMS, as well as many other popular media players that playback MP3 files.