rockbox/manual/plugins/vbrfix.tex

\subsection{VBRfix}
This function scans a VBR (Variable Bitrate)
MP3 file and updates/creates the Xing VBR header. The Xing header
contains information about the VBR stream used to calculate average bit
rate, time information and to more accurately fwd/rew in the stream.
This function is especially useful when the playback of a file skips,
fwd/rew does not work correctly or the time display is incorrect. 

\opt{recorder,recorderv2fm,ondio}{
\note{Run VBRfix on files you record with your \dap. The header is not present
in the recorded files and VBRfix adds this header.}}

\note{VBRfix can only run when music is
  turned off (since it uses the same memory as the player) and can take a
  while to complete if run on big files.}