IVolume

iVolume is an application for Mac OS X and Windows that implements ReplayGain for iTunes by updating the metadata that iTunes uses for Sound Check volume normalization.

Sound Check background: If the iTunes Sound Check preference is activated, iTunes scans audio files to determine a per-track playback volume adjustment. Sound Check is designed so that the playback of multiple tracks with inherently varied relative volume levels will be at a consistent volume level.

iVolume aims to improve upon Sound Check by instead applying the ReplayGain algorithm. It replaces the settings computed by iTunes with new values computed via the ReplayGain algorithm. These volume adjustment settings supposedly result in perceptually more consistent playback volume levels than those produced by the iTunes algorithm.

While the CPU consumption of the algorithm employed by iTunes is nearly negligible, iVolume requires a few moments to process each track. This computation can be performed once and the results will be retained in the audio file metadata.

iVolume provides the capability to compute volume adjustments on a per-album basis, whereas iTunes does not. In this mode, iVolume scans all of the tracks in an album to determine the adjustment setting to apply and then it applies the same adjustment to each of the tracks in the album.

iVolume is incapable of processing protected files purchased via the iTunes Music Store and, for these files, only the built-in iTunes Sound Check volume adjustments can be used by them.

Though iVolume is capable of being configured to operate without oversight, unlicensed iVolume will periodically cease processing and display a dialog box soliciting a registration in return for uninterrupted operation. This can have an adverse effect on processing large libraries of music as the dialog box may not be dismissed until a set time has elapsed, the length of which increases by several seconds each time the dialog box is displayed. Furthermore, the unlicensed version stops functioning after analysing 1000 tracks.