I apply track gain to all my MP3 files as I usually listen in shuffle mode. Now when MP3Gain processes the files, it always freezes the whole system for a second or so, whenever it has finished processing a song and is presumably writing the new data to it.

For example it is impossible to listen to music on my Foobar2K player while regaining MP3s with MP3Gain because the current song will start to screech like mad when the system freezes every few seconds or so.

I tried using "improved MP3Gain" for it's supposed hyperthreading support, but that didn't seem to work at all, at least not with the GUI app.

Finally an additional question: The "Replay Track Gain" feature in FB2K doesn't seem to be the same as what MP3Gain does, correct? I can't see any way to set the volume to start with.

First, some baseline terminology, because replaygain and mp3gain can be mixed up and confusing.

Replaygain is an algorithm for determining perceived loudness of a song.

Both mp3Gain and foobar2000 can scan songs and calculate replaygain values, and write these values as tags to the file. Foobar2000 can scan for any audio format, and for mp3 will write whatever sort of tags it is specified to use generally (mainly id3v2 or apev2). Mp3gain used to write the tags as ape tags (I haven't used it in awhile, it's probably still the same).
Some programs can read replaygain tags and adjust playback volume level accordingly.

Mp3gain refers to the program, but is also often used to refer to the processing of mp3's to adjust their volume losslessly by changing the header of each frame. Such processing is limited to increments of 1.5 dB. foobar2000 can do this also, by choosing "apply replaygain to mp3 data" from the context (right-click) menu.
This kind of processing is useful because most programs and hardware do not read replaygain tags and adjust playback volume levels accordingly.


Now, as to your problem. It sounds like Mp3gain is sucking all of your system's processing power when it applies gain values to the mp3 data. Can you adjust the priority? Maybe it's set on high, or even if it's set on normal, try changing it to background or idle or below normal.

Make sure you have DMA enabled for your hard drives. Also try increasing the playback buffer size for foobar.

First of all, thank you for your friendly answers.

DMA was already set on both IDE channels and buffer length for FB2K was 1000 ms. I doubled this now.

I don't know how MP3Gain manages to bring my system to a halt, it's 3,2GHz with 2GB RAM. I already tried changing the priority settings but that didn't help.
I would love to simply use FB2K instead, as I'm using it anyway. But even though I know that context menu command, I don't see where to set the perceived loudness. In MP3Gain it's usually 89 dB and I'm quite sure FB2K sets the tracks to a louder level.