[abel]

Does anyone know approximately which bitrate of mp3 approximately corresponds to sp, lp2, and lp4 mode in md ? The reason I want to know this is so I don't waste my time converting say, a 128kb mp3 into an sp track (to say the extreme).

 

[blessingx]

Welcome to Head-Fi.

Obvious lossy to lossy compression is never preferred (though I know it's big in the MD community).

How it corresponds to MP3 depends a great deal on which MP3 encoder (FhG, LAME, Blade, etc.) is used. Sheer numbers though...

Standard ATRAC ("SP") is 292kbps, LP2 is ~132kbps, LP4 is ~66kbps. The LP mode bitrates are not simply 146kbps (292/2) and 73kbps (292/4) for this reason: In LP2 and LP4 modes 20 bytes of dummy data per 212 byte soundgroup are used to keep compatibility with SP mode, making them appear as normal ATRAC soundgroups containing silence. This allows LP2/4 tracks to play as silence on non-MDLP equipment. The intention is that older MD units should not produce random digital noise when playing LP tracks.

From here.