mp3HD was created by FhG and Technicolor (formerly Thomson) as a proprietary extension to the MP3 format allowing lossless encoding and playback.

This trick is achieved by encoding a normal MP3 stream, and then grafting into it (actually, in the ID3v2 tag) the discarded data. That way, (most) normal MP3 players can play the lossy track and special decoders can take into consideration the extra data, enabling lossless playback.

Storing the lossless data in the ID3v2 tag poses problems by itself: some decoders do not understand this information and interpret that the file is corrupt. Also, some tag editors do not recognize that kind of data and remove it upon updating the tag. Finally, the ID3v2 specification limits the tag size to 256MB, therefore the lossless data can not exceed that size (most full CDs, at 75-80 minutes, would easily do so if encoded as a single file).

This mode of operation - lossy stream plus discarded data to achieve lossless compression - is the same idea employed by WavPack hybrid mode, OptimFrog DualStream and ATRAC Advanced Lossless. The performance is decent: in my limited tests, mp3HD yielded compression ratios a little better than FLAC's (but keep in mind performance tends to be worse when encoding VBR MP3s).

Just like MP3pro and MP3 Surround, mp3HD failed to become popular and was quickly abandoned by its creators. Fortunately, you can still visit a mirror of the original web page at the Internet Archive.

Compression performance in my limited test: 54.38% (with CBR 128)

Thanks to Zachary Jelesoff for sending me this file and reminding me of the existence of mp3HD!


Date: 2010-02-02
Version: 1.5.0
Interface: Command line + Winamp plugin
Platform: Win32/Linux/Mac OS X
Download: mp3hdtl.zip - 1.932kB