mp3HD: New lossless MP3 format explained

French media behemoth Thomson has announced mp3HD, a new lossless 'hybrid' MP3 format, which not only offers the sound detail lost in a normal MP3, but remains compatible with your existing MP3 player or iPod.

It's called mp3HD and still uses the traditional .mp3 file extension. Simply put, it works by storing a conventional lossy MP3 track that standard players can play, alongside a 'lossless' version -- both audio streams are contained in one single MP3 file. It's similar to how hybrid SACDs work.

Ideally this would appeal to users who want to enjoy lossless audio at home, and universally compatible MP3s on the commute, without having to rip two versions of the same song.

Real-world testing

We've tested the format, ripping our own CDs using Exact Audio Copy and Thomson's mp3HD command line encoder. A 6 minute 22 second mp3HD file (Pink Floyd's Money), using default settings, gave us a 48MB file -- just 5MB larger than a file ripped in FLAC, level 8.

On a PC with Thomson's mp3HD decoder plug-in installed, WinAmp played the 800Kbps (on average) lossless audio track, but when dragged into iTunes the same file played as a normal old 320Kbps MP3 file. It transferred without issue to an iPhone 3G and to a Cowon iAudio D2 MP3 player, and played without any problems.

This is it: a lossless audio file, theoretically backwards compatible with all existing MP3 players! Why wouldn't everyone adopt this? Well, for a whole bunch of reasons, frankly.

The problems

At face value it's remarkably convenient, like a car that doubles up as a plane. But like your aeromobile, there are problems for the average consumer. Firstly, file size. A normal 320Kbps MP3 of the same Pink Floyd song was just 14.6MB, and 320Kbps is all you'll hear if you listen to an mp3HD track on your iPod.

But the lossless audio stored in the file will be stored on your iPod nevertheless, taking up precious storage space. (Although we should point out to audiophiles that the hybrid files are smaller than the combined size of a FLAC and 320Kbps MP3, although are less efficient to encode than FLAC.)

The second problem concerns compatibility. The joy of MP3 files, and the reason for their ubiquity in the marketplace, is their small size and compatibility with almost anything you throw at them. With mp3HD, not only are file sizes massive (making them impractical for small flash players), but you need to install plug-ins on your computer. True backwards compatibility would mean no additional software or updates were required.

Ideally you'd be able to transfer only the small, lossy part of the mp3HD to a portable player, leaving the lossless part (stored as what's known as 'correction data') behind. But this would require additional software, and that means Average Joe won't want to know about it.

The last word

In conclusion, mp3HD will undoubtedly appeal to archivists with hard drives in their portable music players (such as the iPod classic or Archos 5). But for the chap on the street it'll be small, convenient, decent-enough-sounding MP3s all the way, and smaller Apple Lossless files for the iTunes audiophiles.

You can get started using the format at Thomson's Web site.