The non-tech media's been full of articles deploring the inferior sound of the MP3 era. Apparently Pioneer agrees. At CES, the company is demonstrating technology it calls Advanced Sound Retrieval, or ASR, which promises to restore some of the signal lost when audio is compressed into a "lossy" format like MP3 or compressed WMA or AAC.
Technically, it's much tricker to restore signal than it is to cut it--that's one of the first rules of audio recording, which is why you want to get the broadest dynamic and frequency range possible, then pare it down, rather than trying to fill it in later with effects and EQ. What Pioneer appears to be doing is looking at the signal from moment to moment, making an educated guess about signals with frequencies above 15kHz that have been cut, and reinserting those signals.
I didn't get to test it at real world volume, in a real car, with music I know and love, so it's hard for me to be objective. But at the booth, when I listened to an MP3 file of Rage Against the Machine with ASR on and off, I definitely noticed a lot more high end with the ASR on. But it didn't sound louder--it's not like the Loudness button you used to see on some stereos (which was basically a compressor...that's another post). And it wasn't as if somebody simply turned up the EQ on the high end. So, it does seem as if Pioneer's doing some pretty sophisticated work here, and it probably will make your compressed audio files sound better--not CD-quality, but better.
As a sidenote, a huge thanks to the person who programmed "Scratch" by Morphine into one of the Gigabeats at Toshiba's booth. Most demo music at CES is brash and trebly, so it was a pleasure to hear all this low-mid--bari sax, upright bass, and a baritone singer. It also happens to a personal favorite: it's one of the only cover songs an old band of mine used to do. It was a great way to take a five-minute break on the floor. And I still think the Gigabeat was a beautiful-sounding MP3 player that got caught in the PlaysForSure crossfire--in fact, that's probably why I enjoy listening to my first-generation Zune so much, as it's basically just a rejiggered Gigabeat.