Listening Tests at Low Bitrates

Notes by ff123

Caveats: Please note that although I can hear pure tones up to a little over 16 kHz, I cannot hear the difference between a WAV ripped from CD and the same WAV brickwall filtered at 12 kHz (see my page, Test Your Hearing, Part 3). Take that into consideration as you evaluate what my results might mean. Also, as always, the music sample selection has a great influence on the outcome of codec listening tests.

Setup: Fanless computer operation. Grado SR325 Headphones. M-Audio Audiophile 2496 soundcard. MP3 decoder: in_mp3.dll from Winamp 2.76. WMA decoder: in_wm.dll from Winamp 2.6.

Conclusion: Coding Technologies touts mp3PRO at 64 kbit/s as having quality equivalent to regular mp3 at bitrates between 96 kbit/s and 128 kbit/s. Using one of Fraunhofer's best codecs at 96 kbit/s and 112 kbit/s (MMJB 6.1 "very high," or Alternate codec), I'd say mp3PRO quality weighs in nearer to 96 kbit/s equivalent than to 128 kbit/s equivalent. For people with good high-frequency hearing, mp3PRO may sound as good as or perhaps even better than 112 kbit/s regular mp3 in some cases (if they can hear 13 kHz and above in actual music, and heavily weight that part of the frequency spectrum). But for the most part, I would choose the regular mp3 at 112 kbit/s or even at 96 kbit/s, rather than mp3PRO or WMA8 at 64 kbit/s.

See what other people think about mp3PRO's sound quality.

This is an acoustic jazz track called "Tam's Jam" from Michael Garson' Serendipity (RR-20CD). It's not a particularly difficult piece to encode with mp3 at 128 kbit/s, which is part of the reason why I chose it -- I didn't want to use a "killer" sample. Even so, at low bitrates, I can hear problems with various codecs. The 13 second piece I used to test can be found on my Audio Samples Page. The file is called "tamsjam.flac" and has been losslessly compressed using FLAC. MP3Pro lies somewhere between 96 kbit/s and 112 kbit/s regular mp3 in quality for this sample (with my ears). It's possible that others may find mp3PRO to be better than the 112 kbit/s regular mp3 by virtue of its more extended frequency response (which I can't hear).

Ok, now for a killer sample: applaud.wav, which can be found on the Lame Quality and Test Information page. Applause is extremely difficult for encoders, and this is in some ways an unfair sample to choose, because it may not be representative of the type of music many people listen to.

Theme from the Deerhunter, featuring solo acoustic guitar. From a Telarc Sampler Disc. The 30 second piece I used to test can be found on my Audio Samples Page. The file is called "deerhunter.flac" and has been losslessly compressed using FLAC. This sample is transparent to me using normal mp3 at 96 kbit/s.

A Rammstein (heavy metal) tune uploaded by cd-rw.org to his account at http://www.saunalahti.fi/~ljpp/lame/ as 03.pac. This is a complex sample with loads of high frequencies, distorted guitar, and a sound that pans from left to right.

This is from a 70's pop tune, Good Time Charlie's Got the Blues, by Danny O'Keefe. I thought it should have been simple enough, but none of the encoders came close to sounding like the original. The 13 second piece I used to test can be found on my Audio Samples Page. The file is called "charlies.flac" and has been losslessly compressed using FLAC. The normal mp3 at 112 kbit/s is probably "best" (it still sounds bad), but I can't decide how to rank the others, which all sound very bad.

Electronica music (Rushing, by Moby): hihat and piano in the beginning. The crackling sounds you hear later are supposed to be there. The 15 second piece I used to test can be found on my Audio Samples Page. The file is called "rushing.flac" and has been losslessly compressed using FLAC.

Return to ff123's Home Page