32kbps audio public listening test underway at Roberto's site

July 4, 2004

Up until now, the most of Roberto's listening tests were done to find out which codec gives near-transparency to CD quality. This time at Roberto's public Listening Test, a 32kbps multi-codec test is being carried out. Many music download services and streaming radio stations still use this bitrate to allow for real-time streaming to dialup users as well as save on bandwidth. While no audio codec at 32kbps is anywhere near transparency, the purpose of this test is to find out which codecs would be best suited for low bitrate usage.

The codecs used in this test are MP3, HE-AAC, OGG Vorbis, Real Audio, QDesign, WMA9, MP3Pro and High anchor. All encodings were done using 32kbps CBR only since VBR is not-suitable for dialup users due its unstable bitrate.

Unlike the 128kbps listening tests, headphones are not essential in this case since most defects at this low bitrate can be heard on almost any speaker setup. Anyone interested in the quality of low bitrate encodings or are interested in helping to improve this test is welcome to take part in the test.

With most modern formats reaching transparency, or getting close to it, at 128kbps as my Multiformat at 128kbps listening test demonstrated, the real arena where codecs are competing, and most development is going, is at low bitrates. There are important reasons for that: dial-up streaming, storage savings, bandwidth savings for the streaming station... such low bitrates can also be useful for 1 CD DVD rips.

This test's purpose is simulating a dial-up streaming feed. For that reason, bitrates are kept at 32kbps CBR, and VBR isn't being used.

The encoders and parameters tested are:

LAME encoder 3.96 -b 32
Ahead HE AAC+PS 32kbps CBR High Quality
Ogg Vorbis post-1.0.1CVS --managed -b 32 resampled with SSRC
Real Audio 32kbps stereo music codec in Helix Producer 10
QDesign Music Codec 2 Pro 32kbps at 32kHz, Quality mode
Microsoft WMA9 Std 32kbps at 32kHz
MP3pro 32kbps at 32kHz, in Adobe Audition 1.5
High anchor lowpassed at 7kHz with Sox 12.17.4

Who should take the test?

Anyone interested in audio quality at very low bitrates. Or people that have no interest but would like to help making this test better.

How do I take the test?

Download ABC/HR + the readme file from one of the following locations:

http://pessoal.onda.com.br/rjamorim/abc-hr_bin.zip

http://audio.ciara.us/test/abc-hr_bin.zip

Instructions on how to participate are available in the readme.txt/readme.htm file inside the abc-hr_bin.zip package.

If you use BitTorrent, you can download .torrents for the sample packages here: http://www.rarewares.org/torrents/

If you can't use BitTorrent, you can find standard HTTP links inside the readme file

I'm on Linux/MacOS/something other than Windows. Can I take the test?

Yes! Thanks to schnofler, any person using an Operational System with Java can participate. Instructions are available inside the ABC/HR package (Readme.txt and unix-instructions.txt).

You can convert the .bat files to .sh using this Perl script kindly contributed by Mr. Guillaume Cottenceau

When will the test finish?

The test is scheduled to end on July 11th

If you have any other question, please get in touch.

Thank-you very much,

I have seen many codecs claiming FM radio quality at 32kbps. However, in my opinion most of these codecs sound much like AM in stereo with a fair bit of clipping. Eircom's OD2 music download service in Ireland provides 30 second sample clips using WMA 9 at 32kbps and the same low bitrate goes with their 1c per full song streaming service.

To take part in this listening test, visit Roberto's public listening test page here. Feel free to discuss and find out more about audio codecs on our Audio Forum.

Source: Roberto's 32kbps public listening test