128kbps Extension public listening test

Building on the AAC at 128kbps test results, this test is meant to compare the AAC winner (QuickTime) against other popular compression formats: Musepack, Vorbis, WMA Pro and MP3

It's purpose is to find what encoder outputs the best quality on bitrates around 128kbps

The encoders and parameters tested are:

• Apple QuickTime 6.3 MP4 encoder 128kbps high quality
• LAME MP3 Encoder 3.90.3 --alt-preset 128
• Musepack 1.14 --quality 4 --xlevel
• Ogg Vorbis post-1.0 CVS -q 4.25
• Windows Media Audio v9 PRO bitrate-managed 2-pass VBR 128kbps

• I noticed that, on some files, bitrate goes very high, nearing 200kbps sometimes. Is that right?

  Yes, and that's the beauty of VBR encoding. It will simply ignore bitrate limitations (whenever possible), using as much bits as needed to encode a problematic sample.

  Although that raises issues of fairness, it's the best way to compare modern codecs that shine the most in VBR mode, like Musepack and Vorbis. Trying to force a VBR setting to match as best as possible a desired bitrate, although fairer, is far from the usual practice of audio encoding, where it's more usual that an user just stick to a quality setting, not caring much about a specific bitrate

  The quality settings chosen for the VBR codecs were chosen because they average out to about 128kbps over a number of encoded albums. It would be unfair to tie the hands of VBR codecs and punish them for being smart about where to spend what turns out to be the same number of bits over the long run.

• Who should take the test?

  Anyone interested in lossy audio quality, or people that have no interest but would like to help making this test better. You don't need excellent hearing, but some good gear is welcome (headphones are must-have).

• How do I take the test?

  Download ABC/HR + the readme file + the codecs (1.1Mb) from one of the following locations:

  • http://www.audiocoding.com/test/abc-hr_bin.zip
  • http://audio.samharris.us/rarewares/abc-hr_bin.zip

  Further instructions, and links to the sample packages, are inside the readme.

  The average size of each sample package is 4.5Mb. It sums to 56Mb, all the 12 packages.

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

  You can. But you won't be able to use the ABC/HR utility, that is Win32 only. Since the reference file must be hidden (That's the HR in the name), tests performed without it wouldn't be valid. So, I can't plot your scores against others created with ABC/HR. But your comments on sample quality and artifacts would still be welcome.

• When will the test finish?

  The test is scheduled to end on August 3rd

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

Thank-you very much,

Roberto Amorim.

Back to Roberto's Listening Tests page