Public AAC Listening Test @ 96 kbps (July 2011)

The purpose of this test is to find out which popular AAC encoder outputs the best quality on bitrates around 96 kbps.

• Which codecs and settings are tested?

  • Nero 1.5.4
    -q 0.345
  • QuickTime True VBR (via qtaacenc)
    --tvbr 46 --highest --samplerate keep
  • QuickTime Constrained VBR (via qtaacenc)
    --cvbr 96 --highest --samplerate keep
  • Fraunhofer IIS (via Winamp 5.62)
    VBR 3
  • Coding Technologies (via Winamp 5.61)
    CBR 100 kbps
  • ffmpeg's AAC @ 96 kbps (Low Anchor)
    -acodec aac -ab 96k -strict experimental

• Is it normal that the bitrate is very high on some samples (even 228 kbps)?

  Yes, and that is 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 is the best way to compare modern codecs that shine most in VBR mode. Trying to force a VBR setting to match a desired bitrate, although fairer, is far from the usual practice of audio encoding, where it's more usual that a user just sticks to a quality setting, not caring much about a specific bitrate.

  The quality settings for the VBR codecs were chosen because they average out to about 96 kbps 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 who have no interest but would like to help making this test better are invited. You don't need excellent hearing, but some good gear is welcome. Headphones are a must-have.

• How do I take the test?

  Download ABC/HR and the readme from the following location:

  • ABC-HR_bin.zip

  If you already have ABC/HR, download the readme from here:

  • readme.txt
  • readme.htm

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

  Please note: if you don't hear any sound when using ABC/HR, simply change the device from ABC/HR's settings. In some cases, ABC/HR might not default to the primary audio driver.

• Can I take the test even if I am not running Microsoft Windows?

  Thanks to schnofler, any person running an operating system with Java Runtime Engine 1.5 can participate. Instructions are available inside the ABC/HR package.

  Some users reported that ABC/HR hangs when using the Java Runtime Engine 1.6. In case you are affected, please download and install JRE 1.5 from the following link: http://java.sun.com/products/archive/j2se/5.0_15/index.html. You do NOT have to uninstall JRE 1.6 in order to use JRE 1.5, but please make sure that java.exe from JRE 1.5 is used.

  Since the working directory has to be the location where abchr.jar is stored, the best thing you can do is to open a command prompt window, navigate to the location where you stored abchr.jar and the rest of the files and then call "C:\Program Files\Java\jre1.5.0_15\bin\java.exe -jar abchr.jar". Of course, this is only an example which you have to adapt according to where java.exe is stored on your PC.

• When will the test finish?

  The test is scheduled to end on XXX. This date may be extended if proven to be necessary.

If you have any questions, feel free to contact me via e-mail: listening.tests.ha@gmail.com.

Best regards

© Sebastian Mares, 2011 | Layout by Dibrom | Portions of the Text by Roberto Amorim