The test file was encoded with Yamaha's TwinVQ encoder and decoded using JAEP's plugin for WinAmp. This plugin is an interface to NTT's decoder and code book and so gives the same audio quality as using Yamaha's player but you can save the output as a wave file.

NTT TwinVQ HQ 96kb/s Frequency Response

NTT TwinVQ HQ 96kb/s Spectral View

When we look at the frequency response of a 96kb/s VQF file encoded at high quality we see that the output extends right up to 22kHz. The frequency response above 12kHz is suppressed a bit when compared to the source material. It is this suppression of higher frequencies I believe that leads to the slight loss of treble detail as compared to the original.

When we look at the the spectral view of the VQF file we see an amazing correlation to the spectral view of the source material. There is some suppression of material above 20kHz and almost no degradation below 20kHz. This is really superb considering that the file is two thirds the size of a 128kb/s MP3 file.

Listening tests reveal no noticeable encoding artifacts. This holds for source material that produces noticeable artifacts in 128kb/s MP3 encoding such as the Local Hero live recording I mentioned earlier. In some recordings the VQF file tends to lack some presence when compared to the source material. Even with headphones you can hear that the VQF file does not  have as good stereo imaging as an MP3 files for complex material.

I personally would almost always choose a 96kb/s VQF file over a 128kb/s MP3 file. This is because I am far more tolerant of reduction in stereo imaging in a recording than encoding artifacts. In most instances I would say 96kb/s VQF files are not as good as 160kb/s MP3 files. This is definitely true for the source material reviewed here.

CPU utilization on my system for playback is an acceptable 35%. The major drawback of VQF encoding is that it is very slow.

I feel that TwinVQ is definitely an alternative to MP3 for mainstream usage especially in portable applications like Walkman type players. I would not be surprised to see "music on a chip-card" type players from Yamaha in the near future.

I hope to see NTT or Yamaha release a 128kb/s version of their codec soon as this should eliminate the shortcomings of 96kb/s files.

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