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This article is from the MPEG FAQ, by Frank Gadegast phade@cs.tu-berlin.de with numerous contributions by others.

49 Someone told me that in the ITU-R tests, there was some trouble with Layer-3, specifically on male voice in the German language. Still, Layer-3 got the recommendation for "commentary links". Can you explain that? (MPEG Audio Layer-3 Applications)

Yes. For commentary links, the quality requirements for speech were to be
equivalent to 14-bit linear PCM, and for music, some perceptible
impairments were to be tolerated. In the test in 1992, Layer-3 was by far
the only codec that fulfilled these requirements (e.g. overall monophonic,
Layer-3 scored 3.6 in contrast to Layer-2 at 2.05 - and for male German
speech, Layer-3 scored 4.4 in contrast to Layer-2 at 2.4).
Further tests were performed in 1993 using headphones. They showed that
MPEG-1 Layer-3 with monophonic speech (the test item is German male
voice) at 60 kbps did not fully meet the quality requirements. The ITU
decided to recommend Layer-3 and to include a temporary footnote that
will be removed as soon as an improved Layer-3 codec fulfills the
requirements completely, i.e. even with that well-known critical male
German speech item (for many other speech items, Layer-3 has no trouble
at all).

 

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• prev: 48 I see. Medium bitrates - Layer-2, low bitrates - Layer-3. What's about a bitrate of 96 kbps per channel that seems to be "somewhere in between" Layer-2 and Layer-3 domains? (MPEG Audio Layer-3 Applications)
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• next: 50 O.K., a Layer-2 codec at low bitrates may sound poor today, but couldn't that be improved in the future? I guess you just told me before that the encoder is not fixed in the standard. (MPEG Audio Layer-3 Applications)

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