🚀 go-pugleaf

>There is an MPEG-4 standard, but it's not issued yet.
>There is a new MPEG audio standard in MPEG-2 that is issued,
>that has shown much better performance than MP3 or any of the other
>tested algorithms in tests run with known and well-tested encoders
>of good performance.



I suggest all interested readers get
<http://www.cselt.it/mpeg/public/w2006.zip>

This is a 45 page Word 6 doc with graphs & tables.

It is dated Feb 98, called

ORGANISATION INTERNATIONALE DE NORMALISATION
ISO/IEC JTC1/SC29/WG11
CODING OF MOVING PICTURES AND AUDIO

Report on the MPEG-2 AAC Stereo Verification Tests

David Meares, BBC R&D, Kingswood Warren, UK
Kaoru Watanabe, NHK, Tokyo, Japan
Eric Scheirer, MIT Media Labs, USA

31 listeners in the field of professional audio took part in a
double-blind test. 2-3 in the room at a time. 30 min per session. 8
sessions per person over two days. A statistical analysis of seat
position was undertaken and the first two seat positions were found
to give reliable results so the third seat position was dropped
leaving 22 listeners. Ten solo instrumental and musical excerpts
were presented in a 30-min session. Guided listener training was
performed beforehand.

From Figure 5. The mean Diffscores (estimated off graph) were

AAC Main 128 .18
AAC LC 128   .22
AAC SSR 128  .35

AAC Main 96  .55
AAC LC 96    .68

MP2 192      .70
MP3          .95

Q. "Is the performance of the AAC codecs at the tested bitrate
achieving 'indistinguishable quality' in the EBU definition of that
phrase?"

A. "Thus, we see the the AAC Main 128 and LC 128 codecs provide
'indistinguishable quality' in the EBU sense of the phrase."

Mean score of the *lowest* test result of the most critical
(i.e. lowest-rated) test item for each codec. [DB: This is not the
average of each codecs results but it is the worst result for any
of the 10 tests (i.e. when the encoder experiences its greatest
failure in hiding its manipulations)]


AAC Main 128 4.42
AAC LC 128   3.85
AAC SSR 128  3.74

AAC Main 96  3.48
AAC LC 96    3.14

MP2 192      2.32 (on the Pitch Pipe sample)
MP3          1.63 (on the Pitch Pipe sample)

Where
5 = Imperceptible
4 = Perceptible but not annoying
3 = Slightly annoying
2 = Annoying
1 = Very Annoying


Conclusions:

The overall conclusion is that, when auditioning using
loudspeakers, AAC coding, according to the ISO/IEC 13818-7 standard
gives a level of stereo performance superior that given by MPEG-1
Layer II and Layer III coders.

The test process was intended to answer the following set of
questions which form the detailed conclusions of this study:

Q. Is the performance of AAC codecs at the tested bitrate equal to or
better than the performance of MPEG-1 Layer II and Layer III?
A. Section 10.6 presents the answer to this. Overall, all AAC
profiles at 128 kbps give significantly better performance than do
MPEG-1 Layer II at 192 kbps or Layer III at 128 kbps. Therefore the
goal of high audio quality at 64 kbps per channel for MPEG-2 AAC has
been achieved. Both AAC Main Profile and Low Complexity Profile
provide quality at 96 kbps that is comparable to MPEG-1 Layer II at
192 kbps, and therefore give a 2 to 1 compression advantage. In
addition, AAC Main Profile at 96 kbps gives better results than
MPEG-1 Layer III at 128 kbps.

Q. Are the listeners' results reliable, i.e. distinguishable from
random votes?
A. The analysis conducted in Section 10.2 concludes that all listeners
returned reliable results.

Q. Does the test methodology allow meaningful conclusions to be drawn
from these results?
A. The analysis confirms that meaningful conclusions can be drawn from
these results. The effect SEAT was shown to be significant in its
own right, particularly with reference to the rearmost seat
position. However, as there were only a limited number of listeners
who used this position and as the results from the other two seats
could be combined, the further analysis only made use of the results
from the front and centre seat positions.

Q. How does the performance of the codecs vary with programme items?
A. This is shown in full in section 11. It is shown that all coders
perform, to some extent, differently depending on the type of
programme item with which they are being tested.

Q. Is the performance of the coding of AAC codecs at the tested
bitrate distinguishable from the original signal?
A. Sections 10.7 and 11 show that there is a statistical difference
between the source and coded items, both overall and for some
specific items. However, there were a large number of items for
which no difference was recorded.

Q. Is the performance of AAC codecs at the tested bitrate achieving
`indistinguishable quality' in the EBU definition of that phrase?
A. AAC Main Profile at 128 kbps and AAC Low Complexity Profile at 128
kbps both provided `indistinguishable quality' and AAC SSR Profile
at 128 kbps failed to achieve this by margin of less than 1%
relative to the decision criterion.

Q. Is the following requirement of ITU-R Recommendation BS.1115 [5]
fulfilled?
"For emission, the most critical material for the codecs must be
such that the degradation may be `perceptible but not annoying'
(grade 4)."
A. AAC Main Profile at 128 kbps passes this criterion.


Give me AAC, please
Cheers, Dan.