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SE listening test @128kbit/s, warning: with artifacts amplification
Serge Smirnoff
post Nov 28 2013, 12:28
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If somebody is interested in results of forthcoming SE listening test @128kbit/s despite questionable artifact amplification technique, that will be used in this test, please, propose your codec candidates.

Results of the test will be presented in the same detailed form as in previous @64 and @96 tests.


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Serge Smirnoff
post Mar 24 2014, 23:21
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Following codecs were added to 128kbit/s section:

AAC VBR@112.0 (Winamp 5.666) - VBR, AAC LC
AAC VBR@118.4 (iTunes 11.1.3) - TrueVBR, AAC LC
AAC VBR@117.5 (NeroRef 1540) - CVBR, AAC LC
Vorbis VBR@119.4 (Xiph 1.3.3)
Opus VBR@115.7 (libopus 1.1)
mp3 VBR@113.7 (Lame 3.99.5) - MPEG-1 Layer 3, VBR
AAC VBR@110.9 (libfdk 3.4.12) - MPEG-4 AAC LC, VBR
mpc VBR@123.3 (SV8)

All encoders have integer/discrete quality settings - http://soundexpert.org/news/-/blogs/opus-a...c-at-128-kbit-s


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C.R.Helmrich
post Mar 25 2014, 10:57
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Sorry if this has been answered before, but: how much error amplification do you apply at 128 kbps stereo? 1 dB, or more?

And I'm surprised Fraunhofer's AAC encoder averages only 112 kbps on this item set. Do some samples include silence?

Chris

This post has been edited by C.R.Helmrich: Mar 25 2014, 10:59


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Serge Smirnoff
post Mar 25 2014, 11:47
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QUOTE (C.R.Helmrich @ Mar 25 2014, 11:57) *
Sorry if this has been answered before, but: how much error amplification do you apply at 128 kbps stereo? 1 dB, or more?

Not all test items were amplified, only those with unnoticeable artifacts.
If amplification was applied then at least three amplified versions of a test item were produced - in most cases with +1dB, +3dB, +5dB amplification. It depends on particular codec/item, in some cases it was even +4dB +6dB +10dB. For higher bitrates amplification is usually higher as well.

QUOTE (C.R.Helmrich @ Mar 25 2014, 11:57) *
And I'm surprised Fraunhofer's AAC encoder averages only 112 kbps on this item set. Do some samples include silence?

SE test set usually results in lower bitrates than pop-music. It is closer to classical music material. Yes, some items contain silence. SE test sequence can be downloaded from http://soundexpert.org/sound-samples (bottom of the page)


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LithosZA
post Mar 25 2014, 13:09
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QUOTE
Not all test items were amplified, only those with unnoticeable artifacts.

I assume the same amplification would be applied to all codecs for that item?
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Serge Smirnoff
post Mar 25 2014, 13:26
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QUOTE (LithosZA @ Mar 25 2014, 14:09) *
QUOTE
Not all test items were amplified, only those with unnoticeable artifacts.

I assume the same amplification would be applied to all codecs for that item?

No, as each test item is degraded by each codec differently, in each item/codec case the amplification is applied differently (if at all). If applied - three gradually degraded versions of an item are produced.


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C.R.Helmrich
post Mar 25 2014, 13:40
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QUOTE (Serge Smirnoff @ Mar 25 2014, 13:26) *
... each test item is degraded by each codec differently, in each item/codec case the amplification is applied differently (if at all). If applied - three gradually degraded versions of an item are produced.

But then how can you rank the codecs for such items?

Chris


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Serge Smirnoff
post Mar 25 2014, 14:29
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QUOTE (C.R.Helmrich @ Mar 25 2014, 14:40) *
QUOTE (Serge Smirnoff @ Mar 25 2014, 13:26) *
... each test item is degraded by each codec differently, in each item/codec case the amplification is applied differently (if at all). If applied - three gradually degraded versions of an item are produced.

But then how can you rank the codecs for such items?

Two page doc explains the whole procedure of ranking - http://soundexpert.org/documents/10179/11017/se_igis.pdf
In short. Three (or more) gradually degraded test items are graded by testers as usual. Each test item then has two coordinates - level of waveform degradation (Difference level, dB) and subjective score [1-5]. These three points define a 2-nd order curve which shows the relationship between measurable degradation of waveform and perceived degradation of sound quality. Resulting score of the codec in such case is the point on the curve corresponding to Difference level of the item without amplification.


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