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AAC (Apple, Nero), Vorbis and MP3 (rock, metal), Personal listenting test at ~64/~80 kbit/s
post Sep 14 2009, 05:19
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1. HE-AAC: Apple vs Nero (64 kbps)
2. Apple LC-AAC vs Apple HE-AAC vs Vorbis (80 kbps)
3. LAME (130 kbps) vs others.

1) Lame 3.98.2 -V5.9 (~130-135 kbps). Mainly as high anchor.
2) Aotuv b5.7[20090301] -q1.05 (~80-85 kbps)
3) itunes (constrained VBR, 44100 Hz, stereo):
3a) LC-AAC 80 kbps
3b) HE-AAC 80 kbps
3c) HE-AAC 64 kbps
4) Nero -q0.23 (~64 kbps)

[Shifting] Bitrates
This bitrate table based on 10 full albums (12 CDs)

Observations of bitrate table:
1. A general criteria was that the difference between bitrates should be less than 2%. An exception was Apple LC-AAC that exceeds +2.1% in bitrate comparing to Apple HE-AAC. iTunes hasn't -q values to shift bitrates. It's not big deal for me about +/-2%.
2. Aotuv was slightly shifted from q1.0 to q1.05. I know that it's very light shift comparing to the bitrate variation per each album but Aotuv -q1.0 had almost always (slightly) inferior bitrates comparing to Apple LC-AAC 80 kbps. -q1.05 fits well to be compared to both (Apple LC- and HE-AAC)
3. LAME was shifted from -V5 to -V5.9 to produce around 130 kbps on rock&metal albums. idem Nero.

Samples (original and encoded) with ABC/HR logs
.... will be uploaded soon.

Headphones Sennheiser HD 447. Soundcard Audigy SE 24/96.


Importante observation:
1.Sometimes Apple HE-AAC at 64 kbps was ranked higher than the same encoder but at 80 kbps. I performed few times ABX tests and the results were the same. In past some people reported the similiar issues around Nero and Lame codecs.
2. Nero is working on its new encoder. So Nero encoder is here only as reference to show if Apple did any progress on low bitrate area.
3. I've also included a geometric mean score. I tend to beleive that the geometric mean is more realistic when it's come to judge the results when desviation between average score and some of particular results is something to be considered.

Average score. Geometric mean score is in the parentheses.
1. LAME 130 kbps    - 3.87 (3.80)
2. Apple LC-AAC 80  - 3.35 (3.26)
3. Vorbis 80        - 2.97 (2.84)
4. Apple HE-AAC 80  - 2.85 (2.79)
5. Apple HE-AAC 64  - 2.67 (2.61)
6. Nero HE-AAC 64   - 2.38 (2.30)

Before to do any conclusion it's worth to mention that it is personal test and on rock/metal music only (despite some classic music, progressive stuff, music from different cultures ...etc.. are included).

1. LAME at 130 kbps is still better than newer generation codecs at 64-80 kbits/s
2. Vorbis doesn't shine at 80 kbits/s but it's still on par with Apple HE-AAC and not that far from Apple LC-AAC. Vorbis presents very clear audible distortion at this bitrate. From my experience Aoyumi's Vorbis encoder is an excelent and well tuned for bitrates >=96 kbits/s.
3. Apple LC-AAC 80 kbits/s. Its performance is good for this kind of bitrates.
4. Apple HE-AAC 80 kbits/s. Many times I ranked HE-AAC 80 the same way or even worse than HE-AAC 64. Mainly because a SBR'es efficiency is limited at this bitrate. All test papers (mainly Coding Techs) indicate comparisons where SBR was design to bring the best advantage comparing to non SBR AAC at 48 kbits/s. There are no mentions about official direct 64 kbit/s comparisons. It's still good at 64 kbits/s but not that good for 80 kbits/s.
5. Apple HE-AAC 64 kbits/s. Overall it's slightly better than Nero.
6. Nero HE-AAC 64 kbits/s. I tested almost outdated version of Nero encoder. New encoder might be better.

Any thoughts and suggestions are welcomed. smile.gif

This post has been edited by IgorC: Sep 14 2009, 05:39
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