HE AAC Audio Quality & Tuning Options

[GreenSeer]

I am new to the lossy coding world. I recently became a DROID owner and, in an effort to get down to carrying one device, I ripped all of my music to my DROID at 64 kbps. In the environments I often listen in (Airports, Planes, Rental Cars, Taxi's, etc.) this is good enough for me and has the great benefit of using minimal storage space. The efficiency of a codec that provides satisfactory audio quality while using lower bitrates appeals to me.

My question is whether this codec is still being developed and "tuned"? I guess I am curious as to whether HE-AAC is now about as good as it will ever get. For example, is the crossover point from real sound to where the SBR begins as finely tuned as possible? Will we ever get to the point where a 48 kbps rip is perceived qualitatively by a general audience like a 128 kbps AAC file is today? Thanks!

[IgorC]

Chris,

The Average scores are:

Apple HE-AAC - 2.85
FhG HE-AAC - 3.01

One would think that the difference is pretty small. Yes, but I've performed the test on these codecs before and the results were the same. Let me see if I can find those results on my hard disk later.
Also the scores are pretty low because I didn't include the low anchor. The quality is actually pretty good and if it was a public test the average scores would be in range of 3.9-4.0.

CODE

Apple HEAAC FhG HEAAC
3 3,7
4,1 4
1,8 4,3
3,2 3,2
3,1 2,8
1,5 1
2 2,4
3 3
2 3,1
1 1,7
3 3,1
1 1
2,7 3,5
3,2 3,6
3,8 3,8
1 1
3,8 3,8
2,5 2,5
4 3,6
3,4 3,1
2 2,5
3,3 3,5
3,4 3,4
3,5 4
3,4 2,9
3,3 3,3
3,3 3,6
3,4 3,2
4 3,8
2,8 1,8

I won't post here particular ABC/HR logs as this test wasn't meant to be published. Nothing special, just private stuff.

Those are 30 samples from public test 64 kbps (2011). There were some pathological cases where both encoders don't perform well. Those are classical transient samples like castanets, fatboy and eig.
FhG did a good job comparing to Apple on all samples except the last one. Sample30. It was also a difficult sample for FhG LC-AAC encoder in last public AAC test.
It will be great to see an updates of your encoder.

[C.R.Helmrich]

Awesome, thanks a lot, Igor!

FhG did a good job comparing to Apple on all samples except the last one. Sample30. It was also a difficult sample for FhG LC-AAC encoder in last public AAC test.

Yeah, that Sample30 (or 20 in the 96-kbps test) is a pain. I recently added a minimally invasive patch which gives a bit more (hopefully enough) bit-rate to that item without affecting others much. Once that encoder version becomes publicly available, I'll let you know.

Chris

[C.R.Helmrich]

I recently added a minimally invasive patch which gives a bit more (hopefully enough) bit-rate to that item without affecting others much. Once that encoder version becomes publicly available, I'll let you know.

Bump. Just found a forum post saying that Winamp 5.63 has been released. Relevant quotes from the release notes:

* Improved: [enc_fhgaac] Added VBR mode 6, plus other minor quality improvements
* Fixed: [aacdec] Memory leak when re-syncing to AAC stream
* Updated: [aacdec] Fraunhofer AAC Decoder v1.762.208

Chris

[sluggy]

I recently added a minimally invasive patch which gives a bit more (hopefully enough) bit-rate to that item without affecting others much. Once that encoder version becomes publicly available, I'll let you know.

Bump. Just found a forum post saying that Winamp 5.63 has been released. Relevant quotes from the release notes:

* Improved: [enc_fhgaac] Added VBR mode 6, plus other minor quality improvements
* Fixed: [aacdec] Memory leak when re-syncing to AAC stream
* Updated: [aacdec] Fraunhofer AAC Decoder v1.762.208

Chris

Hi i have tried encoding in vbr 6 and i find there is hardly any increase in bitrate between 5 and 6. Could you please give me some more info in the changes?

[benski]

Hi i have tried encoding in vbr 6 and i find there is hardly any increase in bitrate between 5 and 6. Could you please give me some more info in the changes?

I just tested on a "difficult" (kraftwerk-style electronic music) track and saw a substantial difference, 222 kbps for VBR5 and 277 kbps VBR6. For "easy" material, particularly when lacking in high frequency energy, you might not see much of a difference.

[sluggy]

Hi i have tried encoding in vbr 6 and i find there is hardly any increase in bitrate between 5 and 6. Could you please give me some more info in the changes?

I just tested on a "difficult" (kraftwerk-style electronic music) track and saw a substantial difference, 222 kbps for VBR5 and 277 kbps VBR6. For "easy" material, particularly when lacking in high frequency energy, you might not see much of a difference.

Ok thanks for the info, yeah the audio was prob easy to encode like you said, its good to see updates on this already excellent encoder