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AAC 320 VBR question
SpyGuy
post Nov 16 2012, 01:07
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I'm looking at buying a new head unit for my car, a Kenwood Excelon KDC-X896. According to the specs it can handle AAC-LC format from 8-320KBPS.

Here's my question. I'm using Foobar2000 to convert my lossless songs into VBR AAC at q 0.76 which is roughly 300KBPS. The thing with VBR though, is that it swings, on tough passages it might go as high as 340 or maybe even more.

So here's my question. On devices that say they can handle 320 VBR, do these spikes show up as pops or artifacts, are they just not played back for that millisecond? Do I need to find a q setting low enough so that any spikes stay below 320? Or by saying that it can handle 320 VBR, Kenwood is saying it can handle any spikes at 320 (which can go as high as nearly 380 according to some googling I do).

Apparently iPods have this same specification, 8-320kbps VBR, but I'll have to get my hands on one to see how they handle it.
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cyberdux
post Nov 16 2012, 02:24
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For what it is worth, AAC encoded by the Nero encoder at >400kbps play perfectly on all my "i" devices.

Having said that, I routinely use around 256kbps on these devices.
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eahm
post Nov 16 2012, 02:36
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You may want to ABX, you may even not be able to hear artifacts at 96kbps and may save a lot of space and copy more music on your device. Again, AAC achieves transparency at 128kbps and your car (any car) will NOT play music better than computers, hi-fi stereos, headphones...

Nero also is no longer the best way to encode AAC files, I suggest you to configure qaac with foobar2000. With qaac and Apple libraries you can achieve the highest quality AAC files, you can also create them with True VBR setting and qaac is configurable in a portable way (no need to install any Apple software like iTunes or QuickTime).

This post has been edited by eahm: Nov 16 2012, 02:57
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cyberdux
post Nov 16 2012, 07:15
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QUOTE (eahm @ Nov 16 2012, 11:36) *
You may want to ABX, you may even not be able to hear artifacts at 96kbps and may save a lot of space and copy more music on your device. Again, AAC achieves transparency at 128kbps and your car (any car) will NOT play music better than computers, hi-fi stereos, headphones...

Nero also is no longer the best way to encode AAC files, I suggest you to configure qaac with foobar2000. With qaac and Apple libraries you can achieve the highest quality AAC files, you can also create them with True VBR setting and qaac is configurable in a portable way (no need to install any Apple software like iTunes or QuickTime).

Agreed. My post was merely to confirm that >320kbps lossy AAC was "playable" on 'i' devices.
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Engelsstaub
post Nov 16 2012, 09:16
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QUOTE (cyberdux @ Nov 16 2012, 01:15) *
...My post was merely to confirm that >320kbps lossy AAC was "playable" on 'i' devices.


They will. I've had VBR files that reached over 340 Kbps play back just fine on both my iPod Touch while interfaced with my (older) Alpine head unit in my vehicle.


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Porcus
post Nov 16 2012, 11:33
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Is there any essential difference between AAC at average 320 but transient higher reported rate, and MP3 at 320 but with optimized use of bit-reservoir, or does it really boil down to reporting by the software?


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SpyGuy
post Nov 16 2012, 21:53
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I spent some time last night reading up on qaac and then configuring it with Foobar. Its a nice little encoder and I like the TVBR aspect. I got a hold of my brother's iPod and it does indeed play VBR above 320, I encoded a half a dozen songs at V -127 which gives bit rates in the 350+ range, and the iPod had no problems. Makes me feel good that this Kenwood unit might have the same performance. If not, I think going down to a lower bit rate won't be a big deal. Thanks for the heads up on qaac.
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neothe0ne
post Nov 19 2012, 06:17
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I've had some 320 VBR M4A files refuse to play on my iPod (unfortunately, iTunes will play it and sync it without complaining)
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eahm
post Nov 26 2012, 08:45
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My bad I was preaching too much for AAC, a new page is out that claims AAC reaches transparency at ~150kbps http://wiki.hydrogenaudio.org/index.php?title=Transparency

I'm waiting for the new iTunes 11, let's see if it will bring new libraries then I'll reconvert all my portable music to -V73.

This post has been edited by eahm: Nov 26 2012, 08:49
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IgorC
post Nov 26 2012, 13:41
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The mention of transparency of AAC at 150 kbps is dated by 16/10/2004
By that time the best AAC encoder (iTunes) was only CBR.

Later (14/01/2006) there was the public test which has shown that AAC was transparent at ~128 kbps (VBR)
http://listening-tests.hydrogenaudio.org/s...8-1/results.htm
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eahm
post Nov 26 2012, 15:22
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Since the test are old and encoders are much improved, is it safe to say Apple True VBR is transparent at ~128kbps?
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IgorC
post Nov 26 2012, 16:02
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It depens on and is up to You.

P.S. And True VBR has no advantage over Constrained one. This word "true" leads to misleading beleif that it's somehow better.
It's just a word. Both True and Constrained VBR are on par.

This post has been edited by IgorC: Nov 26 2012, 16:18
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eahm
post Nov 26 2012, 16:10
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Actually, I wanted to ask bout that yesterday. Are there documents about True VBR?

I did many test and I am perfectly fine with TVBR Q63.
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