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Doubting profile, LC vs HEv2
OSTIN130
post Jan 6 2009, 23:22
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Hi,
I was just starting ripping CDs(AudioCD) when I wondered what profile was better. I've read about AAC-LC /HE / HE v2 but the thing is tha HEv2 is 2.5MB and LC is 8MB and I can't find the difference with my computer speakers (some Dell 5.1) and my ears smile.gif. I encode the with Dbpoeramp and the Nero Digital plugin at VBR 0.65 (similar to 256kbps) Why do I get a 2.5MB (at 85kbps) HEv2???
One more thing! What's the bit rate I should use to have a good quality? iTunes is using 256CBR AAC so I was going to use 256VBR AAC... Is that enough or too little?
On dbpoweramp I can choose between Nero AAC and m4a Nero AAC... but they seem to use the same encoder... which is better?

Thanks!
(I'm spanish so if you don't understand something, just tell me and I'll try to explain)

This post has been edited by OSTIN130: Jan 6 2009, 23:23
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saratoga
post Jan 7 2009, 01:19
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QUOTE (OSTIN130 @ Jan 6 2009, 17:22) *
Hi,
I was just starting ripping CDs(AudioCD) when I wondered what profile was better. I've read about AAC-LC /HE / HE v2 but the thing is tha HEv2 is 2.5MB and LC is 8MB and I can't find the difference with my computer speakers (some Dell 5.1) and my ears smile.gif. I encode the with Dbpoeramp and the Nero Digital plugin at VBR 0.65 (similar to 256kbps) Why do I get a 2.5MB (at 85kbps) HEv2???


AAC-HE is for low bitrates, LC is for high. If you use HE, you're going to be using low bitrates.

QUOTE (OSTIN130 @ Jan 6 2009, 17:22) *
One more thing! What's the bit rate I should use to have a good quality? iTunes is using 256CBR AAC so I was going to use 256VBR AAC... Is that enough or too little?


If 85kbps sounds good, 256kbps is probably too much. I'd probably use a little less and AAC-LC due to poor compatibility with HE.
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kornchild2002
post Jan 7 2009, 03:13
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As Mike said, I would stick with LC-AAC. LC-AAC should be used for bitrates of around 96kbps and higher. Additionally, more devices are compatible with LC-AAC than HE-AAC. You should start off using Nero's AAC encoder at around 96kbps VBR and conduct blind ABX tests. Past listening tests have shown that most people are perfectly fine with 128kbps LC-AAC in terms of transparency and that 256kbps CBR/VBR AAC is overkill. In other words, most people don't need such a high bitrate to achieve perceived "CD quality."

So stick with LC-AAC if you have AAC compatible devices such as an iPod, Zen, Zune, etc. Don't use HE-AAC as the files won't fully work on those devices.

There isn't a difference between Nero AAC and m4a Nero AAC. Both use the same Nero AAC encoder but one method produces AAC files with file names of *.mp4 (replace the * with whatever). The m4a Nero AAC method produces songs with file names of *.m4a, this makes them more compatible with other devices and software. Apple established this file name standard back when their third generation iPods were launched (2003).

They broke away from using the generic mp4 extension. You see, mp4 files can house audio, video, or both at the same time. This could mean that a user has all these mp4 files on their hard drive but don't know what they are. Apple chose m4a to represent audio, hence the a at the end. m4p represented iTunes Store purchased songs (not anymore though), m4v is for videos, and m4b is for books.
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OSTIN130
post Jan 7 2009, 14:43
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OK so... LC gives more quility than HEv2? (I couldn't hear any differences...)
I don't have compatibility problems on my device but I still don't understand why Apple is using 256CBR AAC files (do they use low complexity) if normal people can't perceive the difference
Thanks to all of you


P.S: Mike... low bitrate means less qualiity?
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IgorC
post Jan 7 2009, 16:25
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HE-AAC V2 is only usefull up to ~40 kbit/s. HE-AAC V2 is already worse (or no quality gain in better case) than HE-AAC V1 at 48 kbit/s.

HE-AAC V1 is only usefull up to ~80-85 kbit/s. HE-AAC V1 is already worse than LC at 90 kbit/s.

Nero will choose most suitable profile automaticly:
HE-AAC V2 up to 36-40 kbit/s
HE-AAC V1 up to 80-85 kbit/s
LC-AAC >85 kbit/s.

The user has only specify -q parametr. Nothing else.

This post has been edited by IgorC: Jan 7 2009, 16:26
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senab
post Jan 7 2009, 16:49
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If you're using Nero, and you don't have the compatibility problems of HE-AAC then do not force a profile and simply specify a quality value. Nero has been tuned to use PS and SBR (the things that are used on top of LC-AAC for HE-AAC v1 & 2) for the correct bitrates already.

In my personal opinion, although the quality of HE-AAC is superb for the given bitrate, SBR adds its own artifacts which annoy me after continuous listening. I personally use iTunes AAC 128k VBR and am very happy with it.

This post has been edited by senab: Jan 7 2009, 16:52


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muaddib
post Jan 8 2009, 12:39
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QUOTE (IgorC @ Jan 7 2009, 16:25) *
HE-AAC V2 is only usefull up to ~40 kbit/s. HE-AAC V2 is already worse (or no quality gain in better case) than HE-AAC V1 at 48 kbit/s.
HE-AAC V1 is only usefull up to ~80-85 kbit/s. HE-AAC V1 is already worse than LC at 90 kbit/s.

"On most samples for most users" must be added! Otherwise more people will start discussions on HA how they think that LC or HE is better at some bitrate because they hear it on some samples. smile.gif
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Goran Tomas
post Jan 8 2009, 17:17
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QUOTE (OSTIN130 @ Jan 7 2009, 14:43) *
I don't have compatibility problems on my device but I still don't understand why Apple is using 256CBR AAC files (do they use low complexity) if normal people can't perceive the difference


Who said they can't?

What one can hear or not will depend on numerous factors, such as the state of person's hearing, the "criticalness" of coded audio material, the quality and type of sound system the listener is listening on (especially speakers/headphones) and how critical (trained/sensitive) the listener is.

That being said, 256 kbps AAC is high enough you probably won't be able to hear any artifacts at all. I'm actually pleasantly surprised to hear they decide to go with the bitrate as high as that. Previously I've written iTunes off because the bitrate was not high enough for me, but I'll have to reconsider them now.

I would also advise you to go with LC AAC. For enjoyable listening experience I personally don't like the SBR artifacts of HE-AAC and to me they are quite obvious at any bitrate. With AAC I wouldn't go below 128 kbps bitrate, but it's up to you to decide what quality/size compromise is acceptable to you...


Regrads,
Goran Tomas
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kornchild2002
post Jan 8 2009, 21:45
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QUOTE (OSTIN130 @ Jan 7 2009, 06:43) *
I don't have compatibility problems on my device but I still don't understand why Apple is using 256CBR AAC files (do they use low complexity) if normal people can't perceive the difference


You are having compatibility issues though. You see, programs like iTunes and devices such as all iPods, Zunes, AAC compatible Zens, etc. aren't fully compatible with HE and HE2 AAC files. These players will only decode back the LC portions of HE (and HE2) files. So a 64kbps HE-AAC file will actually have worse sound quality than a 64kbps LC-AAC file when being played back on iPods. That is why you really need to stick with LC-AAC if you want full iTunes and iPod compatibility. I hope that wasn't too confusing. Just know that iTunes and iPods won't properly playback HE (and HE2) AAC files.

I am not sure why Apple decided to use such a high bitrate. My guess is that they wanted to play on the general idea that people have: more is better. It is sad as iLounge has many people who go there saying that they rip all their CDs at 256kbps thinking they need such a high bitrate and then refuse to take any blind ABX tests. They think "Apple uses it, I will use it even though I don't need it." I personally don't benefit from the increase in bitrate as Lame at -V 3 produces transparent results for me (and iTunes AAC at 160kbps VBR). Just know that you don't have to use such a high bitrate setting simply because Apple does with their music store. I continually shop on Amazon's mp3 store as they sell DRM-free mp3 files. The files are encoded at either 256kbps CBR (with some form of the FhG mp3 encoder), -V 0 (with Lame 3.97), or abr 256kbps (with Lame 3.98.2). I didn't go through and re-encode my lossless files to any of those settings simply because Amazon uses those standards.
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OSTIN130
post Jan 9 2009, 18:53
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I don't have issues with HEv2!!!!!!
And what's the difference between itunes aac and nero aac? is the result different

thanks to everybody
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IgorC
post Jan 9 2009, 19:25
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You should perform your own blind test as it's matter of personal hearing perception.
I did my own last time ago http://www.hydrogenaudio.org/forums/index....c=66949&hl=
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