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Lossy Audio Compression => AAC => AAC - Tech => Topic started by: rupeshforu3 on 2017-07-05 18:08:40

Title: meaning of technical terms in Nero aac and fdk aac
Post by: rupeshforu3 on 2017-07-05 18:08:40
Hi I am Rupesh from India and I have some music files and I want to convert to other file format which have reduced file size at no quality loss atleast minimum.

I have done some experiments and found that aac is the best codec which produces m4a files or mp4 files.

I have tried three tools or software ie., lamexp,foobar and dbpoweramp and in these I have found the terms lc, he aac, he2 aac, he aac below 56 kbps, he 2 aac below 96 kbps of which last two are from dbpoweramp.

Can you suggest what is the meaning and difference between lc, he and he2. Which is the best recommend for optimum sound quality and also which is the best recommended for lower file size. For some files I have used 48 kbps and for some I have used 64 kbps and for some I have used 80 kbps. Coming to lc, he,he v2 I have confused.

Please suggest which one to select ie., lc,he,he v2 for bitrates 48 kbps to 96 kbps so that I will re convert source files to produce m4a files with optimum sound quality at lowest file sizes.

Regards,
Rupesh.
Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: saratoga on 2017-07-05 18:57:25
Usually LC is used at most higher bitrates, while HE trades off sound quality for higher compression and so is used at very low bitrates. 

The Nero encoder will automatically decide the correct format.  Unless you have hardware that does not support HE, you should probably just let the encoder decide. 
Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: pdq on 2017-07-05 19:21:33
The Nero encoder will automatically decide the correct format...
based on the selected bitrate.
Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: rupeshforu3 on 2017-07-06 05:27:16
If Nero automatically detects correct format what about fdk.

Please provide a detailed description of lc,he,he v2 or otherwise a web page link.
Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: saratoga on 2017-07-06 06:05:53
http://wiki.hydrogenaud.io/index.php?title=AAC
Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: lvqcl on 2017-07-06 07:31:35
also
https://wiki.multimedia.cx/index.php/Advanced_Audio_Coding
https://en.wikipedia.org/wiki/Advanced_Audio_Coding
https://en.wikipedia.org/wiki/High-Efficiency_Advanced_Audio_Coding
Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: rizukitomi on 2017-08-09 18:35:39
If Nero automatically detects correct format what about fdk.

AFAIK, FDKAAC does not automatically change profile, the same as QAAC, so you have to choose it yourself...
Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: Makaki on 2017-08-09 22:35:56
This image sums it up:
https://en.wikipedia.org/wiki/File:HE-AAC_and_HE-AAC_v2.svg

LC-AAC (Low Complexity): is pretty much standard AAC, supported by any player that supports AAC.

HE-AAC (High-Efficiency): the first version of HE adds SBR (spectral band replication). Lower bitrates will sound better, typically recommended under 80kbps. Depending on the song there will be a bitrate where LC vs HE would be a tie. Under that bitrate HE would win and over that bitrate LC would be enough and more compatible with players.

HE-AAC v2: adds PS (parametric stereo) to enhance the compression efficiency of stereo signals. Not all encoders support this. AND Not all players support this. In theory, most players would still play the file but at a reduced quality.

Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: rupeshforu3 on 2017-11-24 11:00:01
Upon experimenting I have noticed various pros and cons in each method and I am going to share them with you.

One interesting fact is that files converted with foobar and Nero aac encoder is producing worst quality and even with greater file size. I have a directory of 960 mp3 files with 4.7 GB. First I converted with foobar and Nero aac encoder with 48 kbps vbr and it converted those files to m4a of size 1.7gb. Then I have converted using db power amp with fdk aac and 64 kbps vbr and he v2 aac and this time the file size is 1.6 GB. Finally I have converted using db power amp with 64 kbps vbr and lc aac this time the converted files size is, 1.3 GB. The audio quality of the files converted in the last step is acceptable and the files converted using foobar is not at all good.

Upon analyzing the above scenario can I say that foobar converter is not good and db power amp is best than foobar. Can I say that Nero aac produces worst quality audio files.

Suppose I want to convert using fdk aac with 48 kbps vbr can you suggest which of the above setting's to use and suppose I want to convert using fdk aac with 64 kbps vbr can you suggest which of the above setting's to use.


May I know which codec among m4a, opus is best for lowest file size.

Regards,
Rupesh.
Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: lithopsian on 2017-11-24 14:16:20
I'll just get my popcorn and watch the show  ;D
Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: saratoga on 2017-11-24 15:38:54
aac or opus will both work well. The above links is provide more details about specific encoders and settings. 
Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: rupeshforu3 on 2017-11-24 17:26:40
Is Nero aac inferior than fdk aac. Which of opus, aac(m4a) produce smallest file size for music.
Title: Re: meaning of technical terms in Nero aac and fdk aac
Post by: polemon on 2017-11-24 22:46:57
Is Nero aac inferior than fdk aac. Which of opus, aac(m4a) produce smallest file size for music.
When it comes to file sizes, it's impossible to answer. You'd have to create a test sample, such that it is transparent for your setup, use-case, etc.
Then, you can have a look at the file size. On average, file sizes between Apple AAC and Opus seem to be similar for a stereo track. At least in my cases.

As for Nero AAC vs. Fdk AAC, here are some listening tests by other users: http://wiki.hydrogenaud.io/index.php?title=Hydrogenaudio_Listening_Tests

I'm not sure whether Nero AAC still sees maintenance, though. However, I'd simply make a short ABX test yourself if I were you, etc.

I'd give yourself a margin, when it comes to size differences, though. When the difference in file sizes is in the single digits percent wise, I'd deem them equal.

Also note, that it's down to the settings, you can actually make very large files, which sound horrible, by using a rather unfortunate combination of settings. So be wary of that, should you try to tweak them, etc.
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