Nero HE aac plugin 5.1 encoding.

[Andrey]

I 've tried to encode DVD ac3 5.1 track to HE aac 5.1 through a Nero aac plugin using OAGMachine and found interesting problem.
I 've wanted bitrate to be around 128 Kbit, so, I 've selected constant bitrate 128, quality High, and HE AAC profile.
The stream was encoded in LC profile.
Ops.
I've tried once again. The same result.
Then I tried to select an options not via OAGMachine + Nero dialog, but through Nero plugin configuration.
So, when I selected parameters above, press Ok, Close and close Nero and when open it again LC profile was selected.
It seems that Nero automatically uses LC profile, when encoding at CBR 128.
So, the question is: how to set a target bitstream of 5.1 HE AAC encoding to overall 128 Kbit ?
Any ideas ?

Thanks in advance !
Edited:
May be I should set bitrate to 64 Kbit ?
Encoding is slow (more than 8 hours) so if anybody has exact answer it
will help a lot :)

[Tuning]

Originally posted by Andrey
It seems that Nero automatically uses LC profile, when encoding at CBR 128.


HE-AAC was meant to be used for lowbitrate encoding. Thus obviously larger bitrates uses LC by default. In presets dropdown menu its already shown that up to 80k will use HE-AAC. If you still want CBR HE-AAC and at high bitrates then use CBR profile @80k.

Also note that there is no exact CBR encoding in Nero aac plugin. It always changes +/- 5kbps. More than that there is no reliable equation to calculate what bitrate to be used to get overall 128kbps. I would suggest using VBR @ streaming profile.

*EDIT* < SEE TIKI4'S ADVICE BELOW >

[Andrey]

Thats all understandable and I know it.
But note that 21 Kbit per channel isn't a high bitrate encoding ! :)
(128/6 ~ 21)

[Tuning]

Originally posted by Andrey
(128/6 ~ 21)

If you already know, why you asked LC is used instead on HE ?? (Joking...) ;).

I think division you described is not correct. Bcoz AAC uses special methods like M/S matrixing and intensity stereo etc.(Just like joint stereo in mp3).
So internally bits are saved according to these alorithms. So correctly this will not be the actual bitdistribution per channel.
btw, i don't know how to deduce a equation corresponding to your request. Sorry.:(. I'm too looking for similar equation, but nero plugins bitrates are changing rapidly with every version...so what i do is first encode HE-AAC 5.1 and considering its file size bitrate to video is decided.

[mikeson]

@Andrey:
But note that 21 Kbit per channel isn't a high bitrate encoding ! (128/6 ~ 21)
You are wrong. Look at Ivan's explanation here (http://www.hydrogenaudio.org/index.php?showtopic=15883&).

[Tuning]

Originally posted by mikeson
You are wrong. Look at Ivan's explanation here (http://www.hydrogenaudio.org/index.php?showtopic=15883&).
Thanks mikeson for this link.

For HE-AAC to get quality of 128kbps mp3, 24kbps is used per channel by formulae: 2 x 48 + 32 (because of coupling channels need less) = 128 Kb/s
That is each stereo pair uses 48kbps and centre uses 32kbps.

But how could I select 128kbps HE-AAC, bcoz at this bitrate nero aac API uses LC for encoding!. And possibly 80K is the maximum CBR bitrate for HE-AAC. Getting confused now :confused:.

[mikeson]

Tuning:

Just have a look at bitrate of 5.1 AC3 encoded with HE-AAC profile and Internet or Streaming preset. Bitrate would vary from 170kbps to 240kbps (I'm talking about 5.1 AAC, not downmixed to 2.0).

But I agree, a little bit more tweaking possibilities in Nero AAC encoder configuration would be nice. ;)

Maximum bitrate settings for CBR HE-AAC is 96kbps

[Andrey]

>>You are wrong. Look at Ivan's explanation here.
Yep. I knew it. That's why I gonna test it for myself.
BTW: 64 Kbit/ch in mp3 encoding (and the same stands for 32/ch for SBR technology and 24/ch, if we agree that aac 96 ~= 128 mp3) is not high bitrate encoding too :):)
Simply, that is a simple measure of bitrate = think as it is encoded not in Joint mode, but in Double/Multi channel. And just to remeber, that perceptual quality of Joint stereo/multi ch mode usually is a bit better...

>>But how could I select 128kbps HE-AAC, bcoz at this bitrate nero >>aac API uses LC for encoding!. And possibly 80K is the maximum CBR >>bitrate for HE-AAC. Getting confused now

Thanks, Tuning, you got the point! :)
I agree - "confused" that was just what I feel when I found it :)

Thanks all for the answers !
As I see, problem exists and there is no solution, period...
That's bad, because now I must first compress sound, and only then - video, because when using presets bitrate is undefined...
Edited:
[BTW, if I select a very low bitrate profile, like Tape for example, will some LP filters be applied automatically ?
If no, it could be a solution, not good one, but working...]

[mikeson]

@Andrey:
BTW: 64 Kbit/ch in mp3 encoding (and the same stands for 32/ch for SBR technology and 24/ch, if we agree that aac 96 ~= 128 mp3) is not high bitrate encoding too
No, it isn't high bitrate encoding, but HE-AAC profile is not aimed at high bitrates but at the low ones. If you want high bitrates, simply use AAC-LC.

[Andrey]

:D
Agreed.
I simply became mad when reading one of the first replies: :)
>>HE-AAC was meant to be used for lowbitrate encoding. Thus obviously larger bitrates uses LC by default.
So, if 128 Kbit for 6 channels is a large bitrate I will eat my hat :)
That was the point :)
Thus is strange, that Nero codec is build in such a way...
BTW, do Nero Recode 2 share such a "feature" ?

[mikeson]

@Andrey:
do Nero Recode 2 share such a "feature" ?
Yes, Nero Recode 2 uses the same Nero AAC encoder.

BTW as I've posted above, when you use Internet or Streaming presets together with HE-AAC profile while transcoding 5.1 AC3 to 5.1 AAC, you will achieve bitrate range from 170kbps to 240kbps (of course, it may vary and depends on transcoding content).

[Tuning]

Originally posted by mikeson
Tuning:
Just have a look at bitrate of 5.1 AC3 encoded with HE-AAC profile and Internet or Streaming preset. Bitrate would vary from 170kbps to 240kbps (I'm talking about 5.1 AAC, not downmixed to 2.0).
But I agree, a little bit more tweaking possibilities in Nero AAC encoder configuration would be nice. ;)
Maximum bitrate settings for CBR HE-AAC is 96kbps

Thanks mikeson for clearing out. Guess what i was looking then: global preset settings; which showed 80k as maximum HE-AAC preset in CBR. Then I tested to verify, it gave HE-AAC upto 96kbps. ;)

Btw, I always use radio:low preset for HE-AAC instead of internet:streaming.

*EDIT* < SEE TIKI4'S ADVICE BELOW >

With newer version of nero aac, the maximum attainable bitrate has reached around 200k.(even for He-AAC). Thus with radio:low profile you will get bitrates around 100-160kbps, which I think is optimum for 5.1 HE-AAC. Getting lesser size and good quality.

@Andrey
if I select a very low bitrate profile, like Tape for example, will some LP filters be applied automatically ?
This is disastrous selection because nero aac downsamples to 32khz or below at this preset. Instead use internet:streaming VBR.

Your only way is to calculate audio file size first and then decide what video bitrate is to be used.

Happy encoding!

@Tiki4

What strategy do you use ?:D

[tiki4]

Hi, someone was asking for me...

Well, I didn't read the whole thread, but if I remember correctly Ivan said one can use HE-AAC up to 128 kBit/s for a six channel source. I think I was able to produce such a file, but I just can't remember how at the moment. My guess would be that one has to decode the AC3 to AIFF and load this one into Nero. I'll try that later (I don't have Nero on my Linux machine :D ).

@Tuning: Usually I use HE-AAC with 'streaming' preset for 5.1. I found lower bitrates are sounding terrible to me.

tiki4

[Tuning]

Originally posted by tiki4
@Tuning: Usually I use HE-AAC with 'streaming' preset for 5.1. I found lower bitrates are sounding terrible to me.


In respect of tiki4's advice, I would use streaming:medium profile from now on. :) I think radio:low is good for stereo sources. And foobar reproduces good sound at this bitrate. And ofcourse, size is very very small.:p

What bitrate do you use for music, tiki4? :D :rolleyes:

[tiki4]

Haha, for music: mppenc --quality 6 --xlevel (Musepack).

tiki4

Btw: my preference of 'streaming' wasn't meant as advice. It's just what I like and not based on any real testing.

[mikeson]

@Tuning:
I think radio:low is good for stereo sources
It is not important on what source is it used on (5.1 or 2.0) because when 2.0 is source, bitrate of Streaming preset would be around 80-90kbps (it depends on kind of source material, of course), but when the same preset is used on 5.1 material, bitrate would be roughly around 200kbps.

[Tuning]

Originally posted by mikeson
@Tuning:

It is not important on what source is it used on (5.1 or 2.0) because when 2.0 is source, bitrate of Streaming preset would be around 80-90kbps (it depends on kind of source material, of course), but when the same preset is used on 5.1 material, bitrate would be roughly around 200kbps.
Thanks mikeson, this is a new news to me. I never looked in to what bitrate it will use after encoding. Only looked the size. Thanks for this info.

btw, I have a doubt, how the encoder determines the source, bcoz AFAIK, nero uses only one pass.