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Absolute best AAC quality with qaac

I'm sure I'm not the first one asking this, but I could not find a definitve answer.

My car stereo only plays mp3 and aac. So flac in the car is sadly not an option.
But I want to get as close to that as possible. Size is not an issue.
I do not care about "audible difference" or something.
Even if you can't hear a difference there technically is more potential in higher bitrates or different algorithms.

I use foobar2000 to transcode my flacs to aac, so forgive me if I don't know the exact corresponding command line parameters.

I have the following options:
- VBR Q 127 : 320 kbps
- Constrained VBR 512 kbps
- ABR 512 kbps
- CBR 512 kbps

Should I just go with CBR 512? Is CBR 512 the absolute maximum AAC can do? Like 320 CBR mp3?
Or is it possible to get even closer to "lossless" with VBR, CVBR or ABR?

I am looking forward to being enlightened. Thanks
Regards

 

Re: Absolute best AAC quality with qaac

Reply #1
I bet that you won't recognize any difference between CBR 512 and VBR Q127 unless you have a high end setup in the car, and you highly probably won't even notice a difference between VBR @Q100. That's just a placebo feeling.
I would suggest to use anything above ~192kbps and you will be safe.

Re: Absolute best AAC quality with qaac

Reply #2
Even if you can't hear a difference there technically is more potential in higher bitrates or different algorithms.
No there isn't.

Re: Absolute best AAC quality with qaac

Reply #3
You are wasting your time. At these bitrates any differences will be inaudible... particular when listening in a car. Just pick the highest VBR setting if that makes you happy and focus on things that actually matter, like listening.

Re: Absolute best AAC quality with qaac

Reply #4
If your trying to achieve lossless then..

Re: Absolute best AAC quality with qaac

Reply #5
Quote
But I want to get as close to that as possible. Size is not an issue.
I do not care about "audible difference" or something.
Even if you can't hear a difference there technically is more potential in higher bitrates or different algorithms.
That doesn't make sense.  AAC is lossy and every single sample will be changed no matter what the setting. 

If the compression is transparent (sounds identical to the original) you can't get any "closer" the original.

Maybe  you could make the spectrum look like the original or make some mathematical analysis that's closer to the original "on paper", but you could end-up making it sound worse.   With lossy compression the ONLY important measure of quality is how it sounds.    The thing that makes AAC & MP3 so good is the psychoacoustic modeling (they are based on human perception of sound).    The compression algorithms that don't take human perception into account don't work as well.

     


Re: Absolute best AAC quality with qaac

Reply #6
It makes sense. OP says AAC / MP3 don't scale to lossless - that is true. Also OP probably wants 1 library : AAC or MP3 that plays anywhere. In this case overcoding ( 224.;.512k) gives headroom for rare problems and transcoding . This is proven and the spectrum can matter, even though lossless is prefered but to many it means multi libraries.

The other scenario is one may want to mainly deal in lossy mode, while maintaining an offline lossless archive. In the case the lossy is the daily workhorse. Should something happen to the lossless archive / hardware, the overcoded lossy provides a [near-lossless] fallback of sorts.
wavpack 4.8 -b4hx4c

Re: Absolute best AAC quality with qaac

Reply #7
[near-lossless] fallback of sorts.

There's no such thing. A lossless archive is for transcoding, remixing, production or (re-)mastering. A high quality lossy encoding is no replacement in any of these scenarios.

In any case where you actually need lossless I can't see a lossy copy as a viable alternative, no matter what quality settings it has. I can only think of scenarios where you don't actually need lossless.

Re: Absolute best AAC quality with qaac

Reply #8
I understand what you want, even though it's probably overkill. But in a way it gives some sort of "personal" insurance.

If you will be using qaac and encoding stereo 44.1 kHz. I don't think you can go higher than 320 kbps.
Code: [Select]
>qaac64.exe --formats
LC 44100Hz Stereo -- 64,72,80,96,112,128,144,160,192,224,256,288,320

The last public AAC listening test @ 96 kbps (July 2011) on this site says:
Quote
Quicktime CVBR ~> TVBR ~>Fraunhofer > CT > Nero

Assuming that order holds true throughout the bitrate range, just pick the first one. It may vary well be possible that a codec that is bad at 96 kbps is actually the best one at 320 kbps, but that would require more testing.

And assuming higher bitrate is always better quality, you'd pick the highest option. Note that is probably overkill by a lot, especially considering how bad of a listening environment a car can be because of all the external noise.

So you are probably looking at something like:
Code: [Select]
qaac -v320 

But in order to get an optimal bitrate value, you'd have to test them yourself, and I'm sure this is what you don't want to dedicate time to. Personally I use 128 kbps. Apple's "iTunes Plus" preset uses 256 kbps. And other users can suggest other values.

Re: Absolute best AAC quality with qaac

Reply #9
Quote
But I want to get as close to that as possible. Size is not an issue.
I do not care about "audible difference" or something.
Even if you can't hear a difference there technically is more potential in higher bitrates or different algorithms.
That doesn't make sense.  AAC is lossy and every single sample will be changed no matter what the setting. 

If the compression is transparent (sounds identical to the original) you can't get any "closer" the original.

Maybe  you could make the spectrum look like the original or make some mathematical analysis that's closer to the original "on paper", but you could end-up making it sound worse.   With lossy compression the ONLY important measure of quality is how it sounds.    The thing that makes AAC & MP3 so good is the psychoacoustic modeling (they are based on human perception of sound).    The compression algorithms that don't take human perception into account don't work as well.

     



Overcoding in AAC / MP3  = getting a better spectrum AND subjective quality [if one can hear] at the expense of disc space. The psymodel use less aggressive parameters [psymodel is *still* used + less lowpass, less mid/side, less noise shaping] so approaching closer to lossless coding and near-lossless. So saying you 'can't get closer to the original' is untrue.  AAC 512 / MP3 320 are the settings that correspond closest to FLAC.
wavpack 4.8 -b4hx4c

Re: Absolute best AAC quality with qaac

Reply #10
[near-lossless] fallback of sorts.

There's no such thing. A lossless archive is for transcoding, remixing, production or (re-)mastering. A high quality lossy encoding is no replacement in any of these scenarios.

In any case where you actually need lossless I can't see a lossy copy as a viable alternative, no matter what quality settings it has. I can only think of scenarios where you don't actually need lossless. So back to the original question: YES the top AAC / MP3 settings are closest to FLAC.

That is a matter of opinion . There's exists plenty of 'near-lossless'  scenarios on google with data compression although it is loosely defined. HA members can't simply decide it doesn't exist.
wavpack 4.8 -b4hx4c

Re: Absolute best AAC quality with qaac

Reply #11
thanks for all your replies, I think I'll stick with "VBR Q 127" for now

Re: Absolute best AAC quality with qaac

Reply #12
While your free to do whatever you want, I think q127 (i.e. 320kbps) is a total waste of space and is pretty much pointless to use as there is no efficiency at all at that point. I would not use any higher than what iTunes uses which is 256kbps CVBR, which is already a bit overkill.

I think the following is a pretty good guideline when it comes to AAC (with qaac with Foobar2000)...

-If your really paranoid about sound quality (which seems to be the case with the OP) = CVBR @ 256kbps. I think this is what iTunes uses and this is already more than really needed.
-If your largely concerned with sound quality but have even the slightest concern for efficiency = q91 (192kbps) TOPS.
-If your concerned with sound quality and efficiency, it's likely you will prefer one of the following... 96kbps/128kbps/160kbps as that seems to be what the clear majority prefer around here is one of those three settings based on what I have observed with polls etc. like you can go lower than 96kbps but your gambling on sound quality and higher than 160kbps and efficiency is mostly shot.

like many around here, I suggest you use 128kbps(q64) as at that rate it's not likely your going to notice any sound quality drops when playing it on a typical sound system etc and it's still very efficient. basically it's the sweet spot when it comes to AAC as one could not claim much either way of that in terms of the sweet spot simply because either sound quality would start to take a hit or efficiency would go out the window. hence, the 96kbps/128kbps/160kbps options are about the only ones people could choose from in terms of 'sweet spot' in my opinion.
For music (especially on-the-go)...
-I suggest Opus @ 96kbps (or... 64kbps minimum, 128kbps maximum). *preferred choice*
-I suggest AAC(Apple) @ 96kbps (q45 TVBR) or 128kbps (q64 TVBR). *secondary choice*
-I use Foobar2000 (/w Encoders Pack etc) to convert FLAC to Opus/AAC(Apple).

Re: Absolute best AAC quality with qaac

Reply #13
I understand that there is probably no noticeable difference between anything >256 kbps, but why would I ever go below the maximum bitrate when space is not an issue? I'd gain no advantages by doing so, just potential, on rare occasions, disadvantages (depending on ears, complexity of music, output device, probably never noticeable). but again, space is not an issue. it's not the year 1997. I'd gladly blow the files up to 4 times the size just to be "not lossy" and would still have much space left.

I did some more testing, the Foobar2000 setting "CBR 512" only processes exact 320 kbps files. (which is a little misleading imho)
My average bitrate for "CVBR 512" is around 352 kbps, "VBR Q 127" around 346 kbps, which is why I'm going with "CVBR 512" now, since the car stereo does not support any lossless formats (not even wav/pcm)

Re: Absolute best AAC quality with qaac

Reply #14
On car stereo, I'd go as low as 128

Re: Absolute best AAC quality with qaac

Reply #15
@Aldem

Quote
On car stereo, I'd go as low as 128

While that's a safe choice I doubt I would complain @ 96kbps AAC for a typical car stereo. although lower than that and your gambling as it seems 96kbps is sort of considered THE general safe minimum around here for AAC given listening tests etc.

I think it's plausible most people (if not a high percentage) would not find a problem with AAC @ 96kbps on a typical car stereo. like if you just encoded some music @ 96kbps and had some random friends come in your car and listen to it I would not expect any of them to notice it, at all.

p.s. on the extreme side of things, I would say 64kbps is THE very lowest I would go with music in general for AAC(AAC-LC). but this would be only in cases were one was really hard up for storage space and wanted a bunch of songs on the device. hell, I would not be surprised if 64kbps would be passable on a car stereo to where many would not even notice it because the core overall sound is not obviously bad at that point, especially on decent speakers, although any lower things really take a hit quickly.
For music (especially on-the-go)...
-I suggest Opus @ 96kbps (or... 64kbps minimum, 128kbps maximum). *preferred choice*
-I suggest AAC(Apple) @ 96kbps (q45 TVBR) or 128kbps (q64 TVBR). *secondary choice*
-I use Foobar2000 (/w Encoders Pack etc) to convert FLAC to Opus/AAC(Apple).

 
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