Skip to main content ↑ ↓

Notice

Please note that most of the software linked on this forum is likely to be safe to use. If you are unsure, feel free to ask in the relevant topics, or send a private message to an administrator or moderator. To help curb the problems of false positives, or in the event that you do find actual malware, you can contribute through the article linked here.
Topic: AAC Conversion settings? (Read 14611 times) previous topic - next topic
0 Members and 1 Guest are viewing this topic.

AAC Conversion settings?

(Sorry if this is in the wrong place)

Hello,

Needed to sort out my music collection, so decided on musicbee, with converting my FLACs to AAC for use with iTunes syncing to my iPhone.

Question is, I'm using the qaac encoder as I read it is generally regarded to be the best (as it directly uses Apple's own). Loading the codec in musicbee and enabling AAC, I see it provides default values. (such as -q 0.45 -if - -of [outputfile]) Will these also work well for qaac? I should be fine with those conversions?

Finally, I'm not exactly sure how the quality translates fro those 0-2 figures. I have been used to 256kbps AAC being used as standard for a while, so what would that translate to with the 0-2 system?

(Feel free to correct me if I don't need it, I'm an avid FLAC audiophile, so I just want the best quality/size ratio for when converting to AAC to put on my iphone, I'm a bit green around the edges when it comes to lossy formats!)

AAC Conversion settings?

Reply #1 –
Quote from: nostos156 on
I see it provides default values. (such as -q 0.45 -if - -of [outputfile]) Will these also work well for qaac? I should be fine with those conversions?

I'm sure those are n`t for qaac but nero. So you have to use different settings.

Quote from: nostos156 on
Finally, I'm not exactly sure how the quality translates fro those 0-2 figures. I have been used to 256kbps AAC being used as standard for a while, so what would that translate to with the 0-2 system?

If I remember good U need not set anything with quality as it already defaults to 2 which is highest.

To get audio up to pair to iTunes use constant bitrate near 256kbps (or use variable bitrate around 256k for better result)

AAC Conversion settings?

Reply #2 –
-q 0.45 is a typical Nero setting, corresponding to about 146 kbps.  The -q option for qaac exists but doesn't do the same thing.  Instead it can be thought of as controlling the level of compression without affecting the audio in any way.  It can be set to 0, 1, or 2, and is usually set to 2.  The only advantage of lower numbers is faster encoding at the expense of a slightly larger output file.

For qaac, use the -V (true VBR and the recommended choice), -v (constrained VBR), -a (adaptive VBR), or -c (CBR) options to control the bitrate of the output file.  Note that the value for "true VBR" mode is not a bitrate at all, but just a number between 0 and 127.  Usually a tvbr setting around 100 is good.

AAC Conversion settings?

Reply #3 –
Yeah vbr at 100 is completely transparent for me, but if size doesn't too much matter then using something between 109-118 gives something like iTunes releases (which is already a bit overkill IMO). Depends on how trained ears and earphones nostos156 uses.
Anyway for portable use (outdoors) using audiophile audio parameters is mostly kind of wasting memory card 

AAC Conversion settings?

Reply #4 –
Well at home I use an NAD D 3020 amp with Philips X1 headphones (and an ex user of HD650s) so you can say I like my audio.

Okay, so just to make sure I don't mess this up as this is all new to me:



What would be the qaac equivalents to those command line parameters? And yeah, I won't need audiophile parameters, just those that pretty much match the ones itunes use (or ideally, what is best for quality/size ratio, I figure you guys will know this better than I do)

AAC Conversion settings?

Reply #5 –
For output pretty much like iTunes use
Code: [Select]
--cbr 256 --ignorelength -o [outputfile] -

For best quality try true VBR at 100 like suggested above
Code: [Select]
--tvbr 100 --ignorelength -o [outputfile] -

As best is always individual, try with 109 or 118 if you hear any artifacts

AAC Conversion settings?

Reply #6 –
Ah, thanks for that. I'll definitely try true VBR if that's even better quality than the standard. What does true VBR do exactly that makes it better? Kinda curious as I'm guessing cbr locks it at 256kbits?

AAC Conversion settings?

Reply #7 –
Quote from: nostos156 on
What does true VBR do exactly that makes it better? Kinda curious as I'm guessing cbr locks it at 256kbits?

Yes exactly, it uses constant bandwith amount for each block while VBR is more flexible (using as much bitrate as needed to preserve constant quality depending on each block complexity)

AAC Conversion settings?

Reply #8 –
Quote from: Anakunda on
Quote from: nostos156 on
What does true VBR do exactly that makes it better? Kinda curious as I'm guessing cbr locks it at 256kbits?

Yes exactly, it uses constant bandwith amount for each block while VBR is more flexible (using as much bitrate as needed to preserve constant quality depending on each block complexity)


So in essence, it retains the same quality as 256kbits, but having a much smaller file size due to it being flexible with how much compression it needs to apply? Sounds neat. Why doesn't iTunes use that?

AAC Conversion settings?

Reply #9 –
"True" VBR is VBR  The bitrate can vary.  As much or as little as the encode algorithm thinks best to represent each audio frame at the best audio quality, given the -V setting.

AAC has a bunch of other modes, all of which have variable bitrates to some extent, but with limits on the variation.  Unless it is important to you to produce highly uniform bitrates or file sizes then the -V (capital V) setting should be your first choice.

AAC "CBR" is a not entirely constant bitrate, but the variation is strongly limited.  The audio quality of a CBR file the same size as a VBR one is pretty much always a lot worse.  You may have to go 50% larger (higher bitrate) to achieve transparency with the CBR mode.  There is really very little reason to use it.  iTunes uses either the constrained or adaptive VBR modes for business reasons, to limit the amount of variation in file sizes and bitrates, and presumably because CBR is so poor in comparison, or perhaps again for business reasons because CBR is perceived to be a lower quality choice.

AAC Conversion settings?

Reply #10 –
Ah, I was under the impression iTunes just used 256kpbs CBR or something akin to that, but I guess not. Well, thanks for that, it has been very helpful. Now to go and try those VBR 100 settings posted earlier.

AAC Conversion settings?

Reply #11 –
iTunes used to use a true CBR back in the old old days of MP3.  I don't know if its AAC non-VBR setting was ever a true CBR, but for the last few years it has been ABR, as in qaac -a.  I'm pretty sure it still is although I don't use it.  ABR (average or adaptive?) files always come out pretty close to the chosen bitrate overall, but can vary internally.

AAC Conversion settings?

Reply #12 –
Ah. The only disadvantage I'm reading of True VBR (although it seems like all ABRs can be affected) is some music players can get confused and screw up the track times? That still an issue?

AAC Conversion settings?

Reply #13 –
Quote from: nostos156 on
Ah. The only disadvantage I'm reading of True VBR (although it seems like all ABRs can be affected) is some music players can get confused and screw up the track times? That still an issue?

It only applies to MP3 but not to AAC.
AAC, unlike MP3, usually uses proper container format (MP4/M4A) in which every AAC frame is indexed and  random accessible. Things like that cannot happen regardless of CBR/VBR.

In case of VBR MP3, accurate seeking of it requires special care such as frame scan in the background thread, which I believe several players such as fb2k does but usually most implementation does not.

AAC Conversion settings?

Reply #14 –
In my experience, even foobar2000 has trouble seeking within long VBR MP3 files. If you seek to the end of the file, the counter won't match the playback position anymore.

AAC Conversion settings?

Reply #15 –
Hi, just thought I'd come back and say that I have these settings:



But when I try to convert a sample track it just fails, saying no output file was processed, and to check the encoding command line parameters which may be incorrect.

AAC Conversion settings?

Reply #16 –
nostos156, make sure you use the profile for that only you have filled in the params and flll in the full pathname to encoder location for case it's not accessible withinn %path%

AAC Conversion settings?

Reply #17 –
Made sure of that, and tried putting the full pathname in too, as well as changing the parameters a little bit (as I was told there was a slight error)

Quote
--tvbr 110 --ignorelength - -o [outputfile]


However, it still fails?

AAC Conversion settings?

Reply #18 –
That's really strange. For curiosity installed portable musicbee and was able to convert a flas dir to AAC in desired profile




AAC Conversion settings?

Reply #19 –
It's alright, I fixed it.

Turns out I forgot to install the C++ 2013 redistribute, as I was on a fresh windows 8.1 installation.

AAC Conversion settings?

Reply #20 –
New question, for curiosity sake:

What's the real world difference between tvbr 100 and 110? Or technical difference other than 110 being higher quality?

AAC Conversion settings?

Reply #21 –
Quote from: nostos156 on
New question, for curiosity sake:

What's the real world difference between tvbr 100 and 110? Or technical difference other than 110 being higher quality?

The true VBR setting is just a number between 0 and 127.  Higher is better quality, aka higher overall bitrate and larger files.  I have no clue how they do this internally.  As a very rough rule of thumb, a given quality setting will give you something like twice that number as an overall bitrate, maybe a little more.  I guess it is that way since the bitrate is entirely unconstrained and so specifying the -tvbr value as a bitrate would be meaningless.  -tvbr 100 in one file might give a bitrate of 160kbps, while it might give 256kbps on another file.  Theoretically the audio quality of both files should be similar.  On the same file, 110 will give you more or less 10% higher bitrate than 100, but don't expect it to be exact.

AAC Conversion settings?

Reply #22 –
Apple's VBR scale seems to be pretty much arbitrary; it goes from 0 - 127, but there are only 15 steps, with all the numbers in between being useless. I've often wondered if qaac would be less confusing to new users if nu774 would just use a VBR quality scale from 0 - 14 and hide Apple's nonsensical numbers, but since the purpose of qaac seems to be just to expose all the switches in Apple's library, I guess he doesn't want to do that.

AAC Conversion settings?

Reply #23 –
TVBR 100 and 110 are different (the resulting file size/ bitrate should be different), but 109 and 110 are not. For the latter case, same quality scale will be internally used.
You can see the actual quality scale written in the tool tag (which may not be exactly the same as what you set via command line switch).
 

AAC Conversion settings?

Reply #24 –
The quality measurement between various scale values impacts also lowpass (or highpass or whatever the higher cutoff is named  ) frequency. I think that scales 118 and 127 don't cut off at all while 91 has it at 19.5kHz and 100 at 20.6kHz