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Topic: How good is AAC VBR in iTunes 5? (Read 100890 times) previous topic - next topic
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How good is AAC VBR in iTunes 5?

Reply #25 –
For sure... mainly on the shuffle which skips like F*** on both nero and faac VBR files at higher bit rates.

How good is AAC VBR in iTunes 5?

Reply #26 –
Keep in mind how they implemented 'VBR' on their MP3 encoder. Although they've already deviated away with settings being ABR instead of 'minimum bitrate', they haven't really shown an interest in true-VBR before. Also as much as I like Apple, with the encoder and iTunes there to support iPod sales, the general public happy with 128 kbps, and 'storage space' calculated off 128 kbps AAC, there may not be an incentive to have a VBR that would potentially run above. Hope I'm wrong though.

Curious in the future to see a test how the increased ABR range affects quality.

How good is AAC VBR in iTunes 5?

Reply #27 –
Most people are happy with 128K CBR, but I for one was surprised that Apple introduced their own lossless codec. So it seems that they are aware that some people are interested in quality much above 128K lossy.

How good is AAC VBR in iTunes 5?

Reply #28 –
I am hoping the reason for their "VBR" keeping keeping file size close to CBR is that they will soon be offering a choice of bitrate for downloads on the iTunes music store.
This could also be the reason why you can only use VBR to encode certain bitrates.
I know it's probably a bit of a stretch but I would like this to be the reason.

How good is AAC VBR in iTunes 5?

Reply #29 –
I think it's because the hardware of the Shuffle and Nano isn't up dealing with proper VBR.  ABR is the only way they can ensure that iTunes encoded AAC will play on every player at every bit rate.

How good is AAC VBR in iTunes 5?

Reply #30 –
Quote
I think it's because the hardware of the Shuffle and Nano isn't up dealing with proper VBR.  ABR is the only way they can ensure that iTunes encoded AAC will play on every player at every bit rate.
[a href="index.php?act=findpost&pid=326812"][{POST_SNAPBACK}][/a]


I don't believe this. You can have VBR with an upper bitrate cap, to start with. Secondly,  the AAC standard gives guarantees about max bitrates and so, which a compatible decoder should handle.

If their decoder is really limited in this way, you should be able to make a fully standard compliant CBR AAC file of (for example) 32kbps that skips like hell on Apple devices.

How good is AAC VBR in iTunes 5?

Reply #31 –
This is totally conjecture and speculation - but I did a 'strings' on the iTunes 5.0 binary and it specifically makes reference to protected lossless files in this list:

plist/dict/AudioCodecs:dict/AIFF:dict/
plist/dict/AudioCodecs:dict/AIFF:dict/MinimumSampleRate:integer/
plist/dict/AudioCodecs:dict/AIFF:dict/MaximumSampleRate:integer/
plist/dict/AudioCodecs:dict/MP3:dict/
plist/dict/AudioCodecs:dict/MP3:dict/MinimumSampleRate:integer/
plist/dict/AudioCodecs:dict/MP3:dict/MaximumSampleRate:integer/
plist/dict/AudioCodecs:dict/MP3:dict/MinimumBitRate:integer/
plist/dict/AudioCodecs:dict/MP3:dict/MaximumBitRate:integer/
plist/dict/AudioCodecs:dict/MP3:dict/VariableBitRate:true/
plist/dict/AudioCodecs:dict/MP3:dict/VariableBitRate:false/
plist/dict/AudioCodecs:dict/WAV:dict/
plist/dict/AudioCodecs:dict/WAV:dict/MinimumSampleRate:integer/
plist/dict/AudioCodecs:dict/WAV:dict/MaximumSampleRate:integer/
plist/dict/AudioCodecs:dict/AAC:dict/
plist/dict/AudioCodecs:dict/AAC:dict/MinimumSampleRate:integer/
plist/dict/AudioCodecs:dict/AAC:dict/MaximumSampleRate:integer/
plist/dict/AudioCodecs:dict/AAC:dict/MinimumBitRate:integer/
plist/dict/AudioCodecs:dict/AAC:dict/MaximumBitRate:integer/
plist/dict/AudioCodecs:dict/AAC:dict/AppleDRM:true/
plist/dict/AudioCodecs:dict/AAC:dict/AppleDRM:false/
plist/dict/AudioCodecs:dict/AAC:dict/AudioBooks:true/
plist/dict/AudioCodecs:dict/AAC:dict/AudioBooks:false/
plist/dict/AudioCodecs:dict/AppleLossless:dict/
plist/dict/AudioCodecs:dict/AppleLossless:dict/MinimumSampleRate:integer/
plist/dict/AudioCodecs:dict/AppleLossless:dict/MaximumSampleRate:integer/
plist/dict/AudioCodecs:dict/AppleLossless:dict/AppleDRM:true/
plist/dict/AudioCodecs:dict/AppleLossless:dict/AppleDRM:false/
plist/dict/AudioCodecs:dict/Audible:dict/Type2:true/
plist/dict/AudioCodecs:dict/Audible:dict/Type2:false/
plist/dict/AudioCodecs:dict/Audible:dict/Type3:true/
plist/dict/AudioCodecs:dict/Audible:dict/Type3:false/
plist/dict/AudioCodecs:dict/Audible:dict/Type4:true/
plist/dict/AudioCodecs:dict/Audible:dict/Type4:false/

We might see lossless on iTMS after all...

How good is AAC VBR in iTunes 5?

Reply #32 –
Quote
We might see lossless on iTMS after all...
[a href="index.php?act=findpost&pid=326828"][{POST_SNAPBACK}][/a]

I love my Karma, but I'd give it up in a second if the 60GB iPod Photo could do a few of it's tricks (namely, gapless playback). I don't really care for DRM, but if the entire iTMS library became available in Apples lossless format, I think I could be persuaded to buy into it after giving it much serious thought, and only if the price was right of course. It's mainly the conveniance of being able to download single tracks instead of buying entire albums just for one or two songs that appeals to me I think.

How good is AAC VBR in iTunes 5?

Reply #33 –
Quote
This is totally conjecture and speculation - but I did a 'strings' on the iTunes 5.0 binary and it specifically makes reference to protected lossless files in this list:

We might see lossless on iTMS after all...
[a href="index.php?act=findpost&pid=326828"][{POST_SNAPBACK}][/a]


Did you check whether this wasn't on the previous version too?

I mean, I'm sure Apple can (technically) sell lossless songs. Wheter they're allowed to is another manner.

Imagine what happens if the DRM gets broken again.

How good is AAC VBR in iTunes 5?

Reply #34 –
Quote
Quote
This is totally conjecture and speculation - but I did a 'strings' on the iTunes 5.0 binary and it specifically makes reference to protected lossless files in this list:

We might see lossless on iTMS after all...
[a href="index.php?act=findpost&pid=326828"][{POST_SNAPBACK}][/a]


Did you check whether this wasn't on the previous version too?

I mean, I'm sure Apple can (technically) sell lossless songs. Wheter they're allowed to is another manner.

Imagine what happens if the DRM gets broken again.
[a href="index.php?act=findpost&pid=326830"][{POST_SNAPBACK}][/a]


I don't think any particular version number makes a difference (iTunes has had .ogg icons in the package ever since I can remember and still no support except via 3rd party quicktime components) but more that they at least have the infrastructure and foundation to support it. Everyone thought it was weird that lossless files used a .m4a extension. I'm unsure whether they're in an MP4 style container or whether they're a completely custom header & fileformat and just happened to be named that way arbitrarily - but if it's the former, then it's clear they made it that way specifically so their current fairplay implementation would work with it easily. That's how  I see it anyway. Either way it's nice to know they've thought about it and haven't written the concept off completely. (Not that I could use it anyway being in Australia....still waiting...)

How good is AAC VBR in iTunes 5?

Reply #35 –
Quote
Quote
I think it's because the hardware of the Shuffle and Nano isn't up dealing with proper VBR.  ABR is the only way they can ensure that iTunes encoded AAC will play on every player at every bit rate.
[a href="index.php?act=findpost&pid=326812"][{POST_SNAPBACK}][/a]


I don't believe this. You can have VBR with an upper bitrate cap, to start with. Secondly,  the AAC standard gives guarantees about max bitrates and so, which a compatible decoder should handle.

If their decoder is really limited in this way, you should be able to make a fully standard compliant CBR AAC file of (for example) 32kbps that skips like hell on Apple devices.
[a href="index.php?act=findpost&pid=326815"][{POST_SNAPBACK}][/a]

Mmm... well I have tried both Nero VBR and FAAC VBR on the shuffle, and I get skips, whereas CBR I do not.  I'm also noticing tiny skips on the Nano, with Nero VBR, FAAC VBR and iTunes 5 VBR (only at 256k, 192k is OK).  I'm only reporting my personal experience here.

How good is AAC VBR in iTunes 5?

Reply #36 –
Quote
I'm also noticing tiny skips on the Nano, with Nero VBR, FAAC VBR and iTunes 5 VBR
[a href="index.php?act=findpost&pid=326853"][{POST_SNAPBACK}][/a]


Well, I guess that settles the question  Their AAC decoder is junk.

CBR can't protect you from this because there is a bitrate reservoir system similar to MP3, although you're of course less likely to have problem cases.

How good is AAC VBR in iTunes 5?

Reply #37 –
Thanks Garf, at least I know I am not going insane.  At lower bit rates all the problems disappear on both shuffle and nano, but at lower bit rates I can hear that I'm listening to a lossy format so it kind of destroys the objective.

I have actually reverted to LAME 3.97a11 -V 1 --vbr-new for these players and have no problems, although can still ABX.  For my iPod photo I am still using FAAC at q 250 with no TNS, but eagerly looking forward to Nero 7.

I should add that both Nero VBR and FAAC VBR play seamlessly on the iPod photo, so maybe they just haven't adapted their AAC decoder sufficiently for the flash-based models.

How good is AAC VBR in iTunes 5?

Reply #38 –
Quote
They may be afraid of skipping on the Ipods.
[a href="index.php?act=findpost&pid=326615"][{POST_SNAPBACK}][/a]

good one 
--alt-presets are there for a reason! These other switches DO NOT work better than it, trust me on this.
LAME + Joint Stereo doesn't destroy 'Stereo'

How good is AAC VBR in iTunes 5?

Reply #39 –
so have people come to the conclusion that itunes 5 aac vbr is useless?  in that case, i won't use it.

How good is AAC VBR in iTunes 5?

Reply #40 –
Quote
so have people come to the conclusion that itunes 5 aac vbr is useless?  in that case, i won't use it.
[a href="index.php?act=findpost&pid=327084"][{POST_SNAPBACK}][/a]

I think we've come to the conlcusion that iTunes VBR AAC is actually some kind of iTunes ABR AAC. We still don't have concrete avidence that it is worse or better than standard iTunes CBR AAC.
Still, remember this: VBR>ABR>CBR.
we was young an' full of beans

How good is AAC VBR in iTunes 5?

Reply #41 –
Quote
so have people come to the conclusion that itunes 5 aac vbr is useless?  in that case, i won't use it.
[a href="index.php?act=findpost&pid=327084"][{POST_SNAPBACK}][/a]


Why not try using it yourself? If you like it use it, if not then don't.

How good is AAC VBR in iTunes 5?

Reply #42 –
Results of a little testing I did tonight:

First I tried to find a hard-to-encode track.  The highest bitrate (losslessly compressed) song I had was Küss Mich (Fellfrosch) by Rammstein.  For comparison purposes, lame 3.97b1 --preset standard results in a bitrate of 222kbps.

Converted to AAC with iTunes 5.0.0.35 for Windows:
Küss Mich (Fellfrosch) 160 CBR.m4a = 4,254,203 bytes
Küss Mich (Fellfrosch) 160 VBR.m4a = 4,496,400 bytes

So iTunes will kick up the bitrate for a difficult track, but not by very much at all.

Next I made an easy-to-encode track, a 44.1khz, 16-bit, stereo 40Hz sine wave, peaking at -12db.  Lame 3.97b1 --ps gives 34kbps.

Converted to AAC with iTunes 5.0.0.35 for Windows:
40,180 160 CBR.m4a = 1,120,641 bytes
40,180 160 VBR.m4a = 1,120,477 bytes

Not saving many bits, is it?

EDIT: I realized something about my results makes no sense.. a true 160 CBR encode of a 3 minute file should be much larger.. lame 3.97b1 --preset cbr 160 gives a file size of 3,601,763 bytes for the 3 min. sine wave.  So it seems iTunes uses some type of variable bit rate even when it's supposed to be in CBR mode?

How good is AAC VBR in iTunes 5?

Reply #43 –
Quote
So it seems iTunes uses some type of variable bit rate even when it's supposed to be in CBR mode?
[a href="index.php?act=findpost&pid=327151"][{POST_SNAPBACK}][/a]


You're probably right. I don't think iTunes ever uses CBR for AAC. I remember in earlier versions before the VBR option, the bitrate would fluctuate a bit, more like ABR. Try playing one of the "CBR" files in foobar and watch the bitrate.

How good is AAC VBR in iTunes 5?

Reply #44 –
Quote
...
The highest bitrate (losslessly compressed) song I had was Küss Mich (Fellfrosch) by Rammstein.  For comparison purposes, lame 3.97b1 --preset standard results in a bitrate of 222kbps.
...
Next I made an easy-to-encode track, a 44.1khz, 16-bit, stereo 40Hz sine wave, peaking at -12db.  Lame 3.97b1 --ps gives 34kbps.
...
Just curious, what were the files sizes in each case when you used LAME.

How good is AAC VBR in iTunes 5?

Reply #45 –
Quote
Quote
...
The highest bitrate (losslessly compressed) song I had was Küss Mich (Fellfrosch) by Rammstein.  For comparison purposes, lame 3.97b1 --preset standard results in a bitrate of 222kbps.
...
Next I made an easy-to-encode track, a 44.1khz, 16-bit, stereo 40Hz sine wave, peaking at -12db.  Lame 3.97b1 --ps gives 34kbps.
...
Just curious, what were the files sizes in each case when you used LAME.
[a href="index.php?act=findpost&pid=327162"][{POST_SNAPBACK}][/a]


For the --preset standard encodes?  Küss Mich was 5,867,549 bytes and the 3 min. 40Hz sine was 756,810 bytes.

How good is AAC VBR in iTunes 5?

Reply #46 –
Instead of all these bitrate tests which are a bit, well, lame - why not do some listening tests?

How good is AAC VBR in iTunes 5?

Reply #47 –
Some of the converted albums (vbr-modus) appear with 191-197kBit/s in iTunes ... others show 192kBit/s 

How good is AAC VBR in iTunes 5?

Reply #48 –
Quote
So it seems iTunes uses some type of variable bit rate even when it's supposed to be in CBR mode?
The bit reservoir can cause slight bitrate fluctuation in CBR mode.

How good is AAC VBR in iTunes 5?

Reply #49 –
Quote
Instead of all these bitrate tests which are a bit, well, lame - why not do some listening tests?

I second the notion.  I'm curious if anybody has found for example "I needed iTunes to encode at X kbps before but now I can use Y kbps VBR mode and get transparency".