I have "Golden Ears" Which AAC VBR Bitrate is acceptable? Options

[KmanKaiser]

So, yes, I have the "golden ears" everyone refers too...

I can actually hear the difference between FLAC, and MP3 320 kbps

I can hear the difference between 1,536 Kbps DTS, 800 Kbps VBR AAC, and 384/640 Kbps AC3 when I watch films, and my equipment isn't very fancy either


I just finished transcoding my FLAC discography of Eminem to 128 Kbps VBR AAC

I am thinking of retranscoding (again, from flac) to 192 Kbps or 320 Kbps VBR AAC
but is it necessary? (this is going to be for playback from my ipod touch)

My FLAC files look something like this...
Format/Info : Free Lossless Audio Codec
Duration : 6mn 42s
Bit rate mode : Variable
Bit rate : 2 849 Kbps
Channel(s) : 2 channels
Sampling rate : 96.0 KHz
Bit depth : 24 bits
Stream size : 137 MiB (100%)

This post has been edited by KmanKaiser: Aug 29 2012, 09:37

[Kohlrabi]

I can hear the difference between 1,536 Kbps DTS, 800 Kbps VBR AAC, and 384/640 Kbps AC3 when I watch films, and my equipment isn't very fancy either

More often than not DTS and AC3 tracks on a movie medium are based on different masters, making them unsuitable for comparison.

I am thinking of retranscoding (again, from flac) to 192 Kbps or 320 Kbps VBR AAC
but is it necessary? (this is going to be for playback from my ipod touch)

Use ABX tests to determine your threshold for AAC encoding. There is no golden setting for everybody, especially not if you are able to routinely identify artifacts at high bitrates.

My FLAC files look something like this...
Format/Info : Free Lossless Audio Codec
Duration : 5mn 13s
Bit rate mode : Variable
Bit rate : 2 726 Kbps
Channel(s) : 2 channels
Sampling rate : 96.0 KHz
Bit depth : 24 bits

These files are based on DVD-A rips? If these are CD rips you should seek to replace them with proper CD rips.

This post has been edited by Kohlrabi: Aug 29 2012, 09:40

[KmanKaiser]

I have 2 of every album, one has these insane stats ^

and the other with these kind of stats

Format/Info : Free Lossless Audio Codec
Duration : 5mn 46s
Bit rate mode : Variable
Bit rate : 862 Kbps
Channel(s) : 2 channels
Sampling rate : 44.1 KHz
Bit depth : 16 bits
Stream size : 35.6 MiB (100%)

This post has been edited by db1989: Aug 29 2012, 10:48

Reason for edit: deleting pointless full quote of above post

[Kohlrabi]

So, one of them is (likely) a CD rip and the other is based off of some other source.

This post has been edited by Kohlrabi: Aug 29 2012, 09:50

[shadowking]

Do a proper abx test. Forget current trends, dont look at bitrates and spectrograms . Once things get difficult you stick with that setting or go *a little* higher - If 128k aac gives good results then: encode with 128..150..170 etc

[db1989]

So, yes, I have the "golden ears" everyone refers too...

I can actually hear the difference between FLAC, and MP3 320 kbps

I can hear the difference between 1,536 Kbps DTS, 800 Kbps VBR AAC, and 384/640 Kbps AC3 when I watch films, and my equipment isn't very fancy either

If you don’t have valid objective evidence to support these fanciful claims, in line with #8 of the terms of service to which you agreed during registration, your statements are unwelcome and your thread is at risk of being binned without notice.

[DVDdoug]

So, yes, I have the "golden ears" everyone refers too...

In that case, only YOU can determine what YOU can hear!

If you ears are really that good, or if you are "paranoid", or if you are simply not concerned with file size, just go-ahead use the best possible AAC setting and try not to worry about it. Or if you have the storage space, go with ALAC. (Your iPod won't play FLAC, but it should play ALAC.)

... and my equipment isn't very fancy either

You don't need high-end equipment to hear compression artifacts. If you hear artifacts on high-end equipment, you can probably hear them on an average system.

But, program material DOES make a difference. (Some songs are "easier" to compress than others.)

This post has been edited by DVDdoug: Aug 29 2012, 19:26

[eahm]

KmanKaiser, I thought I had golden ears as well (I was able to tell the difference between 320 CBR LAME and 320 CBR Fraunhofer with a 4 hour ABX test), until I started ABX everything and I didn't care anymore, ABX will destroy your ego.

I reconverted everything in FLAC for archival purposes and cared about size only for portable use, ending up using ~115 Kbps AAC True VBR for my iPhone and car.

Always, always ABX.

This post has been edited by eahm: Aug 29 2012, 19:39

[greynol]

I was able to tell the difference between 320 CBR LAME and 320 CBR Fraunhofer with a 4 hour ABX test

You mean this topic of yours that was binned because you failed to provide evidence in accordance with TOS #8?

This post has been edited by greynol: Aug 29 2012, 20:03

[db1989]

Moreover, comparing one lossy format to another (an apple to an orange) is pretty pointless. I might grant it a minimal amount of validity in cases where one absolutely cannot obtain a non-compressed version to use as a proper control—but, basically, no.

[greynol]

A passed ABX only guarantees that one of them is not transparent from the original source.

[db1989]

And if comparing two lossy encodings, it could be one or both, with a positive result indicating only that one sounds more lossy. Or something

[greynol]

Exactly.

[Porcus]

A passed ABX only guarantees that one of them is not transparent from the original source.

The more I think of that statement, the more interesting it gets (although I guess, not in practice, where I presume that the codecs would share some artifacts, making ABXing them harder, or at least no easier, than original-to-lossy).

But in principle, the artifacts could be disjoint, giving you “twice as many” artifacts to detect -- or even worse (though even less likely in practice), it could “double” an artifact -- say, one note getting a treble boost not noticeable until you compare to the other codec which has a treble cut on the same note; say +D to 0 is inaudible, -d to 0 is inaudible, +D to -d is.

Conditioned upon this being the situation (not too likely I'd say, but for the sake of the argument), claiming “one of them is not transparent” is the inference that “in this signal, D to 0 is audible or 0 to (-d) is audible” from the observation “in this signal, D to -d is audible”. Or, simplifying to absolute value terms, “max{D,d} is audible” from “D+d is audible”. What is the type I/type II trade-off, and how does that compare to the likely low N used in ABXing each to the original?

(In the more realistic case where artifacts are shared, the inference would be “in this signal, max{D,d} is audible” from “in this signal, |D-d| is audible”, and that is ... not too objectionable.)

[tycho]

Moreover, comparing one lossy format to another (an apple to an orange) is pretty pointless.

Comparing a lossy encoding from WAV with the same lossy encoding from e.g. lossyWAV is quite interesting IMO, (assuming lossyWAV from WAV is transparent). But strictly "comparing one lossy format to another" is rather pointless, agreed.

[Apesbrain]

[greynol]

But in principle, the artifacts could be disjoint, giving you “twice as many” artifacts to detect -- or even worse (though even less likely in practice), it could “double” an artifact -- say, one note getting a treble boost not noticeable until you compare to the other codec which has a treble cut on the same note; say +D to 0 is inaudible, -d to 0 is inaudible, +D to -d is.

You're absolutely right; I was wrong. Changes in EQ, level and stereo balance all fit this latter situation and are perfectly good candidates as ABX stimuli. I'm not sure I can come up with real-world examples that would fall under the former, though someone else might.

[DonP]

Being able to hear differences between lossless and lossy means that your hearing (and/or training) varies from the model used in compression. Your ears could be gold or tin!

Hypothetical example: the model assumes that a cannon shot in your left ear will mask a pin drop in your right ear. IF you are stone cold deaf in your left ear, then you will hear whether the pin drop is there, missing, or echoing. A person with full hearing wouldn't.