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Topic: AAC: There are some detectable difference from CD? (Read 7971 times) previous topic - next topic
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AAC: There are some detectable difference from CD?

Hi to all,

I'm near to 200 original CD and I want to digitalize them with iTunes.

In future I will buy music from iTunes.

There are detectable difference from CD when use an AAC on an HIFI system?

I will hear my music not with the headphone.

I ask that, because I want to start ripping my CD, but firstly I want to chose the better format.

AAC or AIFF?

On iTunes there is only the AAC version to buy?


Thanks

AAC: There are some detectable difference from CD?

Reply #2 –
The last AAC listening test at 128kbps, performed about 6 years ago, showed that trained listeners can occasionally tell the difference on some difficult samples, but that overall, many samples were transparent to a lot of listeners. The encoders have advanced since then, so it would be even more difficult now.

Differences are usually easier to detect using headphones than with speakers.

As for "better format", that is a pretty meaningless question.

AAC: There are some detectable difference from CD?

Reply #3 –
Probably, if you can abx the difference between lossless *wav files from cd* to lossy *aac codec*.

However, in regards to the itunes store, they use 256 constrained vbr aac.The thing I like about some of the itune store music is the volume of the files go well together with their peak values in replaygain compared to conventional cd's *meaning the loudness on the files aren't as harsh or brickwalled as the cd's normal values*.I however, do not know or understand why this is, but I'm not complaining.Also, at around that bitrate you probably won't be able to notice the difference, however, just to be safe, with dbpoweramp they have the ability to allow you to rip and encode using codecs like mp3 and nero aac at over 400kbps.

Rip your cd's in wav using eac or dbpoweramp, and go rip the same in itunes using the preset itunes plus *its availible in itunes, and is the exact preset they encode music in the store at*, and then abx the two to see if you notice any differences.If you are able to, just keep increasing the bitrate of what you encode until you are no longer able to.

In my personal experience, 256 vbr aac would be overkill, as I tried to abx mp3 v2 lame and flac, and couldn't, but then again I don't listen on professional equipment, just my ipod or computer speakers.

AAC: There are some detectable difference from CD?

Reply #4 –
Quote from: Mix3dmessagez on
The thing I like about some of the itune store music is the volume of the files go well together with their peak values in replaygain compared to conventional cd's *meaning the loudness on the files aren't as harsh or brickwalled as the cd's normal values*.I however, do not know or understand why this is, but I'm not complaining.
Do you have any examples: titles, something anyone else could check to verify that iTunes Plus files are anything other than CD rips?

AAC: There are some detectable difference from CD?

Reply #5 –
Quote from: dv1989 on
Quote from: Mix3dmessagez on
The thing I like about some of the itune store music is the volume of the files go well together with their peak values in replaygain compared to conventional cd's *meaning the loudness on the files aren't as harsh or brickwalled as the cd's normal values*.I however, do not know or understand why this is, but I'm not complaining.
Do you have any examples: titles, something anyone else could check to verify that iTunes Plus files are anything other than CD rips?


I'm sorry,  this was not the case and I was wrong.What I will say however is that itune files are perfect and contain no audible cd errors or anything, the music sounds completely clean as if it were lifted straight from the source recording *imo*.

AAC: There are some detectable difference from CD?

Reply #6 –
Generally, iTunes seems to offer excellent quality as far as I can tell, even during the 128kbps copy-protected AAC era (before iTunes+). My only qualm is occasionally I'd rather have an older issue of the CD than they ripped (e.g. a Pink Floyd track where the loudness war had muted the drums too much for my taste, so I didn't get beyond previewing the track in the iTunes Store).

If you're ripping your own CDs via iTunes you can also choose a lossless format and convert to lossy for the version you sync to your phone/iPod or iPad. As there's no error detection in iTunes, so glitches may sneak through.

There are two approaches I'd recommend:

1. Rip whole CDs using iTunes, saving files as Lossless, then...
1a: Then use CUETools (on a Windows PC) to check all the ripped albums against the AccurateRip database. If any tracks are inaccurate, CUETools may be able to error-correct popular pressings automatically (using CTDB) or failing that you can re-rip that CD using a 'secure' CD ripper - see below for suggestions.
If you use approach 1, I'd recommend you try it out on a couple of CDs before ripping 200 just to check that CUETools can identify the AccurateRip DiscID from the iTunes rips. If it can't I'd really, recommend using option 2:

2. Rip all your CDs using one of the secure rippers that verifies your rip against the AccurateRip database, such as:
  dBpowerAmp
  CUEripper (in CUETools)
  Exact Audio Copy
  Foobar2000 CD ripper
  or if you have a Mac, try XLD to rip your files.

Some of those in option 2 can save directly as Apple Lossless (ALAC), while some (e.g. dBpowerAMP and CueTools) can convert more mainstream/open lossless formats like FLAC into ALAC.

[edit: option 1, advised to check that CUETools can correctly identify the disc before ripping 200 CDs]
Dynamic – the artist formerly known as DickD
 

AAC: There are some detectable difference from CD?

Reply #7 –
I don't know anything about itunes and what it will or won't do, and chances are I never will, but....

If I were ripping all my CDs I'd use a program which can rip in secure mode. It's slower but it reads a section of the track, then reads it again to make sure it's getting the same data both times. I think if it doesn't get the same data it tries again until it's got two reads which are the same. Or there's a more secure mode which I think requires four identical reads but it's much slower.

I'd rip to a lossless format such as flac so I always have a lossless copy, then I'd convert the flac files to AAC. You can also run ReplayGain on the flac files and save the ReplayGain info as tags (it doesn't effect the actual data). Then when you convert to AAC you can apply the ReplayGain as you convert if you wish so each AAC file will have the same apparent loudness as the next. ReplayGain has two modes. Track gain which levels every song, or Album Gain which changes the volume of a group of songs by the same amount (so the relative volumes between songs from the same album will remain the same).

When converting to AAC you can use a quality setting. It's kind of like using the MP3 VBR V2 preset, except the quality setting works on a scale (Q0.05 to Q1.00). I think Q.50 is supposed to be transparent. It'll give you an average bitrate of around 175kbps.

For all of the above I'd use foobar2000. It'll rip in secure mode and convert to flac at the same time. If you have more than one CD drive it'll rip more than one CD at a time. It'll write tags to your ripped files (it can use an internet database for tagging) and it'll scan them using ReplyGain. It'll convert to AAC and it'll apply ReplayGain in the process if you wish it to.
To use foobar2000 for the job you'll need to download the flac and Nero AAC encoders yourself and foobar will just ask where they are the first time you try to convert. It has presets for converting to both flac and AAC. The AAC preset is already set to Q.50 but you can of course change it if you wish.