AAC + iTunes

who knows? mp3 is the audio file format at the moment. it'll take a lot of time for aac to become a new standard, if ever. but having the option available in itunes would be a good step nonetheless.
 
Apple at least said that AAC has a big potential to replace MP3, mainly because of the sound quality, which is much higher than on MP3 at the same bitrates. (This is from the QuickTime 6 preview site.)

So I guess we'll see an iTunes 3 this summer with AAC support, but of course without leaving MP3 behind. Maybe they'll make AAC standard. They like having new standards first nowadays, as they don't invent them any longer. :p (Where's my GigaWire?)
 
actualy... i would like to see a variety of new codec's, on my pc... the best codec is not aac, aac is good, definatly better then mp3, but ogg by vorbis is by far the best. i encoded some cd's at 350 some kbps and the bigest file was about 2.5 megs.... that astoundingly small file at almost unnessasary bit rate.

i would like to see itunes 3, with every codec possible to encode, decode, and play.
 
Originally posted by satanicpoptart
i encoded some cd's at 350 some kbps and the bigest file was about 2.5 megs.... that astoundingly small file at almost unnessasary bit rate.
Click to expand...

350 some kbps? 2.5 meg size file?

let's see... *takes calculator*

with the numbers given, that file was about 58 seconds in length.

350 some... let's say 352.

352kbps = 44 kilobytes per second
2.5 megabytes = 2560 kilobytes
2560 kilobytes / 44 kilobytes per second = 58.18 seconds
 
what would it take for the ipod to support aac? a firmware update? a new ipod?
 
That would be so sweet. People would ask me "Is that an MP3 player?" and I would say " No, it's an AAC player" and just walk away.:D
 
just tell me this: will i be able to fit more AAC files at the same quality as mp3s on my ipod?
that would be GREAT
 
Originally posted by MacPain


350 some kbps? 2.5 meg size file?

let's see... *takes calculator*

with the numbers given, that file was about 58 seconds in length.

350 some... let's say 352.

352kbps = 44 kilobytes per second
2.5 megabytes = 2560 kilobytes
2560 kilobytes / 44 kilobytes per second = 58.18 seconds
Click to expand...

i dont think it works that way...

if it worked that way then if i encoded an aac file at 128 and a mp3 at 128 they would be the same size.

but that dosnt happen the aac is about 1/3 the size of the mp3 at the same kbps.
 
Originally posted by satanicpoptart


i dont think it works that way...

if it worked that way then if i encoded an aac file at 128 and a mp3 at 128 they would be the same size.

but that dosnt happen the aac is about 1/3 the size of the mp3 at the same kbps.
Click to expand...

actually, it should work that way.

look, when you encode a piece of music at 128kbps that'll mean that each second of the track will "weigh" 16 kilobytes (which are 128 kilobits). at 192kbps each second is 24 kilobytes in size, at 256kpbs it's 32 kilobytes.

sorry, it's the maths. 128kpbs will mean 16 kilobytes per second, no matter what format.
 
The difference in size is based on the compression of the data.. not because of the kbps. If this was true than the same should be noted between other streaming media. Compare a real audio file with a mp3 file of similar kbps.

I don't have much knowledge on this and so that everyone can get the right information, I'll just shut my trap and point to their site.

http://www.aac-audio.com/ :eek: :eek: :rolleyes:
 
Originally posted by MacPain

sorry, it's the maths. 128kpbs will mean 16 kilobytes per second, no matter what format.
Click to expand...

You two are mixing file sizes and bit rates.

The bit rate refers to the rate the information is sent speakers. As you pointed out by your calculations, this is a lot of data for audio. If there were no compression of the data the audio files would be huge. Art and science are applied to make the file sizes as small as possible without giving up too much on sound quality. Thus we have MP3 files which compress a CD (roughly 600MB) into about a 60MB file.
 
I don't know for sure, but I think MacPain is right. 128kbps means that the file requires 128,000 bits for every second of audio. That's 16,000 bytes for every second. 160kbps means 160,000 bits (or 20,000 bytes) of hard drive space for every second of audio. Shouldn't matter what format, codec or whatever, "the kbps don't lie."

For a 3 minute 128kbps song:
3 minutes = 180 seconds
128kbps = 128,000 bits per second = 16,000 bytes per second
180seconds * 16,000 bytes/second = 2,880,000 bytes = 2.8MB.
Which is about what you would expect for a 3-minute 128kbps mp3.

After reading Apple's spiel on AAC I was under the impression that AAC gives you smaller file sizes because its advanced compression techniques result in you being able to record at lower bitrates and still have an audio file that sounds as good as an mp3 that was recorded at a higher bitrate.

So says Apple: (http://www.apple.com/mpeg4/aac/)
"AAC compressed audio at 128 kbps (stereo) has been judged by expert listeners to be 'indistinguishable' from the original uncompressed audio source.
"AAC compressed audio at 96 kbps generally exceeded the quality of MP3 compressed audio at 128 kbps. AAC at 128 kbps provides significantly superior performance than does MP3 at 128 kbps.
"AAC was the only Internet audio codec evaluated in the range “Excellent” at 64 kbps for all of the audio items tested in EBU listening tests."

So, extrapolating and guessing quite roughly, all those people that say that a 128kbps mp3 is just dandy should think that a 64kbps aac song is just as dandy.
Those people who think they need 160 or 192kbps mp3's should think a 96kbps aac audio file does just as good of a job.
And all those audiophiles that pine for 320kbps mp3's should fall in love with 128kbps aac's which, according to apple, are “'indistinguishable' from the original uncompressed audio source" and are less than half the size of a 320kbps mp3.

So, approximately, if you stick with whatever sound-quality you are used to, using AAC could cut the space your audio files take up in half. That would give you 2,000 songs on a 5GB iPod and 4,000 songs on a 10GB iPod.

How does that 'sound'?
 
bit rates determine overall file sizes
Click to expand...

That is not totally true. Bit rates determine that amount of information that needs to be stored. The compression algorithm will then take that information and try to compress it in size according to its rules. This means that the file size is a function of two factors (at least): bit rate and compression. Two music tracks of the same length and bit rate may have different sizes because the compression algorithm may be able to compress one more than the other. Correspondingly the same track with the same bit rate compressed using different techniques will likely be of a different size.

However:

After reading Apple's spiel on AAC I was under the impression that AAC gives you smaller file sizes because its advanced compression techniques result in you being able to record at lower bitrates and still have an audio file that sounds as good as an mp3 that was recorded at a higher bitrate.
Click to expand...

If this is true (and I have no reason to doubt it) then the bitrate quoted is post compression and so the file size is only really dependant upon bit rates.

An analogy can be made with GIF and JPEG. Both are different compression routines and will give different sizes of files for the same Bitmap.

The final file size will also depend on the file system used, though that is a smaller effect (hopefully).

R.
 
Bitrate for streaming media is always post-compression--it would be meaningless otherwise (raw bitrate when ripping CD is always 44100 * 16 ( * 2 for stereo))
 
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