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View Full Version : Converting MP3 to AAC - no size reduction?




jl24
Dec 22, 2006, 02:20 PM
I am getting an iPod nano for Christmas and I'm trying to trim my music library down. Therefore I've found most of my songs are MPEG audio files 128kbps (I'm guessing that means MP3), and I converted a few to AAC 128kbps. However there is no size change. I thought AAC files were smaller. Am I doing something wrong?



balamw
Dec 22, 2006, 02:21 PM
I am getting an iPod nano for Christmas and I'm trying to trim my music library down. Therefore I've found most of my songs are MPEG audio files 128kbps (I'm guessing that means MP3), and I converted a few to AAC 128kbps. However there is no size change. I thought AAC files were smaller. Am I doing something wrong?

Same bitrate & time = same size.

AAC sounds better (to some users) at 128 kbps than 192 kpbs MP3.

B

killmoms
Dec 22, 2006, 02:45 PM
Think of bitrate like miles per hour. Is a BMW going 50mph faster than a Ford going 50mph? Of course not.

Similarly, 128kbps is always 128kbps, no matter what technology is being used to compress something down to that rate.

balamw
Dec 22, 2006, 02:50 PM
Good analogy.

Similarly, 128kbps is always 128kbps, no matter what technology is being used to compress something down to that rate.
Just like the Ford & BMW analogy you might enjoy one more than the other even though strictly from the point of view of performance(size) they are the same.

B

gnasher729
Dec 22, 2006, 03:16 PM
I am getting an iPod nano for Christmas and I'm trying to trim my music library down. Therefore I've found most of my songs are MPEG audio files 128kbps (I'm guessing that means MP3), and I converted a few to AAC 128kbps. However there is no size change. I thought AAC files were smaller. Am I doing something wrong?

Yes. 128kbps is the size (it is Kilobit per second, so 128 kilobit per second at 8 bit per byte is 16 Kilobyte per second, close to one Megabyte per minute of music). 128kbps is always the same size.

When you rip music from a CD, you can compress it. The more you compress it (fewer kbps), the more quality you lose. The difference between MP3 and AAC is that AAC loses less quality. 128kbps AAC ripped from CD sounds better than 128kpbs MP3 from the same CD. Or if you want the same quality, 128kbps AAC has about the same quality as 192kbps MP3.

However, once you have MP3 files, you have already lost quality. Converting it to AAC will not improve it at all. You should either leave your MP3s as they are, or rip your CDs again, this time as AAC.

dukebound85
Dec 22, 2006, 03:32 PM
yes the above poster is right. i wouldnt convert mp3 to aac if you are concerned about quality. heck even if you were to encode at say 356kbs in aac from a 128kbs mp3, the aac qould still have worse quality but alot more size. soley due to the fact that you are compressing and already compressed file. think of it like making a tape the making a copy of the tape and then a copy of the copy.......the quality decreases each time