Lossless vs. AAC & burning questions

[DJ in TX]

So I am just getting into audio and home theater, and just purchased a set of bookshelves (Paradigm) and a receiver (Pioneer). My speakers should be delivered any day now, so I am very eager to get started.

In the mean time I am trying to fill in the many gaps of my knowledge, and the latest gap is related to MP3, AAC, AAC+, and Apple Lossless music formats.

If I understand correctly, MP3, AAC and AAC+ have audio bits removed for compression so that you can squeeze alot on your iPod, but the downside is that audio is then lower quality as some parts are missing. On an average system or in the car I shouldn't expect to notice a difference, but on higher end systems I might hear a difference depending on the recording. If any of this is wrong so far, just let me know.

My new Pioneer receiver boasts technology to improve playback of MP3s and other digital audio formats, but obviously it won't be as good as a lossless format. I am assuming there is no way to convert my iTunes library from AAC to lossless, as the music data in my tracks is gone. So this would mean re-ripping my library?

Also, if I use iTunes to burn an audio CD of random music from my library, since the source data is AAC and therefore missing info, will the Audio CD also be lower quality than the commercially available audio CD of this same band?

 

[lsiberian]

So I am just getting into audio and home theater, and just purchased a set of bookshelves (Paradigm) and a receiver (Pioneer). My speakers should be delivered any day now, so I am very eager to get started.

In the mean time I am trying to fill in the many gaps of my knowledge, and the latest gap is related to MP3, AAC, AAC+, and Apple Lossless music formats.

If I understand correctly, MP3, AAC and AAC+ have audio bits removed for compression so that you can squeeze alot on your iPod, but the downside is that audio is then lower quality as some parts are missing. On an average system or in the car I shouldn't expect to notice a difference, but on higher end systems I might hear a difference depending on the recording. If any of this is wrong so far, just let me know.

My new Pioneer receiver boasts technology to improve playback of MP3s and other digital audio formats, but obviously it won't be as good as a lossless format. I am assuming there is no way to convert my iTunes library from AAC to lossless, as the music data in my tracks is gone. So this would mean re-ripping my library?

Also, if I use iTunes to burn an audio CD of random music from my library, since the source data is AAC and therefore missing info, will the Audio CD also be lower quality than the commercially available audio CD of this same band?

hydrogen audio is a good source of info on compression technology. ABX testing indicates no audible difference between high bit rate mp3/aac's and lossless music.

 

[DJ in TX]

hydrogen audio is a good source of info on compression technology. ABX testing indicates no audible difference between high bit rate mp3/aac's and lossless music.

This is exactly what I wanted to hear. It would have taken forever to re-rip all my music, and likely I just wouldn't have done it. I can be pretty lazy myself

Thanks for the heads up. I'll have to check out Hydrogen audio.

 

[MDS]

If I understand correctly, MP3, AAC and AAC+ have audio bits removed for compression so that you can squeeze alot on your iPod, but the downside is that audio is then lower quality as some parts are missing. On an average system or in the car I shouldn't expect to notice a difference, but on higher end systems I might hear a difference depending on the recording. If any of this is wrong so far, just let me know.

That is correct. They are lossy compression codecs and the technique is known as 'perceptual coding'. Its model determines what you wouldn't likely be able to hear anyway (such as a soft tone masked by a louder tone) and removes that portion from the audio in order to reduce the file size.

Lower bit rates remove more of the high frequencies too (128 kbps MP3 typically removes everything from 16 kHz and up). If you use a high enough bitrate, at least 192 kbps, in the majority of cases it will be indistinguishable from the original.

For the purposes of creating a media library to save forever, it would be better to save the files in uncompressed WAV or use a lossless format to save a little space. You can then transcode those files to any compressed format you want to put them on a portable device like an iPod.

I am assuming there is no way to convert my iTunes library from AAC to lossless, as the music data in my tracks is gone. So this would mean re-ripping my library?

You can convert any format to any other format but you cannot restore what was removed during the encoding process. If you convert AAC to a lossless format, you'll have the same file in a different format. If you convert from one lossy compression format to another, the result will be worse because you'll be re-compressing a file that has already been compressed.

So, yes you must re-rip if you want the original file as it existed on a CD.

Also, if I use iTunes to burn an audio CD of random music from my library, since the source data is AAC and therefore missing info, will the Audio CD also be lower quality than the commercially available audio CD of this same band?

Same as above. When you play an AAC file (or MP3, WMA, etc) it gets converted to PCM. PCM is the format of audio on a CD and the burning application will just decode the AAC to PCM and burn it in the proper format on a CD. You'll have a CD with AAC quality tracks.

 

[Transmaniacon]

Thanks for the great info, I have been contemplating re-ripping my CDs in lossless on my PC. I use my iTouch + Apple Airport Express router to stream music from my PC to my AVR, so I might try playing the same track in different formats to see if its worthwhile.

 

[JerryLove]

For the purposes of creating a media library to save forever, it would be better to save the files in uncompressed WAV or use a lossless format to save a little space. You can then transcode those files to any compressed format you want to put them on a portable device like an iPod.

To be fair: it's more than "a little" space saved.

That said: there's a second reason I recommend lossless for archiving: the idea of "generational loss".

Us old folks certainly remember that from the analog days. The copy of a tape sounded good, but the copy of the copy of the copy was awful.

I worry about the same thing with even good lossy codecs. When you change codecs, and you eventually will, the audio file is decoded and re-encoded. You can't get your old loss back, but you can loose new things.

It's possible that the problems will never propigate into "noticeable". But given the low low cost of drive-space, and the relatively modest gains for lossy compressions, I highly recommend lossless for your archives.

For your media player? Whatever sounds good.

 

[lsiberian]

To be fair: it's more than "a little" space saved.

That said: there's a second reason I recommend lossless for archiving: the idea of "generational loss".

Us old folks certainly remember that from the analog days. The copy of a tape sounded good, but the copy of the copy of the copy was awful.

I worry about the same thing with even good lossy codecs. When you change codecs, and you eventually will, the audio file is decoded and re-encoded. You can't get your old loss back, but you can loose new things.

It's possible that the problems will never propigate into "noticeable". But given the low low cost of drive-space, and the relatively modest gains for lossy compressions, I highly recommend lossless for your archives.

For your media player? Whatever sounds good.

Well there is the opposite end when support is lost for lossless formats.