Apple Lossless conversion

Posted:
in iPod + iTunes + AppleTV edited January 2014
I noticed the other day that there is now an option within the context menu in iTunes to "Create Apple Lossless Version". I was wondering if this actually created a higher sound quality track or just expanded the file to lossless size with the same quality. I would think that you wouldn't be able to upscale music already encoded in .mp3 or AAC because there is lost data. Then I thought that because it's a predictable algorithm to encode in any format, why couldn't the lost data be predicted and replaced? Also, why even have that option if it's not really going to do anything but expand files without providing a high sound quality?

Comments

  • Reply 1 of 15
    No, once it is lossy it is lossy forever. Predicting the lost data is exactly what the decoding/playback software does. It makes no sense to do that first, and store that predicted data on your valuable hard drive space when the output is going to be the same.



    The option is there because there is always an option to "Create YYYYY Version" when your settings for ripping are set to "YYYYY". For instance, I rip to AAC, so in my menu, it will always say "Create AAC Version". Your iTunes is set to rip at lossless, so it shows the lossless option, even though you will not be improving sound quality of the files you already have.



    Quote:
    Originally Posted by maimezvous View Post


    I noticed the other day that there is now an option within the context menu in iTunes to "Create Apple Lossless Version". I was wondering if this actually created a higher sound quality track or just expanded the file to lossless size with the same quality. I would think that you wouldn't be able to upscale music already encoded in .mp3 or AAC because there is lost data. Then I thought that because it's a predictable algorithm to encode in any format, why couldn't the lost data be predicted and replaced? Also, why even have that option if it's not really going to do anything but expand files without providing a high sound quality?



  • Reply 2 of 15
    Thank you.



    Quote:
    Originally Posted by tonton View Post


    No, once it is lossy it is lossy forever. Predicting the lost data is exactly what the decoding/playback software does. It makes no sense to do that first, and store that predicted data on your valuable hard drive space when the output is going to be the same.



    The option is there because there is always an option to "Create YYYYY Version" when your settings for ripping are set to "YYYYY". For instance, I rip to AAC, so in my menu, it will always say "Create AAC Version". Your iTunes is set to rip at lossless, so it shows the lossless option, even though you will not be improving sound quality of the files you already have.



  • Reply 3 of 15
    mr. hmr. h Posts: 4,740member
    Quote:
    Originally Posted by tonton View Post


    No, once it is lossy it is lossy forever.



    Yes.





    Quote:
    Originally Posted by tonton View Post


    Predicting the lost data is exactly what the decoding/playback software does.



    No.



    Compression works by looking at the frequency spectrum of the music. Frequency components that are theoretically masked by other components are removed, reducing the amount of information in the music, enabling it to be encoded at a smaller bit rate. Advanced models of human hearing and perception are used to predict which frequencies are "inaudible". However, the lower the target bitrate, the more information needs to be removed and eventually listeners can tell the quality is lower than the original source.



    All decoding does is change the mp3/aac representation (which is still in the frequency domain) of the music into linear PCM, which is the kind of time-domain representation a DAC needs; there is some filtering, but no guessing as to what information may have been removed in the encoding process.



    The reason you can't work out what information has been removed despite the removal algorithm being known, is that information removal is a "many-to-one" operation. For a given 128 kbps AAC track, there's an infinite (or at least, very very large) number of uncompressed files that it could have come from.
  • Reply 4 of 15
    benroethigbenroethig Posts: 2,782member
    Well, not exactly. You could burn it to CD and re-import it as different format.
  • Reply 5 of 15
    mr. hmr. h Posts: 4,740member
    Quote:
    Originally Posted by BenRoethig View Post


    Well, not exactly. You could burn it to CD and re-import it as different format.



    What is this a response to?
  • Reply 6 of 15
    Quote:
    Originally Posted by Mr. H View Post


    What is this a response to?



    He is talking about taking a lossy compression, gimping it further by burning it to a Audio CD and then importing it back as lossless.
  • Reply 7 of 15
    Quote:
    Originally Posted by tonton View Post


    No, once it is lossy it is lossy forever. Predicting the lost data is exactly what the decoding/playback software does. It makes no sense to do that first, and store that predicted data on your valuable hard drive space when the output is going to be the same.



    The option is there because there is always an option to "Create YYYYY Version" when your settings for ripping are set to "YYYYY". For instance, I rip to AAC, so in my menu, it will always say "Create AAC Version". Your iTunes is set to rip at lossless, so it shows the lossless option, even though you will not be improving sound quality of the files you already have.



    When I converted a download to ALAC I was monitoring download activity on the network. During the conversion data was coming in which I assumed was the lost data from the compressed files. It ceased exactly when the conversion finished. Is this not true. If not I agree what is the point at all?
  • Reply 8 of 15
    Quote:
    Originally Posted by uksteve View Post


    When I converted a download to ALAC I was monitoring download activity on the network. During the conversion data was coming in which I assumed was the lost data from the compressed files. It ceased exactly when the conversion finished. Is this not true. If not I agree what is the point at all?



    ? And from where would it be pulling that data? There's no magical repository of lossless files somewhere on the Internet from which any application can freely pull what it needs. You can't make lossy lossless. You can't just plug in data where it 'needs to be' to make a compressed file into an ALAC or what have you.
  • Reply 9 of 15
    Quote:
    Originally Posted by Tallest Skil View Post


    ? And from where would it be pulling that data? There's no magical repository of lossless files somewhere on the Internet from which any application can freely pull what it needs. You can't make lossy lossless. You can't just plug in data where it 'needs to be' to make a compressed file into an ALAC or what have you.



    Well, I was assuming if apple made this feature available it would be coming from itunes. Again, if it doesn't then why would anyone ever want to take up more room with the same information and why would Apple spend the time making this a feature???
  • Reply 10 of 15
    Quote:
    Originally Posted by uksteve View Post


    Well, I was assuming if apple made this feature available it would be coming from iTunes.



    I'm saying the "feature" can't possibly and therefore does not exist.



    Quote:

    Again, if it doesn't…



    If what doesn't?



    Quote:

    …then why would anyone ever want to take up more room with the same information…



    Lossy and Lossless are NOT the same information. Apple knows that anyone who's reencoding their stuff is intelligent enough to know what the concept of reencoding entails or at least has a basic understanding of how the concept of the laws of thermodynamics translate to data insofar as you can't create something from nothing.



    You're saying that if it's not actually giving you the "lost" information for free that Apple shouldn't offer the option? That's silly.
  • Reply 11 of 15
    mr. hmr. h Posts: 4,740member
    Quote:
    Originally Posted by uksteve View Post


    Again, if it doesn't then why would anyone ever want to take up more room with the same information and why would Apple spend the time making this a feature???



    You've read this thread from the start, right? (It's not exactly long!). Are you saying that if you've got your import settings set to lossless, and you then go and select a file in your library that is lossy encoded, that Apple should grey out the "Create?" menu item just to avoid confusing people who don't understand?
  • Reply 12 of 15
    Quote:
    Originally Posted by Mr. H View Post


    You've read this thread from the start, right? (It's not exactly long!). Are you saying that if you've got your import settings set to lossless, and you then go and select a file in your library that is lossy encoded, that Apple should grey out the "Create?" menu item just to avoid confusing people who don't understand?



    This was my first download from itunes because I heard you could now download lossless which it wasn't and I was given no option on download format before it started. I found the option to convert immediately after and was hopeful that would be feasible for something I bought from itunes. I'm sure your right that it isn't so...........

    BUT, the question is valid, why would anyone ever want to do that if it remained compressed? What scenario might that be a good idea? My logic is sound in that people don't spend time making something available that has no purpose at all.

    Can you give a scenario that might change my mind? Does nayone know the answer to this or are you all just guessing?........Anyone from itunes on here that can speak to this?
  • Reply 13 of 15
    mr. hmr. h Posts: 4,740member
    Quote:
    Originally Posted by uksteve View Post


    BUT, the question is valid, why would anyone ever want to do that if it remained compressed? What scenario might that be a good idea? My logic is sound in that people don't spend time making something available that has no purpose at all.

    Can you give a scenario that might change my mind? Does nayone know the answer to this or are you all just guessing?........Anyone from itunes on here that can speak to this?



    The point is that that menu item always reads "Create xxx Version", where "xxx" is whatever compressor you have selected in your import preferences. e.g. If your import preference is set to AAC, the menu item will read "Create AAC Version". I grant you that if your import setting is "lossless", it's difficult to think of a situation where you'd want to take a lossy compressed file and turn it into a lossless file, but does that really mean Apple should disable the option whenever a compressed file is selected? That would be pretty annoying to anyone who actually wanted to do it for whatever reason.



    Anyway, I don't blame you for thinking that maybe the "Create Lossless Version" would give you what you were originally expecting; I can see your logic. Perhaps a little explanation message with a "dont' show this again" tickbox would be helpful if anyone were to choose the "Create Lossless Version" on a lossy compressed track.
  • Reply 14 of 15
    Quote:
    Originally Posted by Mr. H View Post


    The point is that that menu item always reads "Create xxx Version", where "xxx" is whatever compressor you have selected in your import preferences. e.g. If your import preference is set to AAC, the menu item will read "Create AAC Version". I grant you that if your import setting is "lossless", it's difficult to think of a situation where you'd want to take a lossy compressed file and turn it into a lossless file, but does that really mean Apple should disable the option whenever a compressed file is selected? That would be pretty annoying to anyone who actually wanted to do it for whatever reason.



    Anyway, I don't blame you for thinking that maybe the "Create Lossless Version" would give you what you were originally expecting; I can see your logic. Perhaps a little explanation message with a "dont' show this again" tickbox would be helpful if anyone were to choose the "Create Lossless Version" on a lossy compressed track.



    I see. That makes sense now.

    Does that mean I'm back to buying CD's from Amazon and ripping them? Was that misinformation that itunes now offers lossless for download?

    Thanks.
  • Reply 15 of 15
    mr. hmr. h Posts: 4,740member
    Quote:
    Originally Posted by uksteve View Post


    Was that misinformation that itunes now offers lossless for download?

    Thanks.



    Yes, that was misinformation. iTunes only sells in 256 kbps AAC.



    There are other stores that sell lossless files, but these tend not to be from "mainstream" artists (e.g. Linn Records). They also mostly sell in FLAC rather than Apple Lossless (aka ALAC), but if you need ALAC for iTunes compatibility, as the compression is lossless you can safely convert to any other lossless format without loss of quality. XLD is an excellent freeware tool for OS X that can do such conversions.
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