Some nagging iTunes & iPod questions
in [Mac Systems]
|
From: Ian Gregory on 2 Aug 2010 13:17 On 2010-08-02, MartinC <noreply(a)nospam.invalid> wrote: > Having said that - are you sure that ALE isn't just a lossless "dialect" > from the AAC zoo? I think most devices playing back AAC are accepting > ALE-in-m4a just as well, so my guess is that it is (technically) just an > alternative compression algorithm that will not destroy data. I am no expert so I defer to Wikipedia which states: > Apple Lossless data is stored within an MP4 container with the filename > extension .m4a. It is not a variant of AAC (which is a lossy format), > but a distinct lossless format that uses linear prediction similar to > other lossless codecs such as FLAC and Shorten. http://en.wikipedia.org/wiki/Apple_Lossless Ian -- Ian Gregory http://www.zenatode.org.uk/
From: MartinC on 2 Aug 2010 13:37 Ian Gregory wrote: > I am no expert so I defer to Wikipedia which states: Thanks, so it's not a "dialect" of AAC, but rather both ALE and AAC "dialects" of .m4a so to say... Audio editors actually add their own bit to the confusion... I mainly work with AmadeusPro and that doesn't list either ALE nor AAC directly. When saving/exporting audio files, then the format is given as M4A - and then you get a selector for the compression, which is either AAC with quality settings or ALE without. Note to the original poster - "in the wild" you will find the following lossless formats: WAV (uncompressed) AIFF (uncompressed) ALE (compressed, within .m4a containers) SHN (compressed, slightly outdated these days) FLAC (compressed, widely used) APE (compressed, seems to be good with "hard to compress" sources) WV (compressed, rather rare) There used to be even more, but it will be hard to find any more decoders if you happen to locate a file...
From: Wayne C. Morris on 2 Aug 2010 13:46 In article <i36ha0$sdc$3(a)news.eternal-september.org>, Wes Groleau <Groleau+news(a)FreeShell.org> wrote: > On 08-02-2010 02:55, MartinC wrote: > > Figaro wrote: > >> (4) I am a hi-fi aficionado and import all my old CDs into apple > >> lossless files. I am told this format is virtually indistinguishable > >> from CD quality source material. > > > > To be precise... it is a bit-copy, as in "lossless". ;-) > > Is it really? Or is it as claimed, a different format alleged > to be lossless? Obviously it's not a bit-copy, since the resulting file is smaller than the original. Since it's proprietary, I doubt there's been any independent scientific analysis to determine whether it's truly lossless. If it is lossless, converting raw uncompressed digital audio to Apple Lossless and back again should give you a data stream identical to the original.
From: MartinC on 2 Aug 2010 14:10 Wayne C. Morris wrote: > Obviously it's not a bit-copy, since the resulting file is smaller than the > original. Since it's proprietary, I doubt there's been any independent > scientific analysis to determine whether it's truly lossless. I'm so used to the formats that I didn't really think (enough) before I posted... it could have been more PRECISE ;-) So - once again: The *content* of Apple Lossless (ALE) files are bit-copies, but of course not the file itself. I thought this is rather obvious. For example, ZIP and RAR are lossless formats preserving bit-copies, but of course only the *content* of the archives are bit-copies, not the archives itself. Otherwise, if the archives would be the same size as the sources, you wouldn't need them ;-) The fact that ALE is indeed lossless is not a mysterious secret - every decent audio editor will tell you, once you re-open the saved file and compare it against the original. I found that ALE compression is slightly worse compared to FLAC (once more, the *compression ratio* not the *sound* - the *sound* is identical), also FLAC is more well-known. So for long-time archives, FLAC will be best. On the other side, ALE files work better in iTunes - especially if you want to edit tags or use ReplayGain (iVolume, etc.)
From: Wayne C. Morris on 2 Aug 2010 14:18
In article <C87CA4F0.A2978%noreply(a)nospam.invalid>, MartinC <noreply(a)nospam.invalid> wrote: > Wes Groleau wrote: > > >> To be precise... it is a bit-copy, as in "lossless". ;-) > > > > Is it really? Or is it as claimed, a different format alleged > > to be lossless? > > There is so much nonsense about AAC on the net that I stopped keeping track > a long time ago... Apple Lossless is not AAC (Advanced Audio Coding). According to Wikipedia, AAC is a lossy format developed with the cooperation & input of several companies, including AT&T Bell Labs, Dolby, and Sony. It was released as an international standard in 1997. Blind tests have shown AAC gives better quality than MP3 encoded at the same bit rate. AAC support was added to iTunes 4.0 in April 2002. Apple Lossless support was added to iTunes 4.5 in April 2004. |