Some nagging iTunes & iPod questions
in [Mac Systems]
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From: Wes Groleau on 2 Aug 2010 12:04 On 08-02-2010 10:38, MartinC 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... I never started keeping track. :-) > It *is* lossless, meaning that each and every sample keeps exactly the same > digital value that it got before. As a matter of fact, anything else would > be incredibly stupid, because Apple Lossless files are typically some 2-3% > larger than lossless FLAC files. If the two are not the same size, then at least one of them is NOT a "bit-copy" of the CD format the other poster asked about. -- Wes Groleau tprs along with some definitions and a brief history of fl teaching http://Ideas.Lang-Learn.us/barrett?itemid=1307
From: Ian Gregory on 2 Aug 2010 12:44 On 2010-08-02, MartinC <noreply(a)nospam.invalid> wrote: > There is so much nonsense about AAC on the net that I stopped keeping track > a long time ago... > > It *is* lossless, No it isn't. AAC (Advanced Audio Coding) is a lossy compression and encoding scheme for digital audio which has been standardised by ISO and IEC as part of the MPEG-2 and MPEG-4 specifications. It is the default iTunes format (songs sold through the iTunes store were AAC, protected using the FairPlay DRM system). You must be thinking of Apple Lossless, also known as Apple Lossless Encoder (ALE) or Apple Lossless Audio Codec (ALEC). This, as its name suggests, is lossless. If you want lossless compression on a Mac you are looking at ALE or FLAC. If you want smaller file sizes then you need to go to a lossy scheme such as AAC or MP3. Ian -- Ian Gregory http://www.zenatode.org.uk/
From: MartinC on 2 Aug 2010 12:59 Wes Groleau wrote: >> If the two are not the same size, then at least one of them > is NOT a "bit-copy" of the CD format the other poster asked about. Nope, because both Apple Lossless and FLAC are *compressed* formats, but the algorithms are different, and FLAC seems to be a bit better. It's like stuffing the same file into one ZIP and one RAR archive - both are lossless, but typically not the same compressed size.
From: MartinC on 2 Aug 2010 13:00 Ian Gregory wrote: > You must be thinking of Apple Lossless, also known as Apple Lossless > Encoder (ALE) or Apple Lossless Audio Codec (ALEC). This, as its name > suggests, is lossless. Sorry, slight mistake of mine, since *both* AAC and AL share the same file extension .m4a I wanted to write "...nonsense about .m4a" and switched it with AAC. It was an odd decision by Apple to use the same name, I guess a lot of the wrong information on the net actually origins from the fact that Apple Lossless files are named "something.m4a" and people then think that it must be lossy AAC. 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.
From: Ian Gregory on 2 Aug 2010 13:04
On 2010-08-02, Wes Groleau <Groleau+news(a)FreeShell.org> wrote: > If the two are not the same size, then at least one of them > is NOT a "bit-copy" of the CD format the other poster asked about. Surely a "bit-copy" of the CD format *is* CD format. What was being discussed were competing lossless audio codecs such as ALEC or FLAC. In essence, with a lossless codec you can take an audio file, compress it to produce a smaller file, then decompress that and recover exactly the original file. With a lossy codec you generally get a smaller compressed file but can never recover the original file, only something that sounds nearly the same. So given that all lossless codecs can recover exactly the original file what is to choose between them? Compression ratio and processing power required to compress and decompress. You could use a general purpose compression algorithm such as gzip to compress audio files but one designed specifically for audio should generally give higher compression ratios (though not of course as high as lossy audio codecs). Ian -- Ian Gregory http://www.zenatode.org.uk/ |