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Lossless AAC?

Reply #26
Should be able to do it with QuickTime Pro.  Otherwise I think it's impossible for the moment.


Lossless AAC?

Reply #28
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Should be able to do it with QuickTime Pro.

Yep.

Lossless AAC?

Reply #29
Dammit! Why can't they just support FLAC?!? Now a lot of people will have to reencode their audio collections, wasting lots of time and energy in something that's totally unnecessary.

Lossless AAC?

Reply #30
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Dammit! Why can't they just support FLAC?!? Now a lot of people will have to reencode their audio collections, wasting lots of time and energy in something that's totally unnecessary.

And now a lot of people will find their non-iTunes player suddenly cannot play certain m4a files too

Lossless AAC?

Reply #31
Unless this lossless codec is indeed an implementation of the upcoming ALS (which I find very difficult to believe considering that it's not finished IIRC), the music should not be stored in a MPEG-4 container at all.

Lossless AAC?

Reply #32
The About box in iTunes doesn't reveal the source of the lossless codec.  So it is unlikely to be FLAC.

Lossless AAC?

Reply #33
Thanks kl33per. QuickTime Pro does the decoding job. But it seems to me there's a bug. Decoded files are some frames shorter than the original WAVE file. I've tested this with EAC's 'WAV compare' tool. Can someone confirm this?

Lossless AAC?

Reply #34
Is there a way to extract the "alac" part from the m4a container?

And does it make any sense?

[span style='font-size:8pt;line-height:100%']Sorry for spreading FUD before in the thread  [/span]
Life is Real...
(But not in audio :) )

Lossless AAC?

Reply #35
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the file contains "alac", i assume this means apple lossless audio codec...

The sample description box is indeed called "ALAC", for any MPEG-4 audio codec it would definately have to be "MP4A". So if it is the new MPEG-4 ALS codec they did not add it to the file in a very compatible way. It also seems that the file doesn't have an ESDS (ESDescriptor), so finding out more is not really possible

BTW: Any MP4 reader should be able to read this file and just ignore the ALAC track as an unknown track. Crashing of a player would mean that it is buggy

Menno

Lossless AAC?

Reply #36
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Unless this lossless codec is indeed an implementation of the upcoming ALS (which I find very difficult to believe considering that it's not finished IIRC), the music should not be stored in a MPEG-4 container at all.

yeah its problematic, still it doesnt break the files

i guess apple is simply too fast, or mpeg is too slow

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Thanks kl33per. QuickTime Pro does the decoding job.

hm not here (at least the sample uploaded by kl33per)! i have qt 6.5 installed (but not itunes, which is i assume necessary)

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The sample description box is indeed called "ALAC", for any MPEG-4 audio codec it would definately have to be "MP4A". So if it is the new MPEG-4 ALS codec they did not add it to the file in a very compatible way. It also seems that the file doesn't have an ESDS (ESDescriptor), so finding out more is not really possible

still they place it under "smhd" and didnt use the "nmhd" unkown atom, so the players could detect it as audio stream i think

i doubt that it is mpeg-4 als
I know, that I know nothing (Socrates)

Lossless AAC?

Reply #37
To decode in iTunes set the import option to WAV in preferences, select the Lossless track and then select Convert to WAV in the Advanced menu.

Not tried it but it should work.

Lossless AAC?

Reply #38
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The About box in iTunes doesn't reveal the source of the lossless codec.  So it is unlikely to be FLAC.

The FLAC encoder/decoder is LGPL isn't it? That means they can modify it as much as they like and link it to anything, under any licence as long as they return any changes made to the FLAC code itself. I don't think there's an advertising clause, or is there?

edit: just checked the Safari about box which says nothing about KHTML, licenced under similar terms. edit3 : However, there is a Licence entry under the Help menu which talks about the LGPL, but that point is moot given the following info:

edit 2: just checked flac.sf.net and apparently they use Xiph's BSD licence nowadays.

Lossless AAC?

Reply #39
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The sample description box is indeed called "ALAC", for any MPEG-4 audio codec it would definately have to be "MP4A". So if it is the new MPEG-4 ALS codec they did not add it to the file in a very compatible way. It also seems that the file doesn't have an ESDS (ESDescriptor), so finding out more is not really possible

still they place it under "smhd" and didnt use an unkown atom, so the players could detect it as audio stream i think

Treating every track with a SMHD as AAC audio is wrong (ok, I guess some players might actually do that  ). So the parser will know that it is sound, but it will also know that it doesn't know what codec the track uses 

Menno

Edit: wait I meant to say YES

Lossless AAC?

Reply #40
hm they also name it "soun" in the handler reference atom (like its also the case with aac and mp3 in mp4)

what would be the more correct way to place an unspecified audio track in mp4? using "mp4a" in the sample descritption atom, but some own description (eg "alac" instead of "soun") under hdlr
or as apple does it: "soun" in hdlr and some private stuff ("alac") under "stsd"?
I know, that I know nothing (Socrates)

Lossless AAC?

Reply #41
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hm they also name it "soun" in the handler reference atom (like its also the case with aac and mp3 in mp4)

what would be the more correct way to place an unspecified audio track in mp4? using "mp4a" in the sample descritption atom, but some own description (eg "alac" instead of "soun") under hdlr
or as apple does it: "soun" in hdlr and some private stuff ("alac") under "stsd"?

All codec related stuff is in the ESDescriptor and there are fields in there where you can define your own codec. File should be exactly the same as a normal MP4 file with sound track, only ESDescriptor should have some different values to other codecs, as each codec will have different values to others codecs

Menno

Lossless AAC?

Reply #42
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To decode in iTunes set the import option to WAV in preferences, select the Lossless track and then select Convert to WAV in the Advanced menu.


This does work, but it's not a very accurate way of measuring the decoding speed because the system actually has to create the wave files which slows it down quite a bit.
But you can still use it for a comparison.

I conducted a highly scientific test using itunes, foobar and a stop watch:
itunes worked at approximately 43x to decode to wave
foobar worked at approximately 45x to decode the flac files to wave.

Running the flac files through the foobar speedmeter it decoded them at 65.60x
So I could maybe say itunes can decode at 63x on my athlon 2400+...but not really because the testing was so inaccurate.

Lossless AAC?

Reply #43
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hm they also name it "soun" in the handler reference atom (like its also the case with aac and mp3 in mp4)

what would be the more correct way to place an unspecified audio track in mp4? using "mp4a" in the sample descritption atom, but some own description (eg "alac" instead of "soun") under hdlr
or as apple does it: "soun" in hdlr and some private stuff ("alac") under "stsd"?

All codec related stuff is in the ESDescriptor and there are fields in there where you can define your own codec. File should be exactly the same as a normal MP4 file with sound track, only ESDescriptor should have some different values to other codecs, as each codec will have different values to others codecs

Menno

hm but you said that the alac files have no esdescriptor!? 

btw how can i read out the esdescriptor?
I know, that I know nothing (Socrates)

Lossless AAC?

Reply #44
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hm but you said that the alac files have no esdescriptor!? 

Yes, but since Apple uses ALAC instead of MP4A, it describes only one codec, but it's not a very nice way of doing things.

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btw how can i read out the esdescriptor?


I just debug stepped through my mp4 parser

Menno

Lossless AAC?

Reply #45
Just tried ALAC on my PowerBook...it is indeed a lot faster than FLAC (probably Altivec optimized), hitting encoding speeds of 23-24x on my G4 867 for rock music. Rush, Led Zeppelin, and Pink Floyd have compressed down to between 800-1000kbps, which falls short of what I would get with FLAC, but is much faster. Though I'm happy to now be able to easily convert my CD's to lossless for use on my Mac and iPod, I really wish Apple would have waited for MPEG-4 lossless or just implemented FLAC rather than going down the proprietary route.

Lossless AAC?

Reply #46
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Unless this lossless codec is indeed an implementation of the upcoming ALS (which I find very difficult to believe considering that it's not finished IIRC), the music should not be stored in a MPEG-4 container at all.

yeah its problematic, still it doesnt break the files

It shouldn't break the file, but seeing as it's not part of the MPEG-4 Standard, they shouldn't have used the MPEG-4 container.

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Thanks kl33per. QuickTime Pro does the decoding job.

hm not here (at least the sample uploaded by kl33per)! i have qt 6.5 installed (but not itunes, which is i assume necessary)

You need QuickTime 6.5.1.  iTunes is not nesscessary, just a registered QuickTime.

Lossless AAC?

Reply #47
Paging Josh Coalson....

    - M.

Lossless AAC?

Reply #48
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It shouldn't break the file, but seeing as it's not part of the MPEG-4 Standard, they shouldn't have used the MPEG-4 container.

hm its a private extension, which the mp4 container allows (its the same way as ahead places subtitles in mp4)
basically i think that such an extension is not good but valid if mpeg is too slow to standardize a solution on its own (eg a lossless or a subtitle format)

still mpeg is working on such solutions on its own already but it seems to be too slow to satisfy some of the markets needs already wanting the stuff now: mpeg-4 als and for subs the mpeg-4 text stream format has been finalized recently (i hope to see some mpeg-4 subtitle implementations soon)

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You need QuickTime 6.5.1.  iTunes is not nesscessary, just a registered QuickTime.

thx
I know, that I know nothing (Socrates)

Lossless AAC?

Reply #49
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Handy Concept for Concept Rock

Many music CDs contain songs that blend into each other, and importing them to iTunes may create a small gap between songs that interrupts the flow. If you use the iTunes Join Tracks feature, the program melds two or more songs into one, continuous gap-free track. So now you can enjoy listening to classical music, concept rock albums and extended dance mixes without the silent treatment.



That's odd, why didn't they just offer gapless AAC like Nero AAC does (even if it's not part of the standard).


IIRC, the problem isn't with the files but with how iTunes and the iPod plays them.  The iPod, especially, seems to introduce rather large gaps even with WAV files.

http://www.pretentiousname.com/mp3players/

 
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