Extract AAC from .mov

Nermal

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I have a few .rm files (RealAudio 10 AAC), and have done a "container swap" so that the AAC is now in a QuickTime container, and is therefore readable by iTunes etc. The problem is that my iPod won't read these QuickTime files. How can I extract the AAC data into an .m4a file that an iPod can play? I have QT Pro.

Thanks :)

Edit: 1000th thread in this forum :p
 

eXan

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In the File menu select export. In the list of available options select "Audio to AAC" :)

EDIT: in QuickTime of course ;)
 

eXan

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Oh sorry, my bad. :(

In QuickTime's Export window select "Sound to AIFF", then convert it to AAC in iTunes :)

P.S.: dont forget to delete aiff file :D
 

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The trouble is that converting AAC -> AIFF -> AAC is a pointless waste of quality. I'd rather keep the original AAC intact if at all possible.
 

Lacero

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You need QT Pro, but you could Command+J the open audio file, and use the Extract button to "extract" the AAC file. Then save it normally to it's own QT file.
 

Nermal

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That was my first thought, but it didn't work. It just ended up back inside a QuickTime container.
 

Lacero

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Then you'll need to do a transcode to QT's AAC format, which probably entail a quality hit.
 

Nermal

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I'll wait and see whether anyone knows a trick or two :)

I can convert to Apple Lossless in the meantime, which will allow it to play on the iPod. But 256 kb/s AAC is smaller than ~900 kb/s lossless :rolleyes:
 

wrc fan

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use the extract like mentioned above, then do a export movie to mpeg-4. then click the options button and under audio choose Pass through for the audio format. Then save. You can then rename the file to a .m4a (if you so choose) and it'll play fine.
 

Darwin

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Nermal said:
I tried that. It plays fine in QuickTime, but is full of "pops" in iTunes :confused:
This may not do anything but have you tried playing around with the equalizer in iTunes? (If you have it on then that could be the problem) If you don't have it on then I don't understand about the pops
 

Nermal

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No, I don't have the equaliser on. The pops have left me baffled! If I drag the QuickTime-generated .mp4 into iTunes, it plays fine, but won't copy to my iPod. If I rename the file to .m4a, it plays fine in QuickTime but pops in iTunes. I just tried copying the .m4a to my iPod, and it plays perfectly :confused:

I suppose that's a solution (sort of) - have two copies, an .mp4/.mov for playing in iTunes, and an .m4a for the iPod. Bit of a pain though.
 

WinterMute

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Nermal said:
The trouble is that converting AAC -> AIFF -> AAC is a pointless waste of quality. I'd rather keep the original AAC intact if at all possible.
How does this waste quality?

If you convert AAC to aiff, the quality will be the same as the original file, as aiff is essentially an uncompressed format, recoding to AAC will not effect the quality unless you drop the bit rate lower than it was originally.

I'd export to aiff from QT, throw the aiff at iTunes and re-code to AAC.

Am I missing something, sounds relatively easy to me?
 

Veldek

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WinterMute said:
If you convert AAC to aiff, the quality will be the same as the original file, as aiff is essentially an uncompressed format
I think this is true.
WinterMute said:
recoding to AAC will not effect the quality unless you drop the bit rate lower than it was originally.
But I'm not too sure about this. I thought going from AIFF to AAC always includes a quality loss, even if it was an AAC originally.
 

Nermal

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AAC is a lossy codec, so you lose quality by encoding into it. This is compounded by the fact that the original encoder (Real's) does things differently from Apple's encoder.
 

WinterMute

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Nermal said:
AAC is a lossy codec, so you lose quality by encoding into it. This is compounded by the fact that the original encoder (Real's) does things differently from Apple's encoder.
This is true, but the loss occurs in frequency terms, and those frequencies are already missing because the source is AAC. aiff preserves the quality of the source on the encode, and you lose nothing going back, because there's nothing to lose.

However, you may have a point about Real's encoder sounding different, give it a try, it might be OK.
 

WinterMute

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Veldek said:
I thought going from AIFF to AAC always includes a quality loss, even if it was an AAC originally.
Only if the source is uncompressed originally, see above post, you can't lose what isn't there in the same way that you can't replace what's missing by re-encoding to a higher bit-rate,
 

Veldek

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WinterMute said:
Only if the source is uncompressed originally, see above post, you can't lose what isn't there in the same way that you can't replace what's missing by re-encoding to a higher bit-rate,
So, going from AAC to AIFF and back to AAC gives you two identical copies of the same AAC file? I see that this could work if the algorithm used for compression doesn't compress an already compressed structure any further (what a sentence ;)).
 

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wrc fan said:
Sounds like a bug in iTunes to me. I'd submit it to Apple so they know and can hopefully fix it.
I just tried taking a regular audio CD -> AAC -> QT -> Export to MP4 -> Rename to m4a (ie. the same sort of process as these other files), and there are no pops! So it seems that Real's encoder is doing something that iTunes doesn't like.
 

WinterMute

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Veldek said:
So, going from AAC to AIFF and back to AAC gives you two identical copies of the same AAC file? I see that this could work if the algorithm used for compression doesn't compress an already compressed structure any further (what a sentence ;)).
Strictly, going from AAC to aiff has no benefit other than preserving the audio quality of the AAC file from further degradation as aiff is an uncompressed format. Recoding to AAC does recompress, but it won't change the frequency response of the original AAC.

You won't get an identical file, but the waveforms will be very similar indeed and there will be no audible change in the new AAC.

You'd need to go back and forth a few times to throw up coding errors on a grand scale, but the frequency response will stay the same.