Extract AAC from .mov

[Veldek]

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.

But now, don't you contradict yourself? Even a degradation which is so small that you can't hear it, is still a degradation. So there is a quality loss, because I don't think that you can say that a quality loss only occurs when the owner does notice it (or does care about it).

I have to admit though, that I don't know what frequency response means...

 

[wrc fan]

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.

I thought that might be the case. I was trying to figure out how to let them know, but the iTunes feedback page seems to be solely about the music store.

 

[wrc fan]

I have to admit though, that I don't know what frequency response means...

Frequency response is what frequencies in a waveform are playable by a certain system... and I think in the strict definition of it, it really has nothing to do with a digital audio file, but a playback device (such as speakers), an amplifier, a microphone, etc. What WinterMute probably means is just that the audio is already at 44.1kHz and so changing it to another format shouldn't change the waveform too much if you keep that same freqency (I am not saying whether that statement is correct or incorrect cause it's really only you that can decide if you notice changes)

 

[eXan]

AAC is a lossy codec, so you lose quality by encoding into it.

If you do what I told you to do, the quality difference should not be very big, at least try to notice it!

 

[Eniregnat]

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.

RAW, WAV and AIFF are all virtualy the same and can (most often is) are lossless. Audiofiles will always say that digital is lossless, but there are times to use pi and times to use an aproximation of pi. Anti-aliasing wont be an issue either.

The major diffrences between the three are the primarly platforms (RAW- universal, often SUN and once Apple, WAV-PCs, and AIFF - Apple). RAW has not headers- no envelope and its endianness is not noted, nor is any other information about the recording, it is just RAW audio informaition, kind of like looking at a GIF with out knowing what palet is used. WAV and AIFF are virtualy the same with the endianness being diffrent and the headers being diffrent. If you loose any information between itentical ACC formats with an interpolated highquality encodeing format inbetween, I really doubt that you will notice the diffrence. Though if you do, you might look into using a routing program to an encoder, like soundflower or audiohjack to logicPro or QTP.

Sorry, I just went through a bit at work where I had to explain the diffrence between dozens of formats and their pros and cons. The rant is really just venting.

You actualy brought up a good point. There is a need for an automatic stand alone lossless audio extractor. Hummm. Perhaps when I learn to code.

 

[Nermal]

Sounds like a bug in iTunes to me. I'd submit it to Apple so they know and can hopefully fix it.

In case anyone cares, this problem still exists in iTunes 5.

 

[Nermal]

In case anyone's still reading this, iTunes 6 now skips the "poppy" files entirely and won't play them at all.

 

[wrc fan]

In case anyone's still reading this, iTunes 6 now skips the "poppy" files entirely and won't play them at all.

Is that an improvement? Heh. It's too bad that Apple's not fixing whatever the problem is with playing them.

 

[dejo]

FYI:

Multi-compression theory tested: Loss is real!

 

[jowie]

I know this is a very old post, but I just thought I'd update it, since I Googled and followed the processes here due to having the same issue as Nermal.

I managed to do the AAC export via MP4 (passthru), renamed to .m4a and imported into iTunes 8.1... Worked fine for me so thanks

 

[porg]

I grabbed the MP4 variant of a YouTube music video in Firefox via the plugin DownloadHelper.

1. I opened the .mp4 file in QuickTime.
2. I opened the movie property window via cmd-J.
3. The movie had both an audio and video track, I extracted the audio track.
4. A new untitled movie window opens. I exported this file via the settings Movie > MP4 and Options > Audio > Format > Pass-through and used "m4a" as the file suffix.

With the resulting files, I had the following results:

• QuickTime Player 7.6.2 (518): Played perfectly without any pops, and to my ears it was incomparable to the original mp4 file!
• iTunes 8.2 (23): Same as in QT Player!.

Note: If you only extract the audio track, then save as a QuickTime movie, and later export the audio track as MP4 via the audio pass-through, the file plays well in QT Player, but in iTunes it shows as a file with some weird track length, 760 hours instead of the correct 5 minutes, and playback fails.