Re: [CoreAudio] General Question about Conversion
Re: [CoreAudio] General Question about Conversion
- Subject: Re: [CoreAudio] General Question about Conversion
- From: James McCartney <email@hidden>
- Date: Tue, 3 Jan 2006 11:54:48 -0800
On Jan 3, 2006, at 12:59 AM, Alexander von Below wrote:
Hello,
while I am a true believer in RTFM, I am taking the liberty to ask
in this list if reading the CoreAudio docs will yield the desired
result ;)
What we want to do is to convert as many audio formats as possible
(well, mainly mp3, aac and Apple lossless) into canonical PCM.
Another requirement is compatibility from 10.2.8 to 10.4 (Universal).
On first sight, it looks like Core Audio could fulfill all of these
requirements. However, I was unable to find any MP3, AAC or similar
codecs in the filesystem - I might have been looking for the wrong
things, though.
So, is CoreAudio what I need? Or should I look for other options?
There are several levels at which you can do this. At the lowest
level is to call the AudioConverter and AudioFile APIs. This will be
compatible back to 10.2.8 for decoding mp3, aac, and lossless
(assuming a QuickTime with which lossless was shipped has been
installed). The AudioConverter can decode any format for which codecs
are installed in the system. AudioFile does the file parsing and data
handling.
For 10.4 you have more options. You can use the ExtAudioFile API
which is a easier to use wrapper for the AudioConverter and AudioFile
APIs.
And at the highest level if you don't need direct control, your app
could spawn the command line tool "afconvert" which can do about
everything ExtAudioFile can do.
afconvert is found in /Developer/Examples/CoreAudio/Services/
AudioFileTools.
Another related question is if anyone here knows if it is possible
at all to read AAC Protected (iTMS) files. I am aware that this
would first and foremost require an agreement with Apple, but if
there is the known chance of reaching such an agreement, we would
like to try.
If there is not even a remote chance to get such permission for any
company, then there is no reason in persuing this. I am a aware of
not-quite-so-legal ways of doing this, but that is not an option.
If we can not do it with Apple's blessing, then we just won't.
The CoreAudio APIs do not provide a way to read protected files.
-- james mccartney -- apple coreaudio
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