Re: Getting raw audio data from an AIFF file
Re: Getting raw audio data from an AIFF file
- Subject: Re: Getting raw audio data from an AIFF file
- From: Ed Friese <email@hidden>
- Date: Wed, 12 Feb 2003 20:46:04 -0800
I was under the impression that the AudioFile stuff in the AudioToolkit
framework was the right thing to use for this kind of thing. Is that
not the case?
Ed
On Wednesday, February 12, 2003, at 04:55 PM, Brian Willoughby wrote:
Hello,
I am sorry for the delay in my response (things move fast on this
list!), but
I wanted to do a little research before replying.
I remember that the original AppKit/SoundKit "Sound" class allowed
access to
audio data, including routines for compacting the data after edits
which have
inserted or deleted samples. But a quick check of the Cocoa
documentation for
the NSSound class does not seem to reveal any access to sound data,
although
there is support for playing AIFF within a limited subset of the
possible data
formats. If you want to use Cocoa, you might be able to get at the
sound data
via -[NSSound writeToPasteboard:] or by directly accessing the _data0
and
_data1 instance variables (the former is a bit of a hack, and the
latter is a
highly contraindicated hack!). It would really be nice if Apple
implemented
all the functionality that was in the former AppKit/SoundKit Sound
class for
the newer Cocoa AppKit NSSound class. I think of the SoundKit as part
of the
AppKit, because it predates even the Foundation Kit, but technically
the
SoundKit was not part of the AppKit proper.
Fortunately, ever since NeXT let the SoundKit go to the Stanford Music
Department (I believe that was the path it took), expert programmers
have been
maintaining the original SoundKit code in the renamed SndKit, which is
distributed as part of the MusicKit. Check out MusicKit.org - a good
starting
place might be http://www.musickit.org/MusicKitConcepts/thesndkit.html
for your
particular interests.
The two options above are the most Objective-C-friendly choices I am
aware of
at this time. I would recommend the SndKit "Snd" object over hacking
too
deeply into NSSound. You should find that the SndKit is as easy to
use as
Cocoa, due to its object oriented design, as opposed to QuickTime or
other
old-school standard C libraries.
Brian Willoughby
Sound Consulting
Begin forwarded message:
From: "Andrew GFunk" <email@hidden>
To: email@hidden
Subject: Getting raw audio data from an AIFF file
Date: Sat, 08 Feb 2003 16:42:56 -0800
Hi! I'm a newbie to audio app development. Under OS X, is there an
easy way
to get at the raw audio data (PCM) of an AIFF (or similar type) file?
All I
need besides the raw audio data is the sample-rate, resolution, and
number
of channels of the sound... all the other headers that might be
included in
the file can be ditched. Is there some kind of simple service I can
use to
store the PCM portion of the file as an NSData object?
I plan on doing some DSP stuff on the raw audio data, then saving the
result
as a new file with the same sample rate, resolution and # of channels
as the
original (44.1KHz, 16-bit, stereo in most cases).
I'm writing the app in Objective-C.
Also, how would you go about spliting up the stereo data of an AIFF
file
into 2 seperate NSData objects (left and right)? Then how would you
recombine the 2 (after doing some DSP on each) to form a stereo AIFF
file
again?
Any help at all would be awesome :)
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