Re: A couple of high-level questions
Re: A couple of high-level questions
- Subject: Re: A couple of high-level questions
- From: William Stewart <email@hidden>
- Date: Wed, 4 Feb 2004 16:52:02 -0800
We're about to rev the CoreAudio SDK (yes, I know I keep saying this,
but really we are going to soon!)
That has some splendid examples to take files, convert them into PCM
(regardless of their original format), including an example we've just
finished adding that will also read data from a QT movie and let you
play it through Core Audio directly. I think that would be a good basis
for the kind of thing you are proposing
Bill
On 03/02/2004, at 9:05 PM, Jens Bauer wrote:
Hi Hamish,
I can't answer the audio-questions, I'll leave those up to the
experts. :)
But when it comes to displaying information in real-time, I have some
(minor) experience.
When I wrote an oscilloscope, I found out that...
* Using NSBezierPath is a very stupid idea. =)
* Using NSRectFill is performing a bit better, but not excellent.
* QuickDraw seems to work faster.
* Drawing directly into an NSImage and blitting that onto the screen
seems to work for small oscilloscopes.
* Using OpenGL and drawing lines using quads seems to be excellent.
(if anyone disagrees, please override my email)
On Wednesday, Feb 4, 2004, at 05:06 Europe/Copenhagen, Hamish Allan
wrote:
I'm planning to write an application with an interface allowing for
direct interaction with a visual representation of an audio file
(c.f., Sound Studio or Soundtrack Loop Utility).
I want to be able to read a variety of file formats (AIFF, WAV, MP3,
AAC), but get access to PCM data for direct manipulation, Fourier
analysis, etc. I am assuming that this can be achieved through
QuickTime?
Then I want to be able to correlate the visual representation with
the audio during playback (e.g., the canonical line which moves
across the screen showing which part of the sample is currently
playing). I'm thinking I would do this by invalidating a custom
NSView during those callbacks in which I calculate that the line
needs moved. Is this a reasonable way to do it?
Is CoreAudio better suited to this purpose than the Carbon Sound
Manager? Also, I am wondering what I might gain (apart from minimal
performance increments) by using CoreAudio instead of PortAudio?
Love,
Jens
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