Re: [NEWBIE] Old thread and Vu-Meters
Re: [NEWBIE] Old thread and Vu-Meters
- Subject: Re: [NEWBIE] Old thread and Vu-Meters
- From: kelly jacklin <email@hidden>
- Date: Tue, 9 Aug 2005 06:04:22 -0700
On Aug 9, 2005, at 3:54 AM, Sanri Parov wrote:
I'm new to this list and I was making my way to get a functional
Vu-meter using a NSProgressBar in my Cocoa application, when I went
stuck with CoreAudio.
CoreAudio is powerful but very complex.
In particular I have problems in comprehending the answer Kelly
Jacklin
gave to Michael Hanna in the thread :
http://lists.apple.com/archives/coreaudio-api/2005/Feb/msg00021.html
In the same way as Michael Hanna I'm getting a lot of zeroes from the
NSLog and I can't figure why.
What is the way to use correctly SOUND_PRINTOUT_SIZE ?
Could you give me an hand?
I am not familiar with whatever code you are getting
SOUND_PRINTOUT_SIZE from, but my reply to the original poster was
using a count (SOUND_PRINTOUT_SIZE) as a _byte_ count for copying
samples from a buffer, but then assuming that the resulting copied
data would contain that same number of _samples_. Since samples are
typically floats (depending on where your code lives), this resulted
in (for the original poster) 1/4 the samples getting copies into the
copy buffer, which is why he saw the first few sample values being
correct, and subsequent ones being wrong (uninitialized or zero or
whatever, depending on the previous contents of the buffer).
I have no idea what the problems you are encountering would be, but
just be careful of assumptions that a sample count is the same as a
memory size (as was the case for the original poster), as it only is
for very unusual (nowadays) audio streams (namely 8-bit integer
uncompressed)...
On a side note, I will be very surprised indeed if an NSProgressBar
provides sufficiently responsive performance to implement a VU
meter... You might take a gander at the MeterView class in the
CarbonGenericView for tips on drawing meters that are reasonably
responsive, although the end result is not exactly the most pleasing
visual content in the world.
Hope this helps, and if not, please provide more specifics (like
actual code snippets) to help direct further responses.
kelly
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