On 6 Oct 2008, at 10:27 pm, Joseph Ayers wrote:
I got the code for extracting samples from an Audio Buffer to
compile and run without errors as:
unsigned short *ippointer = (unsigned short *)abl-
>mBuffers[0].mData;
unsigned short *idpointer = (unsigned short *)abl-
>mBuffers[1].mData;
ipbuf = [[NSMutableArray alloc] init];
idbuf = [[NSMutableArray alloc] init];
NSNumber* ipsamp = [[NSNumber alloc] init];
NSNumber* idsamp = [[NSNumber alloc] init];
The above two lines just leak two NSNumber objects, otherwise
contributing nothing useful. This isn't the problem you're having
though, so let's move on...
nsamples = abl->mBuffers[0].mDataByteSize;
for (isamp = 1; nsamples; isamp++){
What terminates this loop? Nothing that I can see - 'nsamples' isn't a
statement that does anything, since its value isn't changed within the
loop nor compared to anything.
ipsamp = [NSNumber numberWithUnsignedShort:(unsigned
short)ippointer[isamp]];
[ipbufaddObject:ipsamp];
idsamp = [NSNumber numberWithUnsignedShort:(unsigned
short)idpointer[isamp]];
[idbufaddObject:idsamp];
Are you *really* sure you want to allocate an entire object per
sample? While not directly a cause of the problem, this could place
heavy demands on your memory usage requirements. But OK, optimize
later, moving on...
NSLog(@" isamp %d ipsamp %d idsamp %d",isamp,ipsamp,idsamp);
}
2008-10-06 07:22:45.768 Roboplasm[29177:813] isamp 108534 ipsamp
4255904 idsamp 4255904
You are logging NSNumber object references using %d, which is for an
integer. Thus it's taking the address of the object and attempting to
display it as an integer. Hence the value logged is not the contents
of the number but its address.
See:
http://developer.apple.com/documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html#/
/apple_ref/doc/uid/TP40004265-SW1
You need to use %@ which will log the result of the object's -
description method, which for an NSNumber includes its contained value.
2008-10-06 07:22:45.770 Roboplasm[29177:813] isamp 108540 ipsamp
4255904 idsamp 4255904
Program received signal: “EXC_BAD_ACCESS”.
I suspect this is occurring because isamp is being incremented beyond
the last sample value in the input array, because you have no loop
termination condition.
hth,
Graham_______________________________________________
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