Saving and retrieving Sint16 from NSMutableData
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25-06-2021 - |
Question
I need somewhere to save and then to retrieve Sint16 (2 bytes).
I get:
SInt16* frames = (SInt16*)inBuffer->mAudioData;
and want to save &frames[i]
somewhere (NSMutableData?) that could later easily retrieve. I tried to save like this (in cycle):
[recordedData appendBytes:&frames[i] length:1];
and retrieve:
SInt16* framesRetrieve ;
//sets up mybytes buffer and reads in data from myData
framesRetrieve = (SInt16*)malloc([mutableData framesRetrieve]);
[mutableData getBytes:framesRetrieve];
But this return not the same as i put into.
So what could be a solution ?
thanks.
Solution
You need to know the length of the data and then you can store the whole buffer in an NSMutableData
object:
To store:
SInt16 *frames = ...;
NSUInteger length = ...; // Assuming number of elements in frames, not bytes!
NSMutableData *data = [[NSMutableData alloc] initWithCapacity:0];
[data appendBytes:(const void *)frames length:length * sizeof(SInt16)];
To retrieve:
SInt16 *frames = (SInt16 *)[data bytes];
NSUInteger length = [data length] / sizeof(SInt16);
OTHER TIPS
You are only copying one byte from a 2 byte variable. Try appending both bytes to the NSMutableData at once.
[recordedData appendBytes: frames length:sizeof(SInt16)];
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