ioscmallocextaudiofile

Massive memory spike when reading audio file

I am currently reading audio floats from a file using Dirac's (OSStatus) readFloatsConsecutive:(SInt64)numFrames intoArray:(float**)audio function. I create a pointer of float **

arrayToFill = malloc(channelCount * sizeof(float*));

for(int i = 0; i < channelCount; ++i)
{
    arrayToFill[i] = malloc(frameCount * sizeof(float));
}

and pass it to the Dirac function I get a massive memory spike when all the floats are malloced.

In instruments I get spikes that increase about 90MB, and for some reason this app still runs on the device.

would e.g. 15839544 * 2 number of floats cause these massive spikes?

How can it use so much memory? Is it virtual memory? I dont see any VM allocations.

I dont see how loading a single file of e.g. 5MB audio file can result in such massive spikes in memory.

Solution

  • would e.g. 15839544 * 2 number of floats cause these massive spikes?

    Yes, absolutely. A float is 4 bytes, so two arrays of 15.8 million floats apiece is around 120 MB total.

    As far as how you're ending up with this from a 5 MB input file: Audio compression is an amazing thing. :)