how to free memory used by AudioFileReadPacketData - Xcode shows memory still in use

Question

I'm reading an audio file into RAM using the following method by passing an MPMediaItem object. However, each time this is called, the beginning of the function is supposed to free the memory used for the previous audio file and it doesn't, i.e., Xcode shows the memory usage keeps increasing each time the function is called and eventually the OS runs out of memory.

Am I doing anything obviously wrong?

NOTE: the below function is the only place I am using my audioData ivar

Memory allocation summary in Instruments

The same audio file cached in memory by below function

void *audioData;

- (void)playItem:(MPMediaItem *)mediaItem
{
   if (audioData != NULL) {
       NSLog(@"audio data pointer not empty");
       free (audioData);
   }

   // open audio file
   AudioFileID audioFileID;
   NSURL *mediaItemURL = [mediaItem valueForProperty:MPMediaItemPropertyAssetURL];

   OSErr err;
   err = AudioFileOpenURL((__bridge CFURLRef)mediaItemURL,
                          kAudioFileReadPermission,
                          0,
                          &audioFileID);
   NSAssert(err == noErr, @"Couldn't open audio file...");

   // read audio file properties and malloc audioData property
   UInt32 audioDataPacketCount;
   UInt32 audioDataPacketCountSize = sizeof(audioDataPacketCount);
   err = AudioFileGetProperty(audioFileID,
                              kAudioFilePropertyAudioDataPacketCount,
                              &audioDataPacketCountSize,
                              &audioDataPacketCount);
   NSAssert(err == noErr, @"Couldn't read audio file properties...");

   UInt32 audioDataByteCount;
   UInt32 audioDataByteCountSize = sizeof(audioDataByteCount);
   err = AudioFileGetProperty(audioFileID,
                              kAudioFilePropertyAudioDataByteCount,
                              &audioDataByteCountSize,
                              &audioDataByteCount);
   NSAssert(err == noErr, @"Couldn't read audio file properties...");
   audioData = malloc(audioDataByteCount);

   // read audio file packets
   err = AudioFileReadPacketData(audioFileID,
                                 false,
                                 &audioDataByteCount,
                                 NULL,
                                 0,
                                 &audioDataPacketCount,
                                 audioData);
   NSAssert(err == noErr, @"Couldn't read audio file to memory...");

}

EDIT: I used the same code structure and read the audio file data using ExtAudioFileRead function instead and memory deallocates and gets reallocated as supposedly. It may be something to do with how I'm using the AudioFileReadPacketData function =/

If you run the memory tool in instruments then you should be able to get a better idea which bit of memory is hanging about. — James Snook, Sep 27 '14 at 16:35
I see the audio files read to RAM and placed into my audioData ivar and which I can't to free... — JackyJohnson, Sep 27 '14 at 16:37
I don't understand why all those files are accumulated - they should be freed when I call free(audioData)? Why...? — JackyJohnson, Sep 27 '14 at 16:48
The "PlayFile" example of apple may help . https://developer.apple.com/library/mac/samplecode/PlayFile/Introduction/Intro.html — liaogang, Sep 28 '14 at 02:50
it's not reading the file to RAM at all - how is that supposed to help? — JackyJohnson, Sep 28 '14 at 04:30
Since you called `malloc` to alloced a block of memory , have you free them after you finish using? — liaogang, Sep 28 '14 at 06:04
That was it! I needed to make that call before freeing the pointer. If you post this answer, I'll accept it. Thank you! — JackyJohnson, Sep 28 '14 at 07:18

score 0 · Accepted Answer · edited Sep 28 '14 at 08:37

0

You need to call AudioFileClose before freeing the AudioFileID resources.

Otherwise AudioFile retains a reference to the audio data void pointer and memory cannot be freed.

if (audioData != NULL) {
   NSLog(@"audio data pointer not empty");
   AudioFileClose(audioFileID);  // <- missing call
   free (audioData);
}

edited Sep 28 '14 at 08:37

JackyJohnson

3,106
3
28
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answered Sep 28 '14 at 07:38

liaogang

508
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This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. – skuntsel Sep 28 '14 at 08:00
I don't understand what you say , @skuntsel. Sorry , English is not my mother language. Can you make it simply? – liaogang Sep 28 '14 at 08:05
You might be right with the answer, but you should expand your answer so that people reading it would be able to find it containing all the aspects of the topic. As it currently stands it is like a game for the reader. – skuntsel Sep 28 '14 at 08:10

how to free memory used by AudioFileReadPacketData - Xcode shows memory still in use

1 Answers1