Objective-c - How to serialize audio file into small packets that can be played?

Question

So, I would like to get a sound file and convert it in packets, and send it to another computer. I would like that the other computer be able to play the packets as they arr

Answer 1

Here is simplest class to play files with AQ Note that you can play it from any point (just set currentPacketNumber)

#import 
#import 

@interface AudioFile : NSObject {
    AudioFileID                     fileID;     // the identifier for the audio file to play
    AudioStreamBasicDescription     format;
    UInt64                          packetsCount;           
    UInt32                          maxPacketSize;  
}

@property (readwrite)           AudioFileID                 fileID;
@property (readwrite)           UInt64                      packetsCount;
@property (readwrite)           UInt32                      maxPacketSize;

- (id) initWithURL: (CFURLRef) url;
- (AudioStreamBasicDescription *)audioFormatRef;

@end


//  AudioFile.m

#import "AudioFile.h"


@implementation AudioFile

@synthesize fileID;
@synthesize format;
@synthesize maxPacketSize;
@synthesize packetsCount;

- (id)initWithURL:(CFURLRef)url{
    if (self = [super init]){       
        AudioFileOpenURL(
                         url,
                         0x01, //fsRdPerm, read only
                         0, //no hint
                         &fileID
                         );

        UInt32 sizeOfPlaybackFormatASBDStruct = sizeof format;
        AudioFileGetProperty (
                              fileID, 
                              kAudioFilePropertyDataFormat,
                              &sizeOfPlaybackFormatASBDStruct,
                              &format
                              );

        UInt32 propertySize = sizeof (maxPacketSize);

        AudioFileGetProperty (
                              fileID, 
                              kAudioFilePropertyMaximumPacketSize,
                              &propertySize,
                              &maxPacketSize
                              );

        propertySize = sizeof(packetsCount);
        AudioFileGetProperty(fileID, kAudioFilePropertyAudioDataPacketCount, &propertySize, &packetsCount);
    }
    return self;
} 

-(AudioStreamBasicDescription *)audioFormatRef{
    return &format;
}

- (void) dealloc {
    AudioFileClose(fileID);
    [super dealloc];
}



//  AQPlayer.h

#import 
#import "AudioFile.h"

#define AUDIOBUFFERS_NUMBER     3
#define MAX_PACKET_COUNT    4096

@interface AQPlayer : NSObject {
@public
    AudioQueueRef                   queue;
    AudioQueueBufferRef             buffers[AUDIOBUFFERS_NUMBER];
    NSInteger                       bufferByteSize;
    AudioStreamPacketDescription    packetDescriptions[MAX_PACKET_COUNT];

    AudioFile * audioFile;
    SInt64  currentPacketNumber;
    UInt32  numPacketsToRead;
}

@property (nonatomic)               SInt64          currentPacketNumber;
@property (nonatomic, retain)       AudioFile       * audioFile;

-(id)initWithFile:(NSString *)file;
-(NSInteger)fillBuffer:(AudioQueueBufferRef)buffer;
-(void)play;

@end 

//  AQPlayer.m

#import "AQPlayer.h"

static void AQOutputCallback(void * inUserData, AudioQueueRef inAQ, AudioQueueBufferRef inBuffer) {
    AQPlayer * aqp = (AQPlayer *)inUserData;
    [aqp fillBuffer:(AudioQueueBufferRef)inBuffer];
}

@implementation AQPlayer

@synthesize currentPacketNumber;
@synthesize audioFile;

-(id)initWithFile:(NSString *)file{
    if ([self init]){
        audioFile = [[AudioFile alloc] initWithURL:[NSURL fileURLWithPath:file]];
        currentPacketNumber = 0;
        AudioQueueNewOutput ([audioFile audioFormatRef], AQOutputCallback, self, CFRunLoopGetCurrent (), kCFRunLoopCommonModes, 0, &queue);
        bufferByteSize = 4096;
        if (bufferByteSize < audioFile.maxPacketSize) bufferByteSize = audioFile.maxPacketSize; 
        numPacketsToRead = bufferByteSize/audioFile.maxPacketSize;
        for(int i=0; imBytesPerPacket == 0 ? YES : NO;
    AudioFileReadPackets(
                         audioFile.fileID,
                         NO,
                         &numBytes,
                         isVBR ? packetDescriptions : 0,
                         currentPacketNumber,
                         &numPackets, 
                         buffer->mAudioData
                         );

    if (numPackets > 0) {
        buffer->mAudioDataByteSize = numBytes;      
        AudioQueueEnqueueBuffer (
                                 queue,
                                 buffer,
                                 isVBR ? numPackets : 0,
                                 isVBR ? packetDescriptions : 0
                                 );


    } 
    else{
        // end of present data, check if all packets are played
        // if yes, stop play and dispose queue
        // if no, pause queue till new data arrive then start it again
    }
    return  numPackets;
}