帶有AudioFileReadPackets的EXC_BAD_ACCESS

Question

我一直在嘗試按照此處的說明對本地音頻文件進行序列化，只是想將數據包直接饋送到AudioQueBuffer，而不是使用GKSession通過藍牙/ wifi將其發送。 我收到一個EXC_BAD_ACCESS錯誤：

- (void)broadcastServerMusicWithSession:(GKSession *)session playerName:(NSString *)name clients:    (NSArray *)clients
{
    self.isServer = YES;

    _session = session;
    _session.available = NO;
    _session.delegate = self;
    [_session setDataReceiveHandler:self withContext:nil];

    CFURLRef     fileURL = (__bridge CFURLRef)[[NSBundle mainBundle] URLForResource:@"mozart"                                                                       withExtension:@"mp3"]; // file URL    
    AudioFile *audioFile = [[AudioFile alloc] initWithURL:fileURL];    

    //no we start sending the data over    
    #define MAX_PACKET_COUNT    4096
    SInt64 currentPacketNumber = 0;
    UInt32 numBytes;
    UInt32 numPacketsToRead;
    AudioStreamPacketDescription    packetDescriptions[MAX_PACKET_COUNT];    

    NSInteger bufferByteSize = 4096;
    if (bufferByteSize < audioFile.maxPacketSize) bufferByteSize = audioFile.maxPacketSize; 
    numPacketsToRead = bufferByteSize/audioFile.maxPacketSize;
    UInt32 numPackets = numPacketsToRead;

    BOOL isVBR = ([audioFile audioFormatRef]->mBytesPerPacket == 0) ? YES : NO;

// this should be in a do while (numPackets < numPacketsToRead) loop.. 
// but i took it out just to narrow down the problem

    NSMutableData *myBuffer = [[NSMutableData alloc] initWithCapacity:numPackets * audioFile.maxPacketSize];

    AudioFileReadPackets (
                          audioFile.fileID,
                          NO,
                          &numBytes,
                          isVBR ? packetDescriptions : 0,
                          currentPacketNumber,
                          &numPackets,
                          &myBuffer
                          );

    NSError *error;        
    if (![session sendDataToAllPeers:packetData withDataMode:GKSendDataReliable error:&error]) 
    {
        NSLog(@"Error sending data to clients: %@", error);
    }

我知道事實上是AudioFileReadPackets調用破壞了代碼，因為如果我注釋掉它，它可以正常運行

我試過使用xcode 4.3進行Zombies分析 ，但是它只是崩潰了..我得到的一個有用的調試技巧是，當代碼崩潰時中斷並使用gdb控制台輸出錯誤代碼。.這就是我得到的：

(lldb) po [$eax className] NSException
error: warning: receiver type 'unsigned int' is not 'id' or interface pointer, consider casting it to 'id'
warning: declaration does not declare anything
error: expected ';' after expression
error: 1 errors parsing expression

但我不能做太多..任何幫助嗎？

Answer 1

原來上面的代碼有兩個問題：

1. [audioFile audioFormatRef]-> mBytesPerPacket == 0編譯器對此不滿意。如果您引用定義audioFormatRef的代碼 ，它將返回一個指向具有mBytesPerPacket字段的格式結構的指針。上面的語法不起作用

2. 我不應該提供myBuffer到AudioFileReadPackets功能（類型mistmach）..而我應該做這樣的事情：

    NSMutableData *myBuffer = [[NSMutableData alloc] initWithCapacity:numPackets * audioFile.maxPacketSize]; const void *buffer = [myBuffer bytes]; AudioFileReadPackets ( audioFile.fileID, NO, &numBytes, isVBR ? packetDescriptions : 0, currentPacketNumber, &numPackets, buffer ); 

這也有效

void *buffer = [myBuffer mutablebytes];

閱讀這篇文章以解釋這兩種選擇之間的區別