AudioQueueキューに入れられたデータの再生長を調べる方法

Question

私はAudioQueueを使っていくつかの曲をストリーミングしています。私の質問は、すでにキューに入れられているバッファの再生の長さをどうやって教えてくれるのですか？私は一度に2秒間のデータをストリーミングしたいのですが、問題は、実際に2秒分の音楽にどれくらいのバイトが対応しているかを知ることです（私はいつも2秒先になります）。

おかげ

ダニエル

Answer 1

ここでは、オーディオファイルサービスを使用して、ビットレート/パケット/フレームデータを取得して、x秒に対応する音楽ファイルのバイト数を取得するクラスです。例はmp3およびm4aファイルでテストされています

ヘッダー

#import <Foundation/Foundation.h> 
#import <AudioToolbox/AudioToolbox.h> 
@interface MusicChunker : NSObject 
{ 
    AudioFileID audioFile; 
    int _sampleRate; 
    int _totalFrames; 
    UInt64 _framesPerPacket; 
    UInt64 _totalPackets; 
    UInt64 fileDataSize; 
    AudioFilePacketTableInfo _packetInfo; 
    int _fileLength; 
    AudioStreamBasicDescription _fileDataFormat; 
    NSFileHandle * _fileHandle; 
    int _packetOffset; 
    int _totalReadBytes; 
    int _maxPacketSize; 
    BOOL firstTime; 
    BOOL _ism4a; 
} 
-(id)initWithURL:(NSURL*)url andFileType:(NSString*)ext; 
//gets next chunk that corresponds to seconds of audio 
-(NSData*)getNextDataChunk:(int)seconds; 
@end 

実装

#import "MusicChunker.h" 
void ReportAudioError(OSStatus statusCode); 
@implementation MusicChunker 

- (id)init 
{ 
    self = [super init]; 
    if (self) { 
     // Initialization code here. 
    } 

    return self; 
} 
void ReportAudioError(OSStatus statusCode) { 
    switch (statusCode) { 
     case noErr: 
      break; 
     case kAudioFileUnspecifiedError: 
      [NSException raise:@"AudioFileUnspecifiedError" format:@"An unspecified error occured."]; 
      break; 
     case kAudioFileUnsupportedDataFormatError: 
      [NSException raise:@"AudioFileUnsupportedDataFormatError" format:@"The data format is not supported by the output file type."]; 
      break; 
     case kAudioFileUnsupportedFileTypeError: 
      [NSException raise:@"AudioFileUnsupportedFileTypeError" format:@"The file type is not supported."]; 
      break; 
     case kAudioFileUnsupportedPropertyError: 
      [NSException raise:@"AudioFileUnsupportedPropertyError" format:@"A file property is not supported."]; 
      break; 
     case kAudioFilePermissionsError: 
      [NSException raise:@"AudioFilePermissionsError" format:@"The operation violated the file permissions. For example, an attempt was made to write to a file opened with the kAudioFileReadPermission constant."]; 
      break; 
     case kAudioFileNotOptimizedError: 
      [NSException raise:@"AudioFileNotOptimizedError" format:@"The chunks following the audio data chunk are preventing the extension of the audio data chunk. To write more data, you must optimize the file."]; 
      break; 
     case kAudioFileInvalidChunkError: 
      [NSException raise:@"AudioFileInvalidChunkError" format:@"Either the chunk does not exist in the file or it is not supported by the file."]; 
      break; 
     case kAudioFileDoesNotAllow64BitDataSizeError: 
      [NSException raise:@"AudioFileDoesNotAllow64BitDataSizeError" format:@"The file offset was too large for the file type. The AIFF and WAVE file format types have 32-bit file size limits."]; 
      break; 
     case kAudioFileInvalidPacketOffsetError: 
      [NSException raise:@"AudioFileInvalidPacketOffsetError" format:@"A packet offset was past the end of the file, or not at the end of the file when a VBR format was written, or a corrupt packet size was read when the packet table was built."]; 
      break; 
     case kAudioFileInvalidFileError: 
      [NSException raise:@"AudioFileInvalidFileError" format:@"The file is malformed, or otherwise not a valid instance of an audio file of its type."]; 
      break; 
     case kAudioFileOperationNotSupportedError: 
      [NSException raise:@"AudioFileOperationNotSupportedError" format:@"The operation cannot be performed. For example, setting the kAudioFilePropertyAudioDataByteCount constant to increase the size of the audio data in a file is not a supported operation. Write the data instead."]; 
      break; 
     case -50: 
      [NSException raise:@"AudioFileBadParameter" format:@"An invalid parameter was passed, possibly the current packet and/or the inNumberOfPackets."]; 
      break; 
     default: 
      [NSException raise:@"AudioFileUknownError" format:@"An unknown error type %@ occured. [%s]", [NSNumber numberWithInteger:statusCode], (char*)&statusCode]; 
      break; 
    } 
} 

+ (AudioFileTypeID)hintForFileExtension:(NSString *)fileExtension 
{ 
    AudioFileTypeID fileTypeHint = kAudioFileAAC_ADTSType; 
    if ([fileExtension isEqual:@"mp3"]) 
    { 
     fileTypeHint = kAudioFileMP3Type; 
    } 
    else if ([fileExtension isEqual:@"wav"]) 
    { 
     fileTypeHint = kAudioFileWAVEType; 
    } 
    else if ([fileExtension isEqual:@"aifc"]) 
    { 
     fileTypeHint = kAudioFileAIFCType; 
    } 
    else if ([fileExtension isEqual:@"aiff"]) 
    { 
     fileTypeHint = kAudioFileAIFFType; 
    } 
    else if ([fileExtension isEqual:@"m4a"]) 
    { 
     fileTypeHint = kAudioFileM4AType; 
    } 
    else if ([fileExtension isEqual:@"mp4"]) 
    { 
     fileTypeHint = kAudioFileMPEG4Type; 
    } 
    else if ([fileExtension isEqual:@"caf"]) 
    { 
     fileTypeHint = kAudioFileCAFType; 
    } 
    else if ([fileExtension isEqual:@"aac"]) 
    { 
     fileTypeHint = kAudioFileAAC_ADTSType; 
    } 
    return fileTypeHint; 
} 

-(id)initWithURL:(NSURL*)url andFileType:(NSString*)ext 
{ 
    self = [super init]; 
    if (self) { 
     // Initialization code here. 
     //OSStatus theErr = noErr; 
     if([ext isEqualToString:@"mp3"]) 
     { 
      _ism4a=FALSE; 
     } 
     else 
      _ism4a=TRUE; 
     firstTime=TRUE; 
     _packetOffset=0; 
     AudioFileTypeID hint=[MusicChunker hintForFileExtension:ext]; 
     OSStatus theErr = AudioFileOpenURL((CFURLRef)url, kAudioFileReadPermission, hint, &audioFile); 
     if(theErr) 
     { 
      ReportAudioError(theErr); 

     } 

     UInt32 thePropertySize;// = sizeof(theFileFormat); 

     thePropertySize = sizeof(fileDataSize); 
     theErr = AudioFileGetProperty(audioFile, kAudioFilePropertyAudioDataByteCount, &thePropertySize, &fileDataSize); 
     if(theErr) 
     { 
      ReportAudioError(theErr); 

     } 

     theErr = AudioFileGetProperty(audioFile, kAudioFilePropertyAudioDataPacketCount, &thePropertySize, &_totalPackets); 
     if(theErr) 
     { 
      ReportAudioError(theErr); 

     } 
     /* 
     UInt32 size; 

     size= sizeof(_packetInfo); 
     theErr= AudioFileGetProperty(audioFile, kAudioFilePropertyPacketTableInfo, &size, &_packetInfo); 
    g(@"Key %@", key); 
     } 

     if(theErr) 
     { 
      ReportAudioError(theErr); 
     } 
     */ 
     UInt32 size; 
     size=sizeof(_maxPacketSize); 
     theErr=AudioFileGetProperty(audioFile, kAudioFilePropertyMaximumPacketSize , &size, &_maxPacketSize); 

     size = sizeof(_fileDataFormat); 
     theErr=AudioFileGetProperty(audioFile, kAudioFilePropertyDataFormat, &size, &_fileDataFormat); 
     _framesPerPacket=_fileDataFormat.mFramesPerPacket; 
     _totalFrames=_fileDataFormat.mFramesPerPacket*_totalPackets; 

     _fileHandle=[[NSFileHandle fileHandleForReadingFromURL:url error:nil] retain];  
     _fileLength=[_fileHandle seekToEndOfFile]; 
     _sampleRate=_fileDataFormat.mSampleRate; 
     _totalReadBytes=0; 
     /* 
     AudioFramePacketTranslation tran;//= .mFrame = 0, .mPacket = packetCount - 1, .mFrameOffsetInPacket = 0 }; 
     tran.mFrame=0; 
     tran.mFrameOffsetInPacket=0; 
     tran.mPacket=1; 
     UInt32 size=sizeof(tran); 
     theErr=AudioFileGetProperty(audioFile, kAudioFilePropertyPacketToFrame, &size, &tran); 
     */ 
     /* 
     AudioBytePacketTranslation bt; 
     bt.mPacket=4; 
     bt.mByteOffsetInPacket=0; 
     size=sizeof(bt); 
     theErr=AudioFileGetProperty(audioFile, kAudioFilePropertyPacketToByte, &size, &bt); 
     */ 


    } 

    return self; 
} 
//gets next chunk that corresponds to seconds of audio 
-(NSData*)getNextDataChunk:(int)seconds 
{ 

    //NSLog(@"%d, total packets",_totalPackets); 

    if(_packetOffset>=_totalPackets) 
     return nil; 

    //sampleRate * seconds = number of wanted frames 
    int framesWanted= _sampleRate*seconds; 
    NSData *header=nil; 
    int wantedPackets= framesWanted/_framesPerPacket; 
    if(firstTime && _ism4a) 
    { 
     firstTime=false; 
     //when we have a header that was stripped off, we grab it from the original file 
     int totallen= [_fileHandle seekToEndOfFile]; 
     int dif=totallen-fileDataSize; 
     [_fileHandle seekToFileOffset:0]; 
     header= [_fileHandle readDataOfLength:dif]; 
    } 



    int packetOffset=_packetOffset+wantedPackets; 

    //bound condition 
    if(packetOffset>_totalPackets) 
    { 
     packetOffset=_totalPackets; 
    } 


    UInt32 outBytes; 

    UInt32 packetCount = wantedPackets; 
    int x=packetCount * _maxPacketSize; 
    void *data = (void *)malloc(x); 

    OSStatus theErr=AudioFileReadPackets(audioFile, false, &outBytes, NULL, _packetOffset, &packetCount, data); 

    if(theErr) 
    { 
     ReportAudioError(theErr); 
    } 
    //calculate bytes to read 

    int bytesRead=outBytes; 

    //update read bytes 
    _totalReadBytes+=bytesRead; 
    // NSLog(@"total bytes read %d", _totalReadBytes); 
    _packetOffset=packetOffset; 



    NSData *subdata=[[NSData dataWithBytes:data length:outBytes] retain];  

    free(data); 

    if(header) 
    { 
     NSMutableData *data=[[NSMutableData alloc]init]; 
     [data appendData:header]; 
     [data appendData:subdata]; 
     [subdata release]; 
     return [data autorelease]; 
    } 

    return [subdata autorelease]; 
} 

@end 

Answer 2

曲は、任意の圧縮フォーマットであり、そしてあなたは正確に2秒切れ端をしたい場合は、まず生のPCMサンプルまたはWAVデータに曲を変換する必要があります（AVAssetReader、ら等）。次に、既知のサンプルレートでサンプルを数えることができます。例えば44.1kサンプルレートの88200フレームは2秒分の価値があります。