如何将WAV/CAF文件的采样数据转换为字节数组？

Question

我需要能够以编程方式读取WAV（或CAF）文件并仅将样本（音频）数据提取为字节数组。什么是最简单/最快捷的方式来做到这一点？

Answer 1

假设你是iOS和OS X，你想AudioToolbox框架，特别是在AudioFile.h这些API（或ExtAudioFile.h如果您需要的音频数据转换为上读取另一种格式。）

例如，

#include <AudioToolbox/AudioFile.h> 

... 

AudioFileID audioFile; 
OSStatus err = AudioFileOpenURL(fileURL, kAudioFileReadPermission, 0, &audioFile); 
// get the number of audio data bytes 
UInt64 numBytes = 0; 
UInt32 dataSize = sizeof(numBytes); 
err = AudioFileGetProperty(audioFile, kAudioFilePropertyAudioDataByteCount, &dataSize, &numBytes); 

unsigned char *audioBuffer = (unsigned char *)malloc(numBytes); 

UInt32 toRead = numBytes; 
UInt64 offset = 0; 
unsigned char *pBuffer = audioBuffer; 
while(true) { 
    err = AudioFileReadBytes(audioFile, true, offset, &toRead, &pBuffer); 
    if (kAudioFileEndOfFileError == err) { 
     // cool, we're at the end of the file 
     break; 
    } else if (noErr != err) { 
     // uh-oh, some error other than eof 
     break; 
    } 
    // advance the next read offset 
    offset += toRead; 
    // advance the read buffer's pointer 
    pBuffer += toRead; 
    toRead = numBytes - offset; 
    if (0 == toRead) { 
     // got to the end of file but no eof err 
     break; 
    } 
} 

// Process audioBuffer ... 

free(audioBuffer); 

Answer 2

下面是我从Getting NSData out of music file in iPhone偷和更新的ARC

- (NSData *)readSoundFileSamples:(NSString *)filePath 
{ 

    // Get raw PCM data from the track 
    NSURL *assetURL = [NSURL fileURLWithPath:filePath]; 
    NSMutableData *data = [[NSMutableData alloc] init]; 

    const uint32_t sampleRate = 16000; // 16k sample/sec 
    const uint16_t bitDepth = 16; // 16 bit/sample/channel 
    const uint16_t channels = 2; // 2 channel/sample (stereo) 

    NSDictionary *opts = [NSDictionary dictionary]; 
    AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:assetURL options:opts]; 
    AVAssetReader *reader = [[AVAssetReader alloc] initWithAsset:asset error:NULL]; 
    NSDictionary *settings = [NSDictionary dictionaryWithObjectsAndKeys: 
           [NSNumber numberWithInt:kAudioFormatLinearPCM], AVFormatIDKey, 
           [NSNumber numberWithFloat:(float)sampleRate], AVSampleRateKey, 
           [NSNumber numberWithInt:bitDepth], AVLinearPCMBitDepthKey, 
           [NSNumber numberWithBool:NO], AVLinearPCMIsNonInterleaved, 
           [NSNumber numberWithBool:NO], AVLinearPCMIsFloatKey, 
           [NSNumber numberWithBool:NO], AVLinearPCMIsBigEndianKey, nil]; 

    AVAssetReaderTrackOutput *output = [[AVAssetReaderTrackOutput alloc] initWithTrack:[[asset tracks] objectAtIndex:0] outputSettings:settings]; 
    [reader addOutput:output]; 
    [reader startReading]; 

    // read the samples from the asset and append them subsequently 
    while ([reader status] != AVAssetReaderStatusCompleted) { 
     CMSampleBufferRef buffer = [output copyNextSampleBuffer]; 
     if (buffer == NULL) continue; 

     CMBlockBufferRef blockBuffer = CMSampleBufferGetDataBuffer(buffer); 
     size_t size = CMBlockBufferGetDataLength(blockBuffer); 
     uint8_t *outBytes = malloc(size); 
     CMBlockBufferCopyDataBytes(blockBuffer, 0, size, outBytes); 
     CMSampleBufferInvalidate(buffer); 
     CFRelease(buffer); 
     [data appendBytes:outBytes length:size]; 
     free(outBytes); 
    } 

    return data; 

}