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我想將單聲道線性pcm文件轉換爲aac文件。經過很多努力，我終於用下面的設置把它輸出，但現在文件不能播放。我真的不知道去哪裏看 - 我發現的所有例子都與我已有的類似。ExtAudioFileWrite產生不可用的m4a aac文件
我看過的所有示例都有destFormat.mBytesPerPacket = 0，但是我不能寫它然後（我得到一個-66567寫入，它解析爲kExtAudioFileError_MaxPacketSizeUnknown）。
ExtAudioFileRef sourceFile = 0;
ExtAudioFileRef destinationFile = 0;
OSStatus error = noErr;
AudioStreamBasicDescription srcFormat, destFormat;
UInt32 size = sizeof(srcFormat);
error = ExtAudioFileOpenURL((CFURLRef)self.track.location, &sourceFile);
if(error != noErr)
NSLog(@"conversion error: %i", error);
error = noErr;
ExtAudioFileGetProperty(sourceFile, kExtAudioFileProperty_FileDataFormat, &size, &srcFormat);
destFormat.mFormatID = kAudioFormatMPEG4AAC;
destFormat.mSampleRate = 22000;
destFormat.mFormatFlags = 0;
destFormat.mBytesPerPacket = 2; // must have a value or won't write apparently
destFormat.mFramesPerPacket = 0;
destFormat.mBytesPerFrame = 0;
destFormat.mChannelsPerFrame = 1;
destFormat.mBitsPerChannel = 0;
destFormat.mReserved = 0;
//create the output file
NSString *destURL = [self.track.location absoluteString];
NSLog(@"source url: %@", destURL);
destURL = [destURL substringToIndex:([destURL length] - 3)]; //remove caf extension
NSLog(@"source url with no extension: %@", destURL);
destURL = [NSString stringWithFormat:@"%@m4a",destURL]; //add acc extension
NSLog(@"dest url with correct extension: %@", destURL);
NSURL *destinationURL = [NSURL URLWithString:destURL];
size = sizeof(destFormat);
AudioFormatGetProperty(kAudioFormatProperty_FormatInfo, 0, nil, &size, &destFormat);
error = ExtAudioFileCreateWithURL((CFURLRef)destinationURL, kAudioFileM4AType, &destFormat, NULL, kAudioFileFlags_EraseFile, &destinationFile);
if(error != noErr)
NSLog(@"conversion error: %i", error);
error = noErr;
//canonical format
AudioStreamBasicDescription clientFormat;
clientFormat.mFormatID = kAudioFormatLinearPCM;
clientFormat.mSampleRate = 22000;
int sampleSize = sizeof(AudioSampleType);
clientFormat.mFormatFlags = kAudioFormatFlagsCanonical;
clientFormat.mBitsPerChannel = 8 * sampleSize;
clientFormat.mChannelsPerFrame = 1;
clientFormat.mFramesPerPacket = 1;
clientFormat.mBytesPerPacket = sampleSize;
clientFormat.mBytesPerFrame = sampleSize;
clientFormat.mFormatFlags |= kAudioFormatFlagIsNonInterleaved;
//set the intermediate format to canonical on the source file for conversion (?)
ExtAudioFileSetProperty(sourceFile, kExtAudioFileProperty_ClientDataFormat, size, &clientFormat);
//get the converter
AudioConverterRef audioConverter;
size = sizeof(audioConverter);
error = ExtAudioFileGetProperty(destinationFile, kExtAudioFileProperty_AudioConverter, &size, &audioConverter);
if(error != noErr)
NSLog(@"error getting converter: %i", error);
error = noErr;
/*UInt32 bitRate = 64000;
error = AudioConverterSetProperty(audioConverter, kAudioConverterEncodeBitRate, sizeof(bitRate), &bitRate);
if(error != noErr)
NSLog(@"error setting bit rate: %i", error);
error = noErr;*/
// set up buffers
UInt32 bufferByteSize = 32768;
char srcBuffer[bufferByteSize];
NSLog(@"converting...");
int i=0;
while (true) {
i++;
AudioBufferList fillBufList;
fillBufList.mNumberBuffers = 1;
fillBufList.mBuffers[0].mNumberChannels = 1;
fillBufList.mBuffers[0].mDataByteSize = bufferByteSize;
fillBufList.mBuffers[0].mData = srcBuffer;
// client format is always linear PCM - so here we determine how many frames of lpcm
// we can read/write given our buffer size
UInt32 numFrames = bufferByteSize/clientFormat.mBytesPerFrame;
error = ExtAudioFileRead(sourceFile, &numFrames, &fillBufList);
if(error != noErr)
NSLog(@"read error: %i run: %i", error, i);
if (!numFrames) {
// this is our termination condition
error = noErr;
break;
}
//this is the actual conversion
error = ExtAudioFileWrite(destinationFile, numFrames, &fillBufList);
if(error != noErr)
NSLog(@"conversion error: %i run: %i", error, i);
}
if (destinationFile) ExtAudioFileDispose(destinationFile);
if (sourceFile) ExtAudioFileDispose(sourceFile);
我通過放棄和使用AVAssetExportSession來解決這個問題。瘋狂的核心音頻是這樣的神祕。 – John 2010-11-04 05:11:30