使用音頻單元錄制音頻，每個文件以X秒數分割

Question

我已經來這幾天了。 我對框架的音頻單元層不是很熟悉。 有人可以給我指出一個完整的示例，該示例說明如何讓用戶以x個間隔即時記錄和寫入文件。 例如，用戶按下記錄，我想每10秒寫入一個文件，在第11秒，它將寫入下一個文件，而在第21秒，這是同一件事。 因此，當我錄制25秒的音頻字時，它將產生3個不同的文件。

我已經使用AVCapture嘗試過此操作，但它會在中間產生點擊和彈出聲。 我已經閱讀了它，這是由於讀寫操作之間的毫秒數所致。 我已經嘗試過Audio Queue Services，但是知道我正在使用的應用程序之后，我需要對音頻層進行完全控制。 所以我決定選擇Audio Unit。

Answer 1

我想我越來越近了……仍然迷路了。 我最終使用了超凡音頻引擎（TAAE）。 我現在正在看AEAudioReceiver，我的回調代碼如下所示。 我認為從邏輯上講是正確的，但我認為它沒有正確實施。

當前的任務：以AAC格式記錄〜5秒的片段。

嘗試：使用AEAudioReciever回調並將AudioBufferList存儲在循環緩沖區中。 跟蹤記錄器類中已接收音頻的秒數； 一旦超過5秒標記（可能會稍稍超過6秒）。 調用Obj-c方法以使用AEAudioFileWriter寫入文件

結果：沒用，錄音聽起來很慢，並且不斷有很多噪音。 我可以聽到一些錄音的聲音； 所以我知道那里有一些數據，但是好像我正在丟失很多數據。 我什至不知道如何調試它（我將繼續嘗試，但此刻相當迷茫）。

另一個項目正在轉換為AAC，我是否首先以PCM格式寫入文件而不是轉換為AAC，還是可以僅將音頻段轉換為AAC？

謝謝您的幫助！

-----循環緩沖區初始化-----

//trying to get 5 seconds audio, how do I know what the length is if I don't know the frame size yet? and is that even the right question to ask?
TPCircularBufferInit(&_buffer, 1024 * 256);  

----- AEAudioReceiver回調------

static void receiverCallback(__unsafe_unretained MyAudioRecorder *THIS,
                         __unsafe_unretained AEAudioController *audioController,
                         void *source,
                         const AudioTimeStamp *time,
                         UInt32 frames,
                         AudioBufferList *audio) {
//store the audio into the buffer
TPCircularBufferCopyAudioBufferList(&THIS->_buffer, audio, time, kTPCircularBufferCopyAll, NULL);

//increase the time interval to track by THIS    
THIS.numberOfSecondInCurrentRecording += AEConvertFramesToSeconds(THIS.audioController, frames);

//if number of seconds passed an interval of 5 seconds, than write the last 5 seconds of the buffer to a file
if (THIS.numberOfSecondInCurrentRecording > 5 * THIS->_currentSegment + 1) {

    NSLog(@"Segment %d is full, writing file", THIS->_currentSegment);
    [THIS writeBufferToFile];

   //segment tracking variables
    THIS->_numberOfReceiverLoop = 0;
    THIS.lastTimeStamp = nil;
    THIS->_currentSegment += 1;
} else {
    THIS->_numberOfReceiverLoop += 1;
}

// Do something with 'audio'
if (!THIS.lastTimeStamp) {
    THIS.lastTimeStamp = (AudioTimeStamp *)time;
}
}

----寫入文件（MyAudioRecorderClass內部的方法）----

- (void)writeBufferToFileHandler {

NSString *documentsFolder = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)
                             objectAtIndex:0];

NSString *filePath = [documentsFolder stringByAppendingPathComponent:[NSString stringWithFormat:@"Segment_%d.aiff", _currentSegment]];

NSError *error = nil;

//setup audio writer, should the buffer be converted to aac first or save the file than convert; and how the heck do you do that?
AEAudioFileWriter *writeFile = [[AEAudioFileWriter alloc] initWithAudioDescription:_audioController.inputAudioDescription];
[writeFile beginWritingToFileAtPath:filePath fileType:kAudioFileAIFFType error:&error];

if (error) {
    NSLog(@"Error in init. the file: %@", error);
    return;
}

int i = 1;
//loop to write all the AudioBufferLists that is in the Circular Buffer; retrieve the ones based off of the _lastTimeStamp; but I had it in NULL too and worked the same way.
while (1) {

//NSLog(@"Processing buffer file list for segment [%d] and buffer index [%d]", _currentSegment, i);
    i += 1;
    // Discard any buffers with an incompatible format, in the event of a format change

    AudioBufferList *nextBuffer = TPCircularBufferNextBufferList(&_buffer, _lastTimeStamp);
    Float32 *frame = (Float32*) &nextBuffer->mBuffers[0].mData;

    //if buffer runs out, than we are done writing it and exit loop to close the file       
    if ( !nextBuffer ) {
        NSLog(@"Ran out of frames, there were [%d] AudioBufferList", i - 1);
        break;
    }
    //Adding audio using AudioFileWriter, is the length correct?
    OSStatus status = AEAudioFileWriterAddAudio(writeFile, nextBuffer, sizeof(nextBuffer->mBuffers[0].mDataByteSize));
    if (status) {
      NSLog(@"Writing Error? %d", status);
    }

    //consume/clear the buffer
    TPCircularBufferConsumeNextBufferList(&_buffer);
}

//close the file and hope it worked
[writeFile finishWriting];
}

-----音頻控制器AudioStreamBasicDescription ------

//interleaved16BitStereoAudioDescription
AudioStreamBasicDescription audioDescription;
memset(&audioDescription, 0, sizeof(audioDescription));
audioDescription.mFormatID          = kAudioFormatLinearPCM;
audioDescription.mFormatFlags       = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked | kAudioFormatFlagsNativeEndian;
audioDescription.mChannelsPerFrame  = 2;
audioDescription.mBytesPerPacket    = sizeof(SInt16)*audioDescription.mChannelsPerFrame;
audioDescription.mFramesPerPacket   = 1;
audioDescription.mBytesPerFrame     = sizeof(SInt16)*audioDescription.mChannelsPerFrame;
audioDescription.mBitsPerChannel    = 8 * sizeof(SInt16);
audioDescription.mSampleRate        = 44100.0;