如何使用AVAssetWriter在ios中寫入AAC音頻？

我正在使用AVCaptureSession從設備麥克風和攝像頭捕獲音頻和視頻樣本。如何使用AVAssetWriter在ios中寫入AAC音頻？

我再嘗試寫CMSampleBuffers（使用AVAssetWriter和AVAssetWriterInputs）通過AVCaptureSessions委託方法返回

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer: (CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection

這工作得很好，當我的聲音AVAssetWriterInput被配置爲將數據寫出來的蘋果無損格式（ kAudioFormatAppleLossless），但如果我嘗試和配置音頻AVAssetWriterInput使用AAC（kAudioFormatMPEG4AAC）它成功地寫入視頻和音頻樣本500ms左右，然後失敗，出現以下錯誤

writer has failed with Error Domain=AVFoundationErrorDomain Code=-11821 "Cannot Decode" UserInfo=0x4b2630 {NSLocalizedFailureReason=The media data could not be decoded. It may be damaged., NSUnderlyingError=0x4ad0f0 "The operation couldn’t be completed. (OSStatus error 560226676.)", NSLocalizedDescription=Cannot Decode}

這裏是我用來創建我AVAssetWriter代碼和AVAssetWriterInputs

NSError *error = nil; 
m_VideoCaputurePath = [[NSString stringWithFormat:@"%@/%@.mp4",[UserData getSavePath],[UserData getUniqueFilename]] retain]; 

if(USE_AAC_AUDIO) 
{ 
    m_audioAndVideoWriter = [[AVAssetWriter alloc] initWithURL:[NSURL fileURLWithPath:m_VideoCaputurePath] fileType:AVFileTypeMPEG4 error:&error]; 
} 
else 
{ 
    m_audioAndVideoWriter = [[AVAssetWriter alloc] initWithURL:[NSURL fileURLWithPath:m_VideoCaputurePath] fileType:AVFileTypeQuickTimeMovie error:&error]; 
} 

//\Configure Video Writer Input 
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys: 
           AVVideoCodecH264, AVVideoCodecKey, 
           [NSNumber numberWithInt:640], AVVideoWidthKey, 
           [NSNumber numberWithInt:480], AVVideoHeightKey, 
           nil]; 

m_videoWriterInput = [[AVAssetWriterInput 
         assetWriterInputWithMediaType:AVMediaTypeVideo 
         outputSettings:videoSettings] retain]; 

m_videoWriterInput.expectsMediaDataInRealTime = YES; 

//\Configure Audio Writer Input 

AudioChannelLayout acl; 
bzero(&acl, sizeof(acl)); 
acl.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo; 

NSDictionary* audioOutputSettings; 
if(USE_AAC_AUDIO) 
{ 
    audioOutputSettings = [ NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:kAudioFormatMPEG4AAC], AVFormatIDKey, 
              [ NSNumber numberWithInt: 1 ], AVNumberOfChannelsKey, 
              [ NSNumber numberWithFloat: 44100.0 ], AVSampleRateKey, 
              [ NSData dataWithBytes: &acl length: sizeof(acl) ], AVChannelLayoutKey, 
              [ NSNumber numberWithInt: 96 ], AVEncoderBitRateKey, 
              nil]; 
} 
else 
{ 
    audioOutputSettings = [ NSDictionary dictionaryWithObjectsAndKeys:      
              [ NSNumber numberWithInt: kAudioFormatAppleLossless ], AVFormatIDKey, 
              [ NSNumber numberWithInt: 16 ], AVEncoderBitDepthHintKey, 
              [ NSNumber numberWithFloat: 44100.0 ], AVSampleRateKey, 
              [ NSNumber numberWithInt: 1 ], AVNumberOfChannelsKey,          
              [ NSData dataWithBytes: &acl length: sizeof(acl) ], AVChannelLayoutKey, nil ]; 
} 

m_audioWriterInput = [[AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:audioOutputSettings] retain]; 

m_audioWriterInput.expectsMediaDataInRealTime = YES; 

//\Add inputs to Write 
NSAssert([m_audioAndVideoWriter canAddInput:m_audioWriterInput], @"Cannot write to this type of audio input"); 
NSAssert([m_audioAndVideoWriter canAddInput:m_videoWriterInput], @"Cannot write to this type of video input"); 

[m_audioAndVideoWriter addInput:m_videoWriterInput]; 
[m_audioAndVideoWriter addInput:m_audioWriterInput];

有誰知道如何正確地寫音頻採樣使用配置爲寫AAC的AVAssetWriterInput從AVCaptureSession回來了？

來源

2011-10-04 RyanSullivan

我設法得到它通過改變爲所需的輸出設置通過AVEncoderBitRateKey參數初始化能夠寫入AAC音頻的AVAssetWriterInput工作從96到64000

我的音效設置，現在看起來像

NSDictionary* audioOutputSettings = [NSDictionary dictionaryWithObjectsAndKeys: 
            [ NSNumber numberWithInt: kAudioFormatMPEG4AAC], AVFormatIDKey, 
            [ NSNumber numberWithInt: 1 ], AVNumberOfChannelsKey, 
            [ NSNumber numberWithFloat: 44100.0 ], AVSampleRateKey, 
            [ NSData dataWithBytes: &acl length: sizeof(AudioChannelLayout) ], AVChannelLayoutKey, 
            [ NSNumber numberWithInt: 64000 ], AVEncoderBitRateKey, 
            nil]

來源

2011-10-05 07:31:28 RyanSullivan

隨着新的iPhone 4s我不得不將AVNumberOfChannelsKey更改爲2 – RyanSullivan

我只是無法弄清楚這一點！我知道這與選擇有關，但不知道究竟是什麼。感謝你！ –

如何使用AVAssetWriter在ios中寫入AAC音頻？

回答

相關問題