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POThis code to write video+audio through AVAssetWriter and AVAssetWriterInputs is not working. Why?
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copied!<p>I've been trying to write a video+audio using AVAssetWriter and AVAssetWriterInputs.</p> <p>I read multiple posts in this forum of people saying they were able to accomplish that, but it is not working for me. If I just write video then the code is doing its job very well. When I add audio the output file is corrupted and cannot be reproduced.</p> <p>Here is part of my code:</p> <p>Setting up AVCaptureVideoDataOutput and AVCaptureAudioDataOutput:</p> <pre><code>NSError *error = nil; // Setup the video input AVCaptureDevice *videoDevice = [AVCaptureDevice defaultDeviceWithMediaType: AVMediaTypeVideo]; // Create a device input with the device and add it to the session. AVCaptureDeviceInput *videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error]; // Setup the video output _videoOutput = [[AVCaptureVideoDataOutput alloc] init]; _videoOutput.alwaysDiscardsLateVideoFrames = NO; _videoOutput.videoSettings = [NSDictionary dictionaryWithObject: [NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey]; // Setup the audio input AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType: AVMediaTypeAudio]; AVCaptureDeviceInput *audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:&error ]; // Setup the audio output _audioOutput = [[AVCaptureAudioDataOutput alloc] init]; // Create the session _capSession = [[AVCaptureSession alloc] init]; [_capSession addInput:videoInput]; [_capSession addInput:audioInput]; [_capSession addOutput:_videoOutput]; [_capSession addOutput:_audioOutput]; _capSession.sessionPreset = AVCaptureSessionPresetLow; // Setup the queue dispatch_queue_t queue = dispatch_queue_create("MyQueue", NULL); [_videoOutput setSampleBufferDelegate:self queue:queue]; [_audioOutput setSampleBufferDelegate:self queue:queue]; dispatch_release(queue); </code></pre> <p>Setting up AVAssetWriter and associating both audio and video AVAssetWriterInputs to it:</p> <pre><code>- (BOOL)setupWriter { NSError *error = nil; _videoWriter = [[AVAssetWriter alloc] initWithURL:videoURL fileType:AVFileTypeQuickTimeMovie error:&error]; NSParameterAssert(_videoWriter); // Add video input NSDictionary *videoCompressionProps = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithDouble:128.0*1024.0], AVVideoAverageBitRateKey, nil ]; NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys: AVVideoCodecH264, AVVideoCodecKey, [NSNumber numberWithInt:192], AVVideoWidthKey, [NSNumber numberWithInt:144], AVVideoHeightKey, videoCompressionProps, AVVideoCompressionPropertiesKey, nil]; _videoWriterInput = [[AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings] retain]; NSParameterAssert(_videoWriterInput); _videoWriterInput.expectsMediaDataInRealTime = YES; // Add the audio input AudioChannelLayout acl; bzero( &acl, sizeof(acl)); acl.mChannelLayoutTag = kAudioChannelLayoutTag_Mono; NSDictionary* audioOutputSettings = nil; // Both type of audio inputs causes output video file to be corrupted. if (NO) { // should work from iphone 3GS on and from ipod 3rd generation audioOutputSettings = [NSDictionary dictionaryWithObjectsAndKeys: [ NSNumber numberWithInt: kAudioFormatMPEG4AAC ], AVFormatIDKey, [ NSNumber numberWithInt: 1 ], AVNumberOfChannelsKey, [ NSNumber numberWithFloat: 44100.0 ], AVSampleRateKey, [ NSNumber numberWithInt: 64000 ], AVEncoderBitRateKey, [ NSData dataWithBytes: &acl length: sizeof( acl ) ], AVChannelLayoutKey, nil]; } else { // should work on any device requires more space 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 ]; } _audioWriterInput = [[AVAssetWriterInput assetWriterInputWithMediaType: AVMediaTypeAudio outputSettings: audioOutputSettings ] retain]; _audioWriterInput.expectsMediaDataInRealTime = YES; // add input [_videoWriter addInput:_videoWriterInput]; [_videoWriter addInput:_audioWriterInput]; return YES; } </code></pre> <p>here are functions to start/stop video recording</p> <pre><code>- (void)startVideoRecording { if (!_isRecording) { NSLog(@"start video recording..."); if (![self setupWriter]) { return; } _isRecording = YES; } } - (void)stopVideoRecording { if (_isRecording) { _isRecording = NO; [_videoWriterInput markAsFinished]; [_videoWriter endSessionAtSourceTime:lastSampleTime]; [_videoWriter finishWriting]; NSLog(@"video recording stopped"); } } </code></pre> <p>And finally the CaptureOutput code</p> <pre><code>- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection { if (!CMSampleBufferDataIsReady(sampleBuffer)) { NSLog( @"sample buffer is not ready. Skipping sample" ); return; } if (_isRecording == YES) { lastSampleTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer); if (_videoWriter.status != AVAssetWriterStatusWriting ) { [_videoWriter startWriting]; [_videoWriter startSessionAtSourceTime:lastSampleTime]; } if (captureOutput == _videoOutput) { [self newVideoSample:sampleBuffer]; } /* // If I add audio to the video, then the output file gets corrupted and it cannot be reproduced } else { [self newAudioSample:sampleBuffer]; } */ } } - (void)newVideoSample:(CMSampleBufferRef)sampleBuffer { if (_isRecording) { if (_videoWriter.status > AVAssetWriterStatusWriting) { NSLog(@"Warning: writer status is %d", _videoWriter.status); if (_videoWriter.status == AVAssetWriterStatusFailed) NSLog(@"Error: %@", _videoWriter.error); return; } if (![_videoWriterInput appendSampleBuffer:sampleBuffer]) { NSLog(@"Unable to write to video input"); } } } - (void)newAudioSample:(CMSampleBufferRef)sampleBuffer { if (_isRecording) { if (_videoWriter.status > AVAssetWriterStatusWriting) { NSLog(@"Warning: writer status is %d", _videoWriter.status); if (_videoWriter.status == AVAssetWriterStatusFailed) NSLog(@"Error: %@", _videoWriter.error); return; } if (![_audioWriterInput appendSampleBuffer:sampleBuffer]) { NSLog(@"Unable to write to audio input"); } } } </code></pre> <p>I would be very glad if someone could find which is the problem in this code.</p>

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