[Iphone] Questo codice per scrivere video + audio tramite AVAssetWriter e AVAssetWriterInputs non funziona. Perché?


Answers

Innanzitutto, non utilizzare [NSNumber numberWithInt: kCVPixelFormatType_32BGRA], in quanto non è il formato nativo della videocamera. usa [NSNumber numberWithInt: kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange]

Inoltre, dovresti sempre controllare prima di chiamare startWriting che non è già in esecuzione. Non è necessario impostare l'ora di fine della sessione, poiché stopWriting lo farà.

Question

Ho provato a scrivere un video + audio usando AVAssetWriter e AVAssetWriterInputs.

Ho letto più post in questo forum di persone dicendo che erano in grado di farlo, ma non funziona per me. Se scrivo solo video, il codice sta facendo il suo lavoro molto bene. Quando aggiungo l'audio, il file di output è danneggiato e non può essere riprodotto.

Ecco parte del mio codice:

Configurazione di AVCaptureVideoDataOutput e AVCaptureAudioDataOutput:

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);

Configurare AVAssetWriter e associare ad esso sia AVAssetWriterInputs audio e video:

- (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;
}

qui ci sono funzioni per avviare / fermare la registrazione video

- (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");
    }
}

E infine il codice CaptureOutput

- (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");
        }
    }
}

Sarei molto felice se qualcuno potesse scoprire qual è il problema in questo codice.