经过长时间的研究，我有一个应用程序的代码，即使你从前置摄像头切换到后置摄像头，仍然可以捕捉视频，反之亦然：
#import "ViewController.h"
#import <AssetsLibrary/AssetsLibrary.h>
#import <MediaPlayer/MediaPlayer.h>
#import <Photos/Photos.h>
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
currentFrontCamera=NO;
isCapturingInput=NO;
_assetWriter=nil;
[self findCamera:YES]; // init the front camera
[self findCamera:NO]; // init the back camera
[self performSelector:@selector(initCaptureWithCamera) withObject:nil afterDelay:1];
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
-(IBAction)tapStartRecord:(id)sender
{
if([[btnRecord titleForState:UIControlStateNormal] isEqualToString:@"START"])
{
[btnRecord setTitle:@"STOP" forState:UIControlStateNormal];
isCapturingInput=YES;
}
else if([[btnRecord titleForState:UIControlStateNormal] isEqualToString:@"STOP"])
{
isCapturingInput=NO;
dispatch_async(_captureQueue, ^{
[_assetWriter finishWritingWithCompletionHandler:^{
// Save to the album
__block PHObjectPlaceholder *placeholder;
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
PHAssetChangeRequest* createAssetRequest = [PHAssetChangeRequest creationRequestForAssetFromVideoAtFileURL:recordingFile];
placeholder = [createAssetRequest placeholderForCreatedAsset];
} completionHandler:^(BOOL success, NSError *error) {
if (success)
{
NSLog(@"Video successfully saved!");
}
else
{
NSLog(@"%@", error);
}
[self.captureSession stopRunning];
_assetWriter=nil;
recordingFile = nil;
}];
}];
});
[btnRecord setTitle:@"START" forState:UIControlStateNormal];
}
}
-(IBAction)tapSwitchCamera:(id)sender
{
// switch outputs
[self swipeCamera];
}
-(void)swipeCamera
{
currentFrontCamera=!currentFrontCamera; // swipe camera
[self.captureSession beginConfiguration];
[self.captureSession removeInput:captureBackInput];
[self.captureSession removeInput:captureFrontInput];
if(!currentFrontCamera)
[self.captureSession addInput:captureBackInput];
else
[self.captureSession addInput:captureFrontInput];
[self.captureSession commitConfiguration];
}
#pragma mark - Camera methods
-(BOOL)findCamera:(BOOL)useFrontCamera
{
// 0. Make sure we initialize our camera pointer:
AVCaptureDevice *m_camera = NULL;
// 1. Get a list of available devices:
// specifying AVMediaTypeVideo will ensure we only get a list of cameras, no microphones
NSArray * devices = [ AVCaptureDevice devicesWithMediaType: AVMediaTypeVideo ];
// 2. Iterate through the device array and if a device is a camera, check if it's the one we want:
for ( AVCaptureDevice * device in devices )
{
if ( useFrontCamera && AVCaptureDevicePositionFront == [ device position ] )
{
// We asked for the front camera and got the front camera, now keep a pointer to it:
m_camera = device;
}
else if ( !useFrontCamera && AVCaptureDevicePositionBack == [ device position ] )
{
// We asked for the back camera and here it is:
m_camera = device;
}
}
// 3. Set a frame rate for the camera:
if ( NULL != m_camera )
{
// We firt need to lock the camera, so noone else can mess with its configuration:
if ( [ m_camera lockForConfiguration: NULL ] )
{
// Set a minimum frame rate of 10 frames per second
[ m_camera setActiveVideoMinFrameDuration: CMTimeMake( 1, 10 ) ];
// and a maximum of 30 frames per second
[ m_camera setActiveVideoMaxFrameDuration: CMTimeMake( 1, 30 ) ];
[ m_camera unlockForConfiguration ];
}
}
if(!useFrontCamera)
backCamera=m_camera;
else
frontCamera=m_camera;
// 4. If we've found the camera we want, return true
return ( NULL != m_camera );
}
-(void) setupWriter
{
NSError *error = nil;
_assetWriter = [[AVAssetWriter alloc] initWithURL:recordingFile fileType:AVFileTypeQuickTimeMovie error:&error];
NSDictionary* actual = videoOutput.videoSettings;
int _cy = [[actual objectForKey:@"Height"] intValue];
int _cx = [[actual objectForKey:@"Width"] intValue];
NSDictionary* settings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
[NSNumber numberWithInt: _cx], AVVideoWidthKey,
[NSNumber numberWithInt: _cy], AVVideoHeightKey,
nil];
_videoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:settings];
_videoWriterInput.expectsMediaDataInRealTime = YES;
_videoWriterInput.transform=CGAffineTransformMakeRotation(M_PI/2); // else it will shot in landscape even though we hold our phone in portrait mode
/*settings = [NSDictionary dictionaryWithObjectsAndKeys:
[ NSNumber numberWithInt: kAudioFormatMPEG4AAC], AVFormatIDKey,
[ NSNumber numberWithInt: 1], AVNumberOfChannelsKey,
[ NSNumber numberWithFloat: 16000], AVSampleRateKey,
[ NSNumber numberWithInt: 64000 ], AVEncoderBitRateKey,
nil];*/
_audioWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType: AVMediaTypeAudio outputSettings: nil];
_audioWriterInput.expectsMediaDataInRealTime = YES;
// add input
if([_assetWriter canAddInput:_videoWriterInput])
{
NSLog(@"added output to video");
[_assetWriter addInput:_videoWriterInput];
}
if([_assetWriter canAddInput:_audioWriterInput])
{
NSLog(@"added output to audio");
[_assetWriter addInput:_audioWriterInput];
}
}
- (void)initCaptureWithCamera
{
if(self.captureVideoPreviewLayer!=nil) // refresh the views
[self.captureVideoPreviewLayer removeFromSuperlayer];
// remove old file at path if exists
recordingFile = [NSURL fileURLWithPath:[NSString stringWithFormat:@"%@/tmp_vid.mov", NSTemporaryDirectory()]];
[[NSFileManager defaultManager] removeItemAtURL:recordingFile error:nil];
// ========================= configure session
self.captureSession = [[AVCaptureSession alloc] init];
NSString* preset = 0;
if (!preset) {
preset = AVCaptureSessionPresetHigh;
}
self.captureSession.sessionPreset = preset;
// ========================= input devices from camera and mic
NSError * error = NULL;
captureFrontInput = [AVCaptureDeviceInput deviceInputWithDevice:frontCamera error: &error];
captureBackInput = [AVCaptureDeviceInput deviceInputWithDevice:backCamera error: &error];
if ( NULL != error )
return;
if ([self.captureSession canAddInput:captureBackInput])
{
NSLog(@"added input from camera");
[self.captureSession addInput:captureBackInput];
}
// audio input from default mic
AVCaptureDevice* mic = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
AVCaptureDeviceInput* micinput = [AVCaptureDeviceInput deviceInputWithDevice:mic error:nil];
if ([self.captureSession canAddInput:micinput])
{
NSLog(@"added input from mic");
[self.captureSession addInput:micinput];
}
// ========================= now output forms: video and audio in asset writter
_captureQueue = dispatch_queue_create("com.myapp.capture", DISPATCH_QUEUE_SERIAL);
videoOutput = [[AVCaptureVideoDataOutput alloc] init];
AVCaptureAudioDataOutput *audioOutput = [[AVCaptureAudioDataOutput alloc] init];
[videoOutput setSampleBufferDelegate:self queue:_captureQueue];
[audioOutput setSampleBufferDelegate:self queue:_captureQueue];
// NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey;
// NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA];
// NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:value forKey:key];
//
// [videoOutput setVideoSettings:videoSettings];
if ([self.captureSession canAddOutput:videoOutput]) {
[self.captureSession addOutput:videoOutput];
}
if ([self.captureSession canAddOutput:audioOutput]) {
[self.captureSession addOutput:audioOutput];
}
// add the preview layer to see what we film
if (!self.captureVideoPreviewLayer)
self.captureVideoPreviewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.captureSession];
// if you want to adjust the previewlayer frame, here!
self.captureVideoPreviewLayer.frame = viewCanvasRecording.bounds;
self.captureVideoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
[viewCanvasRecording.layer addSublayer: self.captureVideoPreviewLayer];
[self.captureSession startRunning];
}
-(void)captureOutput:(AVCaptureOutput*)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection*)connection
{
BOOL frameFromVideoCaptured = NO;
@synchronized(self)
{
if (!isCapturingInput) // we haven't started filming yet just ignore the frames
return;
if(!_assetWriter)
{
[self setupWriter];
}
frameFromVideoCaptured=(captureOutput==videoOutput);
}
// pass frame to the assset writer
[self writeFrame:sampleBuffer isVideo:frameFromVideoCaptured];
}
-(BOOL)writeFrame:(CMSampleBufferRef)sampleBuffer isVideo:(BOOL)isVideo
{
if (CMSampleBufferDataIsReady(sampleBuffer))
{
if (_assetWriter.status == AVAssetWriterStatusUnknown)
{
CMTime startTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
[_assetWriter startWriting];
[_assetWriter startSessionAtSourceTime:startTime];
}
if (_assetWriter.status == AVAssetWriterStatusFailed)
{
NSLog(@"writer error %@", _assetWriter.error.localizedDescription);
return NO;
}
if (isVideo)
{
if (_videoWriterInput.readyForMoreMediaData == YES)
{
[_videoWriterInput appendSampleBuffer:sampleBuffer];
return YES;
}
}
else
{
if (_audioWriterInput.readyForMoreMediaData)
{
[_audioWriterInput appendSampleBuffer:sampleBuffer];
return YES;
}
}
}
return NO;
}
@end
但问题是每当我按下＆＃34; STOP＆＃34;按钮，视频已保存，但应用程序冻结，当我尝试创建另一个会话时，应用程序崩溃任何帮助将非常感谢，谢谢。