问题
How can I record on the iOS 8 or even iOS 7 (if possible) and switch between cameras while I do so? I have seen apps doing this recording from front camera and then switching to back camera and when the film is completed you can see it entirely filmed from both cameras? I think Glide app has it and maybe Snapchat (not sure on the last one)
回答1:
After long searches and struggles, here is the code... thanks for your suggestion Matic for pointing me to the right path, I have made something a little better, without actually merging files at the end
#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
#import <CoreGraphics/CoreGraphics.h>
@interface ViewController : UIViewController <AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureAudioDataOutputSampleBufferDelegate>
{
IBOutlet UIView *viewCanvasRecording;
IBOutlet UIButton *btnRecord;
AVCaptureDevice *frontCamera; // A pointer to the front camera
AVCaptureDevice *backCamera; // A pointer to the back camera
AVCaptureDeviceInput *captureFrontInput;
AVCaptureDeviceInput *captureBackInput;
__block AVAssetWriter *_assetWriter;
__block AVAssetWriterInput *_videoWriterInput;
__block AVAssetWriterInput *_audioWriterInput;
__block AVCaptureVideoDataOutput *videoOutput;
dispatch_queue_t _captureQueue;
BOOL currentFrontCamera;
BOOL isCapturingInput;
NSURL *recordingFile;
}
@property (nonatomic, strong) AVCaptureSession *captureSession;
@property (nonatomic, strong) AVCaptureVideoPreviewLayer *captureVideoPreviewLayer;
@end
// ===== now the m file
//
// ViewController.m
// record
//
// Created by Catalin on 31/05/15.
// Copyright (c) 2015 lamobratory.com. All rights reserved.
//
#import "ViewController.h"
#import <AssetsLibrary/AssetsLibrary.h>
#import <MediaPlayer/MediaPlayer.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:^{
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
[library writeVideoAtPathToSavedPhotosAlbum:recordingFile completionBlock:^(NSURL *assetURL, NSError *error)
{
if (error)
{
NSLog(@"assets library failed (%@)", error);
}
else
{
NSLog(@"file saved to library");
}
[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
回答2:
I am using a multi file procedure. On swap I remove the inputs and the outputs on the capture session and reattach the new output (AVCaptureMovieFileOutput) and attach the correct input. On continuing the recording the AVCaptureMovieFileOutput gets a different file name then the previous had so I actually create a series of files. Also note AVCaptureMovieFileOutput must be a new object, you may not reuse the previous one as it most likely hadn't stopped writing yet. The inputs are reused though.
After all is done there are various ways of stitching the videos together depending on the level you need to work on.
So my basic components are AVCaptureSession, AVCaptureMovieFileOutput and AVCaptureDeviceInput. Also a AVCaptureVideoPreviewLayer is attached to see what you are recording.
来源：https://stackoverflow.com/questions/30499781/ios-8-film-from-both-back-and-front-camera