ios - 在写入磁盘之前，在录制时将 CATextLayer Overlay 写入 AVCaptureSession

Question

我试图在通过 AVCaptureSession 记录到磁盘时以 CATextLayer 的形式编写时间码。这是我到目前为止的代码，我无法在文档中找到任何内容，也无法通过谷歌向我展示这是如何实现的。

最初我使用 GPUImage 完成此操作，但代码不稳定且崩溃。库的作者确认 GPUImage 目前不能可靠地用于此目的。

CaptureSessionManager.h

#import <CoreMedia/CoreMedia.h>
#import <AVFoundation/AVFoundation.h>


@interface CaptureSessionManager:NSObject

@property (nonatomic,strong) AVCaptureVideoPreviewLayer *previewLayer;
@property (nonatomic,strong) AVCaptureSession *captureSession;
@property (nonatomic,strong) AVCaptureMovieFileOutput *captureOutput;
@property (nonatomic,strong) AVCaptureDeviceInput *videoIn;

- (void)addVideoPreviewLayer;
- (void)addVideoInput;
- (void)addVideoOutput;
- (void)toggleDeviceCamera;

- (void)toggleRecording;

@end

CaptureSessionManager.m

#import "CaptureSessionManager.h"
#import <CoreMedia/CoreMedia.h>
#import <AVFoundation/AVFoundation.h>
#import <AssetsLibrary/AssetsLibrary.h>
#import <QuartzCore/QuartzCore.h>
#import <CoreVideo/CoreVideo.h>

#define CAPTURE_FRAMES_PER_SECOND       20

@interface CaptureSessionManager() <AVCaptureFileOutputRecordingDelegate,
                                    AVCaptureVideoDataOutputSampleBufferDelegate> {
    BOOL isRecording;
}
@end

@implementation CaptureSessionManager
@synthesize captureSession;
@synthesize previewLayer;
@synthesize captureOutput;
@synthesize videoIn;

#pragma mark Capture Session Configuration

- (id)init {
    if ((self = [super init])) {
        [self setCaptureSession:[[AVCaptureSession alloc] init]];
    }
    return self;
}

- (void)addVideoPreviewLayer {
    [self setPreviewLayer:[[[AVCaptureVideoPreviewLayer alloc] initWithSession:[self captureSession]] autorelease]];
    [[self previewLayer] setVideoGravity:AVLayerVideoGravityResizeAspectFill];

}

- (void)addVideoInput {
    AVCaptureDevice *videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    if (videoDevice) {
        NSError *error;
        if ([videoDevice isFocusModeSupported:AVCaptureFocusModeContinuousAutoFocus] &&
            [videoDevice lockForConfiguration:&error]) {
            [videoDevice setFocusMode:AVCaptureFocusModeContinuousAutoFocus];
            [videoDevice unlockForConfiguration];
        }
        videoIn = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:&error];
        if (!error) {
            if ([[self captureSession] canAddInput:videoIn]) {
                [[self captureSession] addInput:videoIn];

            } else
                NSLog(@"Couldn't add video input");
        }
        else
            NSLog(@"Couldn't create video input");
    }
    else
        NSLog(@"Couldn't create video capture device");
}

- (void)addVideoOutput {
    //ADD MOVIE FILE OUTPUT
    NSLog(@"Adding movie file output");
    captureOutput = [[AVCaptureMovieFileOutput alloc] init];

    Float64 TotalSeconds = 60;          //Total seconds
    int32_t preferredTimeScale = 30;    //Frames per second
    CMTime maxDuration = CMTimeMakeWithSeconds(TotalSeconds, preferredTimeScale);   //<<SET MAX DURATION
    captureOutput.maxRecordedDuration = maxDuration;
    captureOutput.minFreeDiskSpaceLimit = 1024 * 1024;                      //<<SET MIN FREE SPACE IN BYTES FOR RECORDING TO CONTINUE ON A VOLUME

    if ([self.captureSession canAddOutput:captureOutput])
        [self.captureSession addOutput:captureOutput];

    //SET THE CONNECTION PROPERTIES (output properties)
    [self CameraSetOutputProperties];           //(We call a method as it also has to be done after changing camera)

    [self.captureSession setSessionPreset:AVCaptureSessionPresetMedium];
}

- (void) CameraSetOutputProperties
{
    //SET THE CONNECTION PROPERTIES (output properties)
    AVCaptureConnection *CaptureConnection = [captureOutput connectionWithMediaType:AVMediaTypeVideo];
}

- (void)toggleDeviceCamera
{
    if ([[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] count] > 1)        //Only do if device has multiple cameras
    {
        NSLog(@"Toggle camera");
        NSError *error;
        //AVCaptureDeviceInput *videoInput = [self videoInput];
        AVCaptureDeviceInput *NewVideoInput;
        AVCaptureDevicePosition position = [[videoIn device] position];
        if (position == AVCaptureDevicePositionBack)
        {
            NewVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self CameraWithPosition:AVCaptureDevicePositionFront] error:&error];
        }
        else if (position == AVCaptureDevicePositionFront)
        {
            NewVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self CameraWithPosition:AVCaptureDevicePositionBack] error:&error];
        }

        if (NewVideoInput != nil)
        {
            [self.captureSession beginConfiguration];       //We can now change the inputs and output configuration.  Use commitConfiguration to end
            [self.captureSession removeInput:videoIn];
            if ([self.captureSession canAddInput:NewVideoInput])
            {
                [self.captureSession addInput:NewVideoInput];
                videoIn = NewVideoInput;
            }
            else
            {
                [self.captureSession addInput:videoIn];
            }

            //Set the connection properties again
            [self CameraSetOutputProperties];


            [self.captureSession commitConfiguration];
            [NewVideoInput release];
        }
    }
}

//********** START STOP RECORDING BUTTON **********
- (void)toggleRecording {

    if (!isRecording)
    {
        //----- START RECORDING -----
        NSLog(@"START RECORDING");
        isRecording = YES;

        //Create temporary URL to record to
        NSString *outputPath = [[NSString alloc] initWithFormat:@"%@%@", NSTemporaryDirectory(), @"output.mov"];
        NSURL *outputURL = [[NSURL alloc] initFileURLWithPath:outputPath];
        NSFileManager *fileManager = [NSFileManager defaultManager];
        if ([fileManager fileExistsAtPath:outputPath])
        {
            NSError *error;
            if ([fileManager removeItemAtPath:outputPath error:&error] == NO)
            {
                //Error - handle if requried
            }
        }
        //Start recording
        [captureOutput startRecordingToOutputFileURL:outputURL recordingDelegate:self];
    }
    else
    {
        //----- STOP RECORDING -----
        NSLog(@"STOP RECORDING");
        isRecording = NO;

        [captureOutput stopRecording];
    }
}

- (AVCaptureDevice *) CameraWithPosition:(AVCaptureDevicePosition) Position
{
    NSArray *Devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *Device in Devices)
    {
        if ([Device position] == Position)
        {
            return Device;
        }
    }
    return nil;
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    NSLog(@"a");
}

//********** DID FINISH RECORDING TO OUTPUT FILE AT URL **********
- (void)captureOutput:(AVCaptureFileOutput *)captureOutput
didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL
      fromConnections:(NSArray *)connections
                error:(NSError *)error
{

    NSLog(@"didFinishRecordingToOutputFileAtURL - enter");

    BOOL RecordedSuccessfully = YES;
    if ([error code] != noErr)
    {
        // A problem occurred: Find out if the recording was successful.
        id value = [[error userInfo] objectForKey:AVErrorRecordingSuccessfullyFinishedKey];
        if (value)
        {
            RecordedSuccessfully = [value boolValue];
        }
    }
    if (RecordedSuccessfully)
    {
        //----- RECORDED SUCESSFULLY -----
        NSLog(@"didFinishRecordingToOutputFileAtURL - success");
        ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
        if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:outputFileURL])
        {
            [library writeVideoAtPathToSavedPhotosAlbum:outputFileURL
                                        completionBlock:^(NSURL *assetURL, NSError *error)
             {
                 if (error)
                 {

                 }
             }];
        }
    }
}

- (void)dealloc {
    [super dealloc];
}

@end

Answer 1

好吧，我能够得到我的解决方案，我真诚地希望这对某人有所帮助。要获得用于录制视频、音频和写入磁盘的基本 AVFoundation 设置，请从 Apple 下载 RosyWriter https://developer.apple.com/library/prerelease/ios/samplecode/RosyWriter/RosyWriter.zip

之后，只需访问提供的渲染器之一。我强烈建议使用 OpenGL 渲染器。您将需要加强 UIView 绘图，但这将使您完成 90% 的工作!