【发布时间】：2015-06-15 14:48:25
【问题描述】：
我从这个 SO 问题 Screen capture video in iOS programmatically 中找到了本教程 http://codethink.no-ip.org/wordpress/archives/673#comment-118063 如何做这样的事情，它对于 iOS 来说有点过时了，所以我更新了它，并且非常接近它的工作，但是把UIImages 一起现在还不能很好地工作。
这是我在 viewDidLoad 中调用方法的方式
[captureView performSelector:@selector(startRecording) withObject:nil afterDelay:1.0];
[captureView performSelector:@selector(stopRecording) withObject:nil afterDelay:5.0];
captureView 是一个连接到我的视图的 IBOutlet。
然后我有类 ScreenCapture.h & .m
这里是.h
@protocol ScreenCaptureViewDelegate <NSObject>
- (void) recordingFinished:(NSString*)outputPathOrNil;
@end
@interface ScreenCaptureView : UIView {
//video writing
AVAssetWriter *videoWriter;
AVAssetWriterInput *videoWriterInput;
AVAssetWriterInputPixelBufferAdaptor *avAdaptor;
//recording state
BOOL _recording;
NSDate* startedAt;
void* bitmapData;
}
//for recording video
- (bool) startRecording;
- (void) stopRecording;
//for accessing the current screen and adjusting the capture rate, etc.
@property(retain) UIImage* currentScreen;
@property(assign) float frameRate;
@property(nonatomic, assign) id<ScreenCaptureViewDelegate> delegate;
@end
这是我的 .m
@interface ScreenCaptureView(Private)
- (void) writeVideoFrameAtTime:(CMTime)time;
@end
@implementation ScreenCaptureView
@synthesize currentScreen, frameRate, delegate;
- (void) initialize {
// Initialization code
self.clearsContextBeforeDrawing = YES;
self.currentScreen = nil;
self.frameRate = 10.0f; //10 frames per seconds
_recording = false;
videoWriter = nil;
videoWriterInput = nil;
avAdaptor = nil;
startedAt = nil;
bitmapData = NULL;
}
- (id) initWithCoder:(NSCoder *)aDecoder {
self = [super initWithCoder:aDecoder];
if (self) {
[self initialize];
}
return self;
}
- (id) init {
self = [super init];
if (self) {
[self initialize];
}
return self;
}
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
[self initialize];
}
return self;
}
- (CGContextRef) createBitmapContextOfSize:(CGSize) size {
CGContextRef context = NULL;
CGColorSpaceRef colorSpace;
int bitmapByteCount;
int bitmapBytesPerRow;
bitmapBytesPerRow = (size.width * 4);
bitmapByteCount = (bitmapBytesPerRow * size.height);
colorSpace = CGColorSpaceCreateDeviceRGB();
if (bitmapData != NULL) {
free(bitmapData);
}
bitmapData = malloc( bitmapByteCount );
if (bitmapData == NULL) {
fprintf (stderr, "Memory not allocated!");
return NULL;
}
context = CGBitmapContextCreate (bitmapData,
size.width,
size.height,
8, // bits per component
bitmapBytesPerRow,
colorSpace,
(CGBitmapInfo) kCGImageAlphaNoneSkipFirst);
CGContextSetAllowsAntialiasing(context,NO);
if (context== NULL) {
free (bitmapData);
fprintf (stderr, "Context not created!");
return NULL;
}
CGColorSpaceRelease( colorSpace );
return context;
}
static int frameCount = 0; //debugging
- (void) drawRect:(CGRect)rect {
NSDate* start = [NSDate date];
CGContextRef context = [self createBitmapContextOfSize:self.frame.size];
//not sure why this is necessary...image renders upside-down and mirrored
CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, self.frame.size.height);
CGContextConcatCTM(context, flipVertical);
[self.layer renderInContext:context];
CGImageRef cgImage = CGBitmapContextCreateImage(context);
UIImage* background = [UIImage imageWithCGImage: cgImage];
CGImageRelease(cgImage);
self.currentScreen = background;
//debugging
if (frameCount < 40) {
NSString* filename = [NSString stringWithFormat:@"Documents/frame_%d.png", frameCount];
NSString* pngPath = [NSHomeDirectory() stringByAppendingPathComponent:filename];
[UIImagePNGRepresentation(self.currentScreen) writeToFile: pngPath atomically: YES];
frameCount++;
}
//NOTE: to record a scrollview while it is scrolling you need to implement your UIScrollViewDelegate such that it calls
// 'setNeedsDisplay' on the ScreenCaptureView.
if (_recording) {
float millisElapsed = [[NSDate date] timeIntervalSinceDate:startedAt] * 1000.0;
[self writeVideoFrameAtTime:CMTimeMake((int)millisElapsed, 1000)];
}
float processingSeconds = [[NSDate date] timeIntervalSinceDate:start];
float delayRemaining = (1.0 / self.frameRate) - processingSeconds;
CGContextRelease(context);
//redraw at the specified framerate
[self performSelector:@selector(setNeedsDisplay) withObject:nil afterDelay:delayRemaining > 0.0 ? delayRemaining : 0.01];
}
- (void) cleanupWriter {
avAdaptor = nil;
videoWriterInput = nil;
videoWriter = nil;
startedAt = nil;
if (bitmapData != NULL) {
free(bitmapData);
bitmapData = NULL;
}
}
- (void)dealloc {
[self cleanupWriter];
}
- (NSURL*) tempFileURL {
NSString* outputPath = [[NSString alloc] initWithFormat:@"%@/%@", [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0], @"output.mp4"];
NSURL* outputURL = [[NSURL alloc] initFileURLWithPath:outputPath];
NSFileManager* fileManager = [NSFileManager defaultManager];
if ([fileManager fileExistsAtPath:outputPath]) {
NSError* error;
if ([fileManager removeItemAtPath:outputPath error:&error] == NO) {
NSLog(@"Could not delete old recording file at path: %@", outputPath);
}
}
return outputURL;
}
-(BOOL) setUpWriter {
NSError* error = nil;
videoWriter = [[AVAssetWriter alloc] initWithURL:[self tempFileURL] fileType:AVFileTypeQuickTimeMovie error:&error];
NSParameterAssert(videoWriter);
//Configure video
NSDictionary* videoCompressionProps = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithDouble:1024.0*1024.0], AVVideoAverageBitRateKey,
nil ];
NSDictionary* videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
[NSNumber numberWithInt:self.frame.size.width], AVVideoWidthKey,
[NSNumber numberWithInt:self.frame.size.height], AVVideoHeightKey,
videoCompressionProps, AVVideoCompressionPropertiesKey,
nil];
videoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];
NSParameterAssert(videoWriterInput);
videoWriterInput.expectsMediaDataInRealTime = YES;
NSDictionary* bufferAttributes = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithInt:kCVPixelFormatType_32ARGB], kCVPixelBufferPixelFormatTypeKey, nil];
avAdaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:videoWriterInput sourcePixelBufferAttributes:bufferAttributes];
//add input
[videoWriter addInput:videoWriterInput];
[videoWriter startWriting];
[videoWriter startSessionAtSourceTime:CMTimeMake(0, 1000)];
return YES;
}
- (void) completeRecordingSession {
[videoWriterInput markAsFinished];
// Wait for the video
int status = videoWriter.status;
while (status == AVAssetWriterStatusUnknown) {
NSLog(@"Waiting...");
[NSThread sleepForTimeInterval:0.5f];
status = videoWriter.status;
}
@synchronized(self) {
[videoWriter finishWritingWithCompletionHandler:^{
[self cleanupWriter];
BOOL success = YES;
id delegateObj = self.delegate;
NSString *outputPath = [[NSString alloc] initWithFormat:@"%@/%@", [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0], @"output.mp4"];
NSURL *outputURL = [[NSURL alloc] initFileURLWithPath:outputPath];
NSLog(@"Completed recording, file is stored at: %@", outputURL);
if ([delegateObj respondsToSelector:@selector(recordingFinished:)]) {
[delegateObj performSelectorOnMainThread:@selector(recordingFinished:) withObject:(success ? outputURL : nil) waitUntilDone:YES];
}
}];
}
}
- (bool) startRecording {
bool result = NO;
@synchronized(self) {
if (! _recording) {
result = [self setUpWriter];
startedAt = [NSDate date];
_recording = true;
}
}
return result;
}
- (void) stopRecording {
@synchronized(self) {
if (_recording) {
_recording = false;
[self completeRecordingSession];
}
}
}
-(void) writeVideoFrameAtTime:(CMTime)time {
if (![videoWriterInput isReadyForMoreMediaData]) {
NSLog(@"Not ready for video data");
}
else {
@synchronized (self) {
UIImage *newFrame = self.currentScreen;
CVPixelBufferRef pixelBuffer = NULL;
CGImageRef cgImage = CGImageCreateCopy([newFrame CGImage]);
CFDataRef image = CGDataProviderCopyData(CGImageGetDataProvider(cgImage));
int status = CVPixelBufferPoolCreatePixelBuffer(kCFAllocatorDefault, avAdaptor.pixelBufferPool, &pixelBuffer);
if(status != 0){
//could not get a buffer from the pool
NSLog(@"Error creating pixel buffer: status=%d", status);
}
// set image data into pixel buffer
CVPixelBufferLockBaseAddress( pixelBuffer, 0 );
uint8_t *destPixels = CVPixelBufferGetBaseAddress(pixelBuffer);
CFDataGetBytes(image, CFRangeMake(0, CFDataGetLength(image)), destPixels); //XXX: will work if the pixel buffer is contiguous and has the same bytesPerRow as the input data
if(status == 0){
BOOL success = [avAdaptor appendPixelBuffer:pixelBuffer withPresentationTime:time];
if (!success)
NSLog(@"Warning: Unable to write buffer to video");
}
//clean up
CVPixelBufferUnlockBaseAddress( pixelBuffer, 0 );
CVPixelBufferRelease( pixelBuffer );
CFRelease(image);
CGImageRelease(cgImage);
}
}
}
正如您在drawRect 方法中看到的那样，我保存了所有图像，它们看起来很棒，但是当我尝试制作视频时，它只会创建一个看起来像这样的静止图像，当图像看起来像这样。
这是输出，它是一个视频，但仅此而已。当图片看起来正常时（不倾斜，很奇怪）
我的问题是制作视频时出了什么问题？
感谢您的帮助和您的时间，我知道这是一个很长的问题。
【问题讨论】：
-
你为什么不更新你之前的问题（stackoverflow.com/questions/29551216/…）？
-
@rmaddy 抱歉，我本来想删除那个的，结果删了
标签： ios objective-c video avfoundation