A UIView subclass for recording the screen and saving as a file. Credit to Aroth from CodeThink. From this blog entry : http://aroth.no-ip.org:82/wordpress/archives/673

ScreenCaptureView.m

//
//ScreenCaptureView.h
//
#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
 
/**
 * Delegate protocol.  Implement this if you want to receive a notification when the
 * view completes a recording.
 *
 * When a recording is completed, the ScreenCaptureView will notify the delegate, passing
 * it the path to the created recording file if the recording was successful, or a value
 * of nil if the recording failed/could not be saved.
 */
@protocol ScreenCaptureViewDelegate <NSObject>
- (void) recordingFinished:(NSString*)outputPathOrNil;
@end
 
/**
 * ScreenCaptureView, a UIView subclass that periodically samples its current display
 * and stores it as a UIImage available through the 'currentScreen' property.  The
 * sample/update rate can be configured (within reason) by setting the 'frameRate'
 * property.
 *
 * This class can also be used to record real-time video of its subviews, using the
 * 'startRecording' and 'stopRecording' methods.  A new recording will overwrite any
 * previously made recording file, so if you want to create multiple recordings per
 * session (or across multiple sessions) then it is your responsibility to copy/back-up
 * the recording output file after each session.
 *
 * To use this class, you must link against the following frameworks:
 *
 *  - AssetsLibrary
 *  - AVFoundation
 *  - CoreGraphics
 *  - CoreMedia
 *  - CoreVideo
 *  - QuartzCore
 *
 */
 
@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
 
//
//ScreenCaptureView.m
//
#import "ScreenCaptureView.h"
#import <QuartzCore/QuartzCore.h>
#import <MobileCoreServices/UTCoreTypes.h>
#import <AssetsLibrary/AssetsLibrary.h>
 
@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,
                                    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 release];
   avAdaptor = nil;
 
   [videoWriterInput release];
   videoWriterInput = nil;
 
   [videoWriter release];
   videoWriter = nil;
 
   [startedAt release];
   startedAt = nil;
 
   if (bitmapData != NULL) {
       free(bitmapData);
       bitmapData = NULL;
   }
}
 
- (void)dealloc {
   [self cleanupWriter];
   [super dealloc];
}
 
- (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);
       }
   }
 
   [outputPath release];
   return [outputURL autorelease];
}
 
-(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] retain];
 
   NSParameterAssert(videoWriterInput);
   videoWriterInput.expectsMediaDataInRealTime = YES;
   NSDictionary* bufferAttributes = [NSDictionary dictionaryWithObjectsAndKeys:
                                     [NSNumber numberWithInt:kCVPixelFormatType_32ARGB], kCVPixelBufferPixelFormatTypeKey, nil];
 
   avAdaptor = [[AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:videoWriterInput sourcePixelBufferAttributes:bufferAttributes] retain];
 
   //add input
   [videoWriter addInput:videoWriterInput];
   [videoWriter startWriting];
   [videoWriter startSessionAtSourceTime:CMTimeMake(0, 1000)];
 
   return YES;
}
 
- (void) completeRecordingSession {
   NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
 
   [videoWriterInput markAsFinished];
 
   // Wait for the video
   int status = videoWriter.status;
   while (status == AVAssetWriterStatusUnknown) {
       NSLog(@"Waiting...");
       [NSThread sleepForTimeInterval:0.5f];
       status = videoWriter.status;
   }
 
   @synchronized(self) {
       BOOL success = [videoWriter finishWriting];
       if (!success) {
           NSLog(@"finishWriting returned NO");
       }
 
       [self cleanupWriter];
 
       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];
       }
 
       [outputPath release];
       [outputURL release];
   }
 
   [pool drain];
}
 
- (bool) startRecording {
   bool result = NO;
   @synchronized(self) {
       if (! _recording) {
           result = [self setUpWriter];
           startedAt = [[NSDate date] retain];
           _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 retain];
           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
           [newFrame release];
           CVPixelBufferUnlockBaseAddress( pixelBuffer, 0 );
           CVPixelBufferRelease( pixelBuffer );
           CFRelease(image);
           CGImageRelease(cgImage);
       }
 
   }
 
}
 
@end