How to make a movie from set of images using UIGetScreenImage - iphone

Question

I have used this method and get multiple images. I am able to successfully create a movie but my problem is that when I play the movie, it seems to be playing too fast i.e. the movie doesn't have all the frames. Here is my code.
-(UIImage *)uiImageScreen
{
CGImageRef screen = UIGetScreenImage();
UIImage* image = [UIImage imageWithCGImage:screen];
CGImageRelease(screen);
UIImageWriteToSavedPhotosAlbum(image, self,nil, nil);
return image;
}
-(void) writeSample: (NSTimer*) _timer
{
if (assetWriterInput.readyForMoreMediaData) {
// CMSampleBufferRef sample = nil;
CVReturn cvErr = kCVReturnSuccess;
// get screenshot image!
CGImageRef image = (CGImageRef) [[self uiImageScreen] CGImage];
NSLog (#"made screenshot");
// prepare the pixel buffer
CVPixelBufferRef pixelBuffer = NULL;
CFDataRef imageData= CGDataProviderCopyData(CGImageGetDataProvider(image));
NSLog (#"copied image data");
cvErr = CVPixelBufferCreateWithBytes(kCFAllocatorDefault,
FRAME_WIDTH,
FRAME_HEIGHT,
kCVPixelFormatType_32BGRA,
(void*)CFDataGetBytePtr(imageData),
CGImageGetBytesPerRow(image),
NULL,
NULL,
NULL,
&pixelBuffer);
NSLog (#"CVPixelBufferCreateWithBytes returned %d", cvErr);
// calculate the time
CFAbsoluteTime thisFrameWallClockTime = CFAbsoluteTimeGetCurrent();
CFTimeInterval elapsedTime = thisFrameWallClockTime - firstFrameWallClockTime;
NSLog (#"elapsedTime: %f", elapsedTime);
CMTime presentationTime = CMTimeMake (elapsedTime * 600, 600);
// write the sample
BOOL appended = [assetWriterPixelBufferAdaptor appendPixelBuffer:pixelBuffer withPresentationTime:presentationTime];
if (appended)
{
NSLog (#"appended sample at time %lf", CMTimeGetSeconds(presentationTime));
}
else
{
NSLog (#"failed to append");
}
}
}
Then I call this method to create movie.
-(void)StartRecording
{
NSString *moviePath = [[self pathToDocumentsDirectory] stringByAppendingPathComponent:OUTPUT_FILE_NAME];
if ([[NSFileManager defaultManager] fileExistsAtPath:moviePath]) {
[[NSFileManager defaultManager] removeItemAtPath:moviePath error:nil];
}
NSURL *movieURL = [NSURL fileURLWithPath:moviePath];
NSLog(#"path=%#",movieURL);
NSError *movieError = nil;
[assetWriter release];
assetWriter = [[AVAssetWriter alloc] initWithURL:movieURL
fileType: AVFileTypeQuickTimeMovie
error: &movieError];
NSDictionary *assetWriterInputSettings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
[NSNumber numberWithInt:320], AVVideoWidthKey,
[NSNumber numberWithInt:480], AVVideoHeightKey,
nil];
assetWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType: AVMediaTypeVideo
outputSettings:assetWriterInputSettings];
assetWriterInput.expectsMediaDataInRealTime = YES;
[assetWriter addInput:assetWriterInput];
[assetWriterPixelBufferAdaptor release];
assetWriterPixelBufferAdaptor = [[AVAssetWriterInputPixelBufferAdaptor alloc]
initWithAssetWriterInput:assetWriterInput
sourcePixelBufferAttributes:nil];
[assetWriter startWriting];
firstFrameWallClockTime = CFAbsoluteTimeGetCurrent();
[assetWriter startSessionAtSourceTime: CMTimeMake(0, 1000)];
// start writing samples to it
[assetWriterTimer release];
assetWriterTimer = [NSTimer scheduledTimerWithTimeInterval:0.1
target:self
selector:#selector (writeSample:)
userInfo:nil
repeats:YES] ;
}

Answer 1

try this method....
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);
}
}