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POConverting images to Videos iOS5
 

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  1. POConverting images to Videos iOS5
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    <p>I am writing an app that draws on screen and then converts a series of screen grabbed images to videos. However the final video appear a bit off (appears to have rotated).</p> <p>Basically my captured video should draw something like this: <img src="https://i.imgur.com/h56Lc.png" alt="In Simulator:--&gt;"></p> <hr> <p>However it appears to be something like this in the final video: <img src="https://i.imgur.com/TSu6A.png" alt="recorded video:--&gt;"></p> <p>My code is shown below. I'm guessing the problem is in the PixelBuffer logic &amp; that I need to apply some type of a transform. Any suggestions?</p> <pre><code>- (void)exportImages:(NSMutableArray *)imageArray asVideoToPath:(NSString *)path withFrameSize:(CGSize)imageSize framesPerSecond:(NSUInteger)fps { NSFileManager *fileManager = [[NSFileManager alloc] init]; if([fileManager fileExistsAtPath:path]) [fileManager removeItemAtPath:path error:NULL]; NSLog(@"Start building video from defined frames."); NSError *error = nil; AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL: [NSURL fileURLWithPath:path] fileType:AVFileTypeQuickTimeMovie error:&amp;error]; NSParameterAssert(videoWriter); NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys: AVVideoCodecH264, AVVideoCodecKey, [NSNumber numberWithInt:imageSize.width], AVVideoWidthKey, [NSNumber numberWithInt:imageSize.height], AVVideoHeightKey, nil]; AVAssetWriterInput* videoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings]; AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:videoWriterInput sourcePixelBufferAttributes:nil]; NSParameterAssert(videoWriterInput); NSParameterAssert([videoWriter canAddInput:videoWriterInput]); videoWriterInput.expectsMediaDataInRealTime = YES; [videoWriter addInput:videoWriterInput]; //Start a session: [videoWriter startWriting]; [videoWriter startSessionAtSourceTime:kCMTimeZero]; CVPixelBufferRef buffer = NULL; //convert uiimage to CGImage. int frameCount = 0; for(VideoFrame * frm in imageArray) { UIImage * img = frm._imageFrame; buffer = [self pixelBufferFromCGImage:[img CGImage]]; BOOL append_ok = NO; int j = 0; while (!append_ok &amp;&amp; j &lt; 30) { if (adaptor.assetWriterInput.readyForMoreMediaData) { //print out status:: NSString *border = @"**************************************************"; NSLog(@"\n%@\nProcessing video frame (%d,%d).\n%@",border,frameCount,[imageArray count],border); CMTime frameTime = CMTimeMake(frameCount,(int32_t) fps); append_ok = [adaptor appendPixelBuffer:buffer withPresentationTime:frameTime]; if(!append_ok){ NSError *error = videoWriter.error; if(error!=nil) { NSLog(@"Unresolved error %@,%@.", error, [error userInfo]); } } } else { printf("adaptor not ready %d, %d\n", frameCount, j); [NSThread sleepForTimeInterval:0.1]; } j++; } if (!append_ok) { printf("error appending image %d times %d\n, with error.", frameCount, j); } frameCount++; } //Finish the session: [videoWriterInput markAsFinished]; [videoWriter finishWriting]; NSLog(@"Write Ended"); </code></pre> <p>}</p> <pre><code>- (CVPixelBufferRef) pixelBufferFromCGImage: (CGImageRef) image { NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey, [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey, nil]; CVPixelBufferRef pxbuffer = NULL; CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, self.frame.size.width, self.frame.size.height, kCVPixelFormatType_32ARGB, (__bridge CFDictionaryRef) options, &amp;pxbuffer); if (status != kCVReturnSuccess){ NSLog(@"Failed to create pixel buffer"); } CVPixelBufferLockBaseAddress(pxbuffer, 0); void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer); CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB(); CGContextRef context = CGBitmapContextCreate(pxdata, self.frame.size.width, self.frame.size.height, 8, 4*self.frame.size.width, rgbColorSpace, kCGImageAlphaPremultipliedFirst); //kCGImageAlphaNoneSkipFirst); CGContextConcatCTM(context, CGAffineTransformMakeRotation(0)); CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image), CGImageGetHeight(image)), image); CGColorSpaceRelease(rgbColorSpace); CGContextRelease(context); CVPixelBufferUnlockBaseAddress(pxbuffer, 0); return pxbuffer; </code></pre> <p>}</p> <p>FYI: I also tried to save the screen grabbed images to a png file and checked them -- they were all correct. </p>
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    1. USAnil
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    1. COThere may be divisibility requirements for the width of your video. What's self.frame.size.height? PS concatting CGAffineTransformMakeRotation(0) does nothing.
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      1. POConverting images to Videos iOS5
      1. USRhythmic Fistman
    2. COit is (286,400). Can you explain a bit more what you mean by divisibility requirements?
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      1. POConverting images to Videos iOS5
      1. USAnil
    3. COIt may need to be divisible by 4 (or something!), but I'm not sure.
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      1. POConverting images to Videos iOS5
      1. USRhythmic Fistman
 

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