makes games & other things

42 notes

Mini Tutorial: How to capture video of iPhone app in Cocos2D?

Someone asked me before if I knew how to do record the screen in Cocos2d as a video. I didn’t know how to record a video, so this guy sent me some codes, but his problem is that his code is recording the screen (taking screenshots) as a UIWindow. So my idea for him was to replace his screenshot code with AWScreenshot (by Manucorporat, search the Cocos2d forums for his code).

And here are the code bits:

#import <AVFoundation/AVFoundation.h>
#import <AVFoundation/AVAssetWriter.h>
#import <CoreVideo/CVPixelBuffer.h>
#import <CoreMedia/CMTime.h>

#import “AWScreenshot.h”

#define FRAME_WIDTH 320
#define FRAME_HEIGHT 480
#define TIME_SCALE 60 // frames per second

-(void) startScreenRecording
    NSLog(@”start screen recording”);
    // create the AVAssetWriter
    NSString *moviePath = [[self pathToDocumentsDirectory] stringByAppendingPathComponent: @”video.mov”];
    if ([[NSFileManager defaultManager] fileExistsAtPath:moviePath])
    {   [[NSFileManager defaultManager] removeItemAtPath:moviePath error:nil];
    NSURL *movieURL = [NSURL fileURLWithPath:moviePath];
    NSError *movieError = nil;
    [assetWriter release];
    assetWriter = [[AVAssetWriter alloc] initWithURL:movieURL
                                            fileType: AVFileTypeQuickTimeMovie
                                               error: &movieError];
    NSDictionary *assetWriterInputSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                              AVVideoCodecH264, AVVideoCodecKey,
                                              [NSNumber numberWithInt:FRAME_WIDTH], AVVideoWidthKey,
                                              [NSNumber numberWithInt:FRAME_HEIGHT], AVVideoHeightKey,
    assetWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType: AVMediaTypeVideo
    assetWriterInput.expectsMediaDataInRealTime = YES;
    [assetWriter addInput:assetWriterInput];
    [assetWriterPixelBufferAdaptor release];
    assetWriterPixelBufferAdaptor =  [[AVAssetWriterInputPixelBufferAdaptor  alloc]
    [assetWriter startWriting];
    firstFrameWallClockTime = CFAbsoluteTimeGetCurrent();
    [assetWriter startSessionAtSourceTime: CMTimeMake(0, TIME_SCALE)];
    // start writing samples to it
    [assetWriterTimer release];
    assetWriterTimer = [NSTimer scheduledTimerWithTimeInterval:0.1
                                                      selector:@selector (writeSample:)
                                                       repeats:YES] ;

-(void) stopScreenRecording
{   [assetWriterTimer invalidate];
    assetWriterTimer = nil;
    [assetWriter finishWriting];
    NSLog (@”finished writing”);

As you can see startScreenRecording is calls writeSample.

-(void) writeSample: (NSTimer*) _timer
{   if (assetWriterInput.readyForMoreMediaData)
        CVReturn cvErr = kCVReturnSuccess;
        // get screenshot image!
        CGImageRef image = (CGImageRef) [[self createARGBImageFromRGBAImage:[self screenshot]] CGImage];
        // prepare the pixel buffer
        CVPixelBufferRef pixelBuffer = NULL;
        CFDataRef imageData= CGDataProviderCopyData(CGImageGetDataProvider(image));
        cvErr = CVPixelBufferCreateWithBytes(kCFAllocatorDefault,
        // calculate the time
        CFAbsoluteTime thisFrameWallClockTime = CFAbsoluteTimeGetCurrent();
        CFTimeInterval elapsedTime = thisFrameWallClockTime - firstFrameWallClockTime;
        //NSLog (@”elapsedTime: %f”, elapsedTime);
        CMTime presentationTime =  CMTimeMake (elapsedTime * TIME_SCALE, TIME_SCALE);
        // 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”);
            [self stopScreenRecording];

And the code I used to take screenshot:

- (UIImage*)screenshot
{   return [AWScreenshot takeAsImage];

Notice how I called [[self createARGBImageFromRGBAImage: [self screenshot]], it’s because my UIImage is a RGBAImage, while the CVPixelBuffer’s format type is kCVPixelFormatType_32ARGB, so I had to fix thing so they match or else, my video would come up in weird tints.

I found the Googled for the createARGBImageFromRGBAImage code, and here it is:

-(UIImage *) createARGBImageFromRGBAImage: (UIImage*)image
{   CGSize dimensions = [image size];
    NSUInteger bytesPerPixel = 4;
    NSUInteger bytesPerRow = bytesPerPixel * dimensions.width;
    NSUInteger bitsPerComponent = 8;
    unsigned char *rgba = malloc(bytesPerPixel * dimensions.width * dimensions.height);
    unsigned char *argb = malloc(bytesPerPixel * dimensions.width * dimensions.height);
    CGColorSpaceRef colorSpace = NULL;
    CGContextRef context = NULL;
    colorSpace = CGColorSpaceCreateDeviceRGB();
    context = CGBitmapContextCreate(rgba, dimensions.width, dimensions.height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrderDefault); // kCGBitmapByteOrder32Big
    CGContextDrawImage(context, CGRectMake(0, 0, dimensions.width, dimensions.height), [image CGImage]);
    for (int x = 0; x < dimensions.width; x++) {
        for (int y = 0; y < dimensions.height; y++) {
            NSUInteger offset = ((dimensions.width * y) + x) * bytesPerPixel;
            argb[offset + 0] = rgba[offset + 3];
            argb[offset + 1] = rgba[offset + 0];
            argb[offset + 2] = rgba[offset + 1];
            argb[offset + 3] = rgba[offset + 2];
    colorSpace = CGColorSpaceCreateDeviceRGB();
    context = CGBitmapContextCreate(argb, dimensions.width, dimensions.height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrderDefault); // kCGBitmapByteOrder32Big
    CGImageRef imageRef = CGBitmapContextCreateImage(context);
    image = [UIImage imageWithCGImage: imageRef];
    return image;

And there we go, I managed to record the screen of my Cocos2d app and then save it as a video file.

My next problem is, how do I add audio to my video?

Filed under capture video iphone app development cocos2d tutorial video iphone app

  1. klikgames reblogged this from purplelilgirl
  2. connordenman reblogged this from purplelilgirl and added:
    This could be cool for some sort of gaming social network…
  3. purplelilgirl posted this