AVAssetWriter giving bluish video file

Question

I am recoding a video from my app's screen using the AVAssetWriter class. Video records. but the recoded video is bluish one. my code to set up the AVAssetWriter is below

-(BOOL) setUpWriter {
    NSError* error = nil;
    videoWriter = [[AVAssetWriter alloc] initWithURL:[self tempFileURL] fileType:AVFileTypeAppleM4V error:&error];
    NSParameterAssert(videoWriter);

    //Configure video
    NSDictionary* videoCompressionProps = [NSDictionary dictionaryWithObjectsAndKeys:
                                           [NSNumber numberWithDouble:1024.0*1024.0], AVVideoAverageBitRateKey,
                                           nil ];

    CGSize size=[CCDirector sharedDirector].winSize;
    NSDictionary* videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                   AVVideoCodecH264, AVVideoCodecKey,
                                   [NSNumber numberWithInt:size.width], AVVideoWidthKey,
                                   [NSNumber numberWithInt: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;
}

Is there any bugs in my code. How can I solve this problem

Hi, I tried this code of yours but I am having a problem that I can't understand. My videoWriter finishes successfully but can't find the file on the outputURL. Please help me. and what does avAdaptor do? — iOS Monster, Nov 17 '12 at 07:51

score 3 · Answer 1 · answered May 26 '12 at 16:20

3

probably the problem is in incorrect pixel format, try to use kCVPixelFormatType_32BGRA

answered May 26 '12 at 16:20

BorisV

683
3
20

Rhythmic Fistman · Accepted Answer · 2012-02-15T21:05:23.780

3

Your AVAssetWriterInput is expecting ARGB but you're probably supplying it with RGBA.

That would see the probable 100% alpha interpreted as blue and the red component discarded, which would explain your bluish tint.

Hard to tell without seeing your screen recording code.

edited Feb 15 '12 at 21:05

answered Feb 15 '12 at 20:47

Rhythmic Fistman

34,352
5
87
159

Ya I think so, I'm suplying image from an openglview(of cocos2d scene) It's RGBA. Where I can change ARGB to RGBA – Johnykutty Feb 16 '12 at 03:41
I've changed 'NSDictionary* bufferAttributes=[NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:kCVPixelFormatType_32ARGB], kCVPixelBufferPixelFormatTypeKey,nil];' to 'NSDictionary* bufferAttributes=[NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:kCVPixelFormatType_32RGBA], kCVPixelBufferPixelFormatTypeKey,nil];' It crashes at 'CFDataGetBytes(image,CFRangeMake(0,CFDataGetLength(image)), destPixels);' – Johnykutty Feb 16 '12 at 04:02
It's not that simple - for RGB iOS AVFoundation prefers kCVPixelFormatType_32BGRA, so you're going to have to swap the pixel components before writing. If you're using OpenGLES2 you can use the GPU to 'swizzle' the components efficiently. More info here: http://stackoverflow.com/questions/8771471/converting-rgba-to-argb-glreadpixels-avassetwriter – Rhythmic Fistman Feb 16 '12 at 08:19
1

got solution, just converted ARGB image to RGBA image. I got the idea from purple girl http://purplelilgirl.tumblr.com/post/10974345146/mini-tutorial-how-to-capture-video-of-iphone-app-in – Johnykutty Feb 17 '12 at 04:07

AVAssetWriter giving bluish video file

2 Answers2