ASSETWriterInput for making Video from UIImages on Iphone Issues

Question

I try the following 2 methods of appending UIIMages pixelbuffer to ASSETWriterInput. Everything looks good except there's No data in the video file. What's wrong?

1)Adaptor class

AVAssetWriterInputPixelBufferAdaptor * avAdaptor = [AVAssetWriterInputPixelBufferAdaptor 
assetWriterInputPixelBufferAdaptorWithAssetWriterI nput:writerInput
sourcePixelBufferAttributes:NULL];


[avAdaptor appendPixelBufferixelBuffer withPresentationTime:CMTimeMake(1, 10)];

2)Making the

// Create sample buffer.
CMSampleBufferRef sampleBuffer = NULL;
result = CMSampleBufferCreateForImageBuffer(kCFAllocatorDef ault,
pixelBuffer, true, NULL, NULL, videoInfo, &timing, &sampleBuffer);

// Ship out the frame.
NSParameterAssert(CMSampleBufferDataIsReady(sample Buffer));
NSParameterAssert([writerInput isReadyForMoreMediaData]);
BOOL success = [writerInput appendSampleBuffer:sampleBuffer];

Answer 1

I found that for some reason I needed to append the buffer more than once. The timing in this example from a test app I made might not be proper, but since it works it should give you a good idea.

+ (void)writeImageAsMovie:(UIImage*)image toPath:(NSString*)path size:(CGSize)size duration:(int)duration 
{
    NSError *error = nil;
    AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:
                                  [NSURL fileURLWithPath:path] fileType:AVFileTypeQuickTimeMovie
                                                              error:&error];
    NSParameterAssert(videoWriter);

    NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                   AVVideoCodecH264, AVVideoCodecKey,
                                   [NSNumber numberWithInt:size.width], AVVideoWidthKey,
                                   [NSNumber numberWithInt:size.height], AVVideoHeightKey,
                                   nil];
    AVAssetWriterInput* writerInput = [[AVAssetWriterInput
                                        assetWriterInputWithMediaType:AVMediaTypeVideo
                                        outputSettings:videoSettings] retain];

    AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor
                                                     assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput
                                                     sourcePixelBufferAttributes:nil];
    NSParameterAssert(writerInput);
    NSParameterAssert([videoWriter canAddInput:writerInput]);
    [videoWriter addInput:writerInput];

    //Start a session:
    [videoWriter startWriting];
    [videoWriter startSessionAtSourceTime:kCMTimeZero];

    //Write samples:
    CVPixelBufferRef buffer = [Utils pixelBufferFromCGImage:image.CGImage size:size];
    [adaptor appendPixelBuffer:buffer withPresentationTime:kCMTimeZero];
    [adaptor appendPixelBuffer:buffer withPresentationTime:CMTimeMake(duration-1, 2)];

    //Finish the session:
    [writerInput markAsFinished];
    [videoWriter endSessionAtSourceTime:CMTimeMake(duration, 2)];
    [videoWriter finishWriting];
}