How to use CVPixelBufferPool in conjunction with AVAssetWriterInputPixelBufferAdaptor in iphone?

Question

Hi Everybody,

I have successfully created video from images using the following code

-(void)writeImageAsMovie:(NSArray *)array 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];

CVPixelBufferRef buffer = NULL;
buffer = [self pixelBufferFromCGImage:[[array objectAtIndex:0] CGImage]];
[adaptor appendPixelBuffer:buffer withPresentationTime:kCMTimeZero];

//Write samples:
for (int i = 0;i<[array count]; i++)
{
    if([writerInput isReadyForMoreMediaData])
    {
        NSLog(@"inside for loop %d",i);
        CMTime frameTime = CMTimeMake(1, 20);

        CMTime lastTime=CMTimeMake(i, 20); //i is from 0 to 24 of the loop above

        CMTime presentTime=CMTimeAdd(lastTime, frameTime);

        buffer = [self pixelBufferFromCGImage:[[array objectAtIndex:i] CGImage]];

        [adaptor appendPixelBuffer:buffer withPresentationTime:presentTime];

    }
    else
    {
        NSLog(@"error");
        i--;
    }
}
NSLog(@"outside for loop");

//Finish the session:
[writerInput markAsFinished];
[videoWriter finishWriting];
}

Here i have used CVPixelBufferRef Instead of this i want to use the CVPixelBufferPoolRef in conjunction with AVAssetWriterInputPixelBufferAdaptor

Can anybody help me with a sample code which i can debug and use...

Plz help me with this...

Thanx in advance...

Answer 1

You are passing nil 'sourcePixelBufferAttributes', because of which the pixel buffer pool will not get created:

AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor
                                             assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput
                                             sourcePixelBufferAttributes:nil];

Instead pass some attributes, eg:

NSDictionary *bufferAttributes = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:kCVPixelFormatType_32ARGB], kCVPixelBufferPixelFormatTypeKey, nil];

Then you can use the pool to create the pixel buffers, like:

CVPixelBufferPoolCreatePixelBuffer (NULL, adaptor.pixelBufferPool, &pixelBuffer);