AVAssetWriterInputPixelBufferAdaptor appendPixelBuffer - iphone

Question

I used the code below to write image to video
-(void) writeImagesToMovieAtPath:(NSString *) path withSize:(CGSize) size
{
NSLog(#"Write Started");
NSError *error = nil;
AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:
[NSURL fileURLWithPath:path] fileType:AVFileTypeMPEG4
error:&error];
NSParameterAssert(videoWriter);
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
[NSNumber numberWithInt:size.width], AVVideoWidthKey,
[NSNumber numberWithInt:size.height], AVVideoHeightKey,
nil];
AVAssetWriterInput* videoWriterInput = [[AVAssetWriterInput
assetWriterInputWithMediaType:AVMediaTypeVideo
outputSettings:videoSettings] retain];
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 = 16;
int kRecordingFPS = 30;
UIImage * im = [UIImage imageNamed:#"IMG_0103.JPG"];
NSArray * imageArray = [[NSArray alloc]initWithObjects:im,im,im,im,im,im,im,im,im,im,im,im,im,im,im,im, nil];
for(UIImage * img in imageArray)
{
buffer = [self pixelBufferFromCGImage:[img CGImage] andSize:size];
BOOL append_ok = NO;
int j = 0;
while (!append_ok && j < 30)
{
if (adaptor.assetWriterInput.readyForMoreMediaData)
{
printf("appending %d attemp %d\n", frameCount, j);
CMTime frameTime = CMTimeMake(frameCount,(int32_t) kRecordingFPS);
append_ok = [adaptor appendPixelBuffer:buffer withPresentationTime:frameTime];
if(buffer)
CVBufferRelease(buffer);
[NSThread sleepForTimeInterval:0.05];
}
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", frameCount, j);
}
frameCount++;
}
//Finish the session:
[videoWriterInput markAsFinished];
[videoWriter finishWriting];
NSLog(#"Write Ended");
[videoWriterInput release];
[videoWriter release];
[imageArray release];
}
it works at first time, but if I run code 2,3 times or more,
it reported:
！appending 0 0-0 attemp 0
！appending 0 0-0 attemp 1
My App(11385,0xb0103000) malloc: *** error for object 0x9ab4270: double free
*** set a breakpoint in malloc_error_break to debug
！appending 0 0-0 attemp 2
My App(11385,0xb0103000) malloc: *** error for object 0x9ab4270: double free
*** set a breakpoint in malloc_error_break to debug
！appending 0 0-0 attemp 3
Soemtime it caused crashing
I try to find the reason but no result,
Your comment welcome

Answer 1

Instead of using [NSThread sleepForTimeInterval:0.1];
use
while(!adaptor.assetWriterInput.readyForMoreMediaData)
{}
Because many times readyForMoreMediaData never sets to YES in 0.1 time interval.
Also try to free memory occupied by appendPixelBuffer:withPresentationTime: method
actually this method stops you from successful run

Answer 2

You need to release your buffer with CFRelease(), as it is described in The Create Rule
if ([assetWriterInput isReadyForMoreMediaData]) {
CVPixelBufferRef pixelBuffer = [self newPixelBufferFromCGImage:image.CGImage];
CMTime frameTime = CMTimeMake(frameCount,(int32_t) kRecordingFPS);
if (![adaptor appendPixelBuffer:pixelBuffer withPresentationTime:frameTime]) {
NSError *error = [videoWriter error];
NSLog(#"failed to append sbuf: %#", error);
}
CFRelease(pixelBuffer);
}