Converting array of images to mp4 - ios

Question

I tried to convert an array of images to one mp4 file and it seems to work but when the video player starts to play it only shows a black view. I followed some other posts on here to convert images and this what I got. When I test it, all the pictures are converted and the video gets created. But when the video plays, it only shows a black view. Any help or clarification will be appreciated.
- (void) createVideoPlayer:(NSArray *)imagesArray
{
NSError *error = nil;
NSFileManager *fileMgr = [NSFileManager defaultManager];
NSString *documentsDirectory = [NSHomeDirectory() stringByAppendingPathComponent:#"Documents"];
NSString *videoOutputPath = [documentsDirectory stringByAppendingPathComponent:#"test_output.mp4"];
//NSLog(#"-->videoOutputPath= %#", videoOutputPath);
// get rid of existing mp4 if exists...
if ([fileMgr removeItemAtPath:videoOutputPath error:&error] != YES)
NSLog(#"Unable to delete file: %#", [error localizedDescription]);
CGSize imageSize = CGSizeMake(213, 320);
NSUInteger fps = 3;
////////////// end setup ///////////////////////////////////
NSLog(#"Start building video from defined frames.");
AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:
[NSURL fileURLWithPath:videoOutputPath] fileType:AVFileTypeQuickTimeMovie
error:&error];
NSParameterAssert(videoWriter);
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
[NSNumber numberWithInt:320], AVVideoWidthKey,
[NSNumber numberWithInt:imageSize.height], AVVideoHeightKey,
nil];
AVAssetWriterInput* videoWriterInput = [AVAssetWriterInput
assetWriterInputWithMediaType:AVMediaTypeVideo
outputSettings:videoSettings];
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 = 0;
double numberOfSecondsPerFrame = 6;
double frameDuration = fps * numberOfSecondsPerFrame;
//for(VideoFrame * frm in imageArray)
NSLog(#"**************************************************");
for(UIImage * img in imagesArray)
{
//UIImage * img = frm._imageFrame;
buffer = [self pixelBufferFromCGImage:[img CGImage]];
BOOL append_ok = NO;
int j = 0;
while (!append_ok && j < 30)
{
if (adaptor.assetWriterInput.readyForMoreMediaData)
{
//print out status:
NSLog(#"Processing video frame (%d,%lu)",frameCount,(unsigned long)[imagesArray count]);
CMTime frameTime = CMTimeMake(frameCount*frameDuration,(int32_t) fps);
append_ok = [adaptor appendPixelBuffer:buffer withPresentationTime:frameTime];
if(!append_ok)
{
NSError *error = videoWriter.error;
if(error!=nil)
NSLog(#"Unresolved error %#,%#.", error, [error userInfo]);
}
}
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, with error.", frameCount, j);
frameCount++;
}
NSLog(#"**************************************************");
//Finish the session:
[videoWriterInput markAsFinished];
[videoWriter finishWritingWithCompletionHandler:^{
}];
NSLog(#"Write Ended");
AVMutableComposition* mixComposition = [AVMutableComposition composition];
// this is the video file that was just written above, full path to file is in --> videoOutputPath
NSURL *video_inputFileUrl = [NSURL fileURLWithPath:videoOutputPath];
// create the final video output file as MOV file - may need to be MP4, but this works so far...
NSString *outputFilePath = [documentsDirectory stringByAppendingPathComponent:#"final_video.mp4"];
NSURL *outputFileUrl = [NSURL fileURLWithPath:outputFilePath];
if ([[NSFileManager defaultManager] fileExistsAtPath:outputFilePath])
[[NSFileManager defaultManager] removeItemAtPath:outputFilePath error:nil];
CMTime nextClipStartTime = kCMTimeZero;
AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:video_inputFileUrl options:nil];
CMTimeRange video_timeRange = CMTimeRangeMake(kCMTimeZero,videoAsset.duration);
AVMutableCompositionTrack *a_compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[a_compositionVideoTrack insertTimeRange:video_timeRange ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:nextClipStartTime error:nil];
AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality];
_assetExport.outputFileType = #"public.mpeg-4";
//NSLog(#"support file types= %#", [_assetExport supportedFileTypes]);
_assetExport.outputURL = outputFileUrl;
[_assetExport exportAsynchronouslyWithCompletionHandler: ^(void ) {
// [self SaveVideo:outputFilePath];
moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:[NSURL fileURLWithPath:outputFilePath]];
[moviePlayer.view setFrame:CGRectMake(0, 100, 320, 320)];
[moviePlayer prepareToPlay];
// And other options you can look through the documentation.
[self.view addSubview:moviePlayer.view];
[moviePlayer play];
}];
NSLog(#"DONE.....outputFilePath--->%#", outputFilePath);
}
- (CVPixelBufferRef) pixelBufferFromCGImage: (CGImageRef) image {
CGSize size = CGSizeMake(300, 300);
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey,
[NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey,
nil];
CVPixelBufferRef pxbuffer = NULL;
CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault,
size.width,
size.height,
kCVPixelFormatType_32ARGB,
(__bridge CFDictionaryRef) options,
&pxbuffer);
if (status != kCVReturnSuccess){
NSLog(#"Failed to create pixel buffer");
}
CVPixelBufferLockBaseAddress(pxbuffer, 0);
void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(pxdata, size.width,
size.height, 8, 4*size.width, rgbColorSpace,
kCGImageAlphaPremultipliedLast);
CGContextConcatCTM(context, CGAffineTransformMakeRotation(0));
CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image),
CGImageGetHeight(image)), image);
CGColorSpaceRelease(rgbColorSpace);
CGContextRelease(context);
CVPixelBufferUnlockBaseAddress(pxbuffer, 0);
return pxbuffer;
}

Answer 1

All UI updates must be on the main thread, double check the completionHandler is executing on main thread by calling:
NSLog(#"%d", [NSThread isMainThread]);
To execute on the mainthread use GCD:
dispatch_async(dispatch_get_main_queue(), ^{
// your UI update
});
Also you should always create a weak reference when capturing Self to avoid strong reference cycle by creating a local instance:
__weak typeof(self) weakSelf = self; // now use weakSelf.doSomething