create video from images and save to photo album - ios

Question

I was making a video out of an array of images and an audio file
but i can't seem to save it to the camera roll
some times it saves but some times it doesn't and gives me a strange error
outputFile.mp4 cannot be saved to the saved photos album: Error Domain=NSOSStatusErrorDomain Code=-12848 "Movie could not be played." UserInfo=0x7bd7370 {NSLocalizedDescription=Movie could not be played.}
This function creates video from array of images :
-(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];
}
This function adds the audio :
-(void)CompileFilesToMakeMovie{
AVMutableComposition* mixComposition = [AVMutableComposition composition];
NSString *documentsDirectoryPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString* audio_inputFileName = #"Rihanna-Take a Bow.mp3";
NSString* audio_inputFilePath = [NSString stringWithFormat:#"%#/%#",documentsDirectoryPath,audio_inputFileName];
NSURL* audio_inputFileUrl = [NSURL fileURLWithPath:audio_inputFilePath];
NSString* video_inputFileName = #"a.mp4";
NSString* video_inputFilePath = [NSString stringWithFormat:#"%#/%#",documentsDirectoryPath,video_inputFileName];
NSURL* video_inputFileUrl = [NSURL fileURLWithPath:video_inputFilePath];
NSString* outputFileName = #"outputFile.mp4";
NSString* outputFilePath = [NSString stringWithFormat:#"%#/%#",documentsDirectoryPath,outputFileName];
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];
//nextClipStartTime = CMTimeAdd(nextClipStartTime, a_timeRange.duration);
AVURLAsset* audioAsset = [[AVURLAsset alloc]initWithURL:audio_inputFileUrl options:nil];
CMTimeRange audio_timeRange = CMTimeRangeMake(kCMTimeZero, videoAsset.duration);
AVMutableCompositionTrack *b_compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
[b_compositionAudioTrack insertTimeRange:audio_timeRange ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:nextClipStartTime error:nil];
AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetMediumQuality];
_assetExport.outputFileType = AVFileTypeMPEG4;
_assetExport.outputURL = outputFileUrl;
[_assetExport setTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration)];
[_assetExport exportAsynchronouslyWithCompletionHandler:nil];
[audioAsset release];
[videoAsset release];
[_assetExport release];
}
The function calls :
- (void)viewDidLoad
{
[super viewDidLoad];
NSString *documentsDirectoryPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
UIImage * i = [UIImage imageNamed:#"IMG_0103.JPG"];
[self writeImagesToMovieAtPath:[NSString stringWithFormat:#"%#/%#",documentsDirectoryPath,#"a.mp4"] withSize:CGSizeMake(i.size.width, i.size.height)];
NSString* exportVideoPath1 = [NSString stringWithFormat:#"%#/%#",documentsDirectoryPath,#"a.mp4"];
NSString* exportVideoPath = [NSString stringWithFormat:#"%#/%#",documentsDirectoryPath,#"outputFile.mp4"];
UISaveVideoAtPathToSavedPhotosAlbum (exportVideoPath,self, #selector(video:didFinishSavingWithError: contextInfo:), nil);
}

Answer 1

In my case, the reason was that AVAssetWriter hasn't finished writing. Solved it with the following piece of code:
__block BOOL _finished = NO;
[assetWriter finishWritingWithCompletionHandler:^{
_finished = YES;
}];
while (!_finished) {
[NSThread sleepForTimeInterval:0.1];
}