Iphone – AVFoundation – Retiming CMSampleBufferRef Video Output

avfoundationcocoacocoa-touchiphone

First time asking a question here. I'm hoping the post is clear and sample code is formatted correctly.

I'm experimenting with AVFoundation and time lapse photography.

My intent is to grab every Nth frame from the video camera of an iOS device (my iPod touch, version 4) and write each of those frames out to a file to create a timelapse. I'm using AVCaptureVideoDataOutput, AVAssetWriter and AVAssetWriterInput.

The problem is, if I use the CMSampleBufferRef passed to

captureOutput:idOutputSampleBuffer:fromConnection:

, the playback of each frame is the length of time between original input frames. A frame rate of say 1fps. I'm looking to get 30fps.

I've tried using

CMSampleBufferCreateCopyWithNewTiming()

, but then after 13 frames are written to the file, the

captureOutput:idOutputSampleBuffer:fromConnection:

stops being called. The interface is active and I can tap a button to stop the capture and save it to the photo library for playback. It appears to play back as I want it, 30fps, but it only has those 13 frames.

How can I accomplish my goal of 30fps playback?
How can I tell where the app is getting lost and why?

I've placed a flag called useNativeTime so I can test both cases. When set to YES, I get all frames I'm interested in as the callback doesn't 'get lost'. When I set that flag to NO, I only ever get 13 frames processed and am never returned to that method again. As mentioned above, in both cases I can playback the video.

Thanks for any help.

Here is where I'm trying to do the retiming.

    - (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
    BOOL useNativeTime = NO;
    BOOL appendSuccessFlag = NO;

    //NSLog(@"in captureOutpput sample buffer method");
    if( !CMSampleBufferDataIsReady(sampleBuffer) )
    {
        NSLog( @"sample buffer is not ready. Skipping sample" );
        //CMSampleBufferInvalidate(sampleBuffer);
        return;
    }

    if (! [inputWriterBuffer isReadyForMoreMediaData])
    {
        NSLog(@"Not ready for data.");
    }
    else {
        // Write every first frame of n frames (30 native from camera). 
        intervalFrames++;
        if (intervalFrames > 30) {
            intervalFrames = 1;
        }
        else if (intervalFrames != 1) {
            //CMSampleBufferInvalidate(sampleBuffer);
            return;
        }

        // Need to initialize start session time.
        if (writtenFrames < 1) {
            if (useNativeTime) imageSourceTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
            else imageSourceTime = CMTimeMake( 0 * 20 ,600); //CMTimeMake(1,30);
            [outputWriter startSessionAtSourceTime: imageSourceTime];
            NSLog(@"Starting CMtime");
            CMTimeShow(imageSourceTime);
        }

        if (useNativeTime) {
            imageSourceTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
            CMTimeShow(imageSourceTime);
            // CMTime myTiming = CMTimeMake(writtenFrames * 20,600);
            // CMSampleBufferSetOutputPresentationTimeStamp(sampleBuffer, myTiming); // Tried but has no affect.
            appendSuccessFlag = [inputWriterBuffer appendSampleBuffer:sampleBuffer];
        }
        else {
            CMSampleBufferRef newSampleBuffer;
            CMSampleTimingInfo sampleTimingInfo;
            sampleTimingInfo.duration = CMTimeMake(20,600);
            sampleTimingInfo.presentationTimeStamp = CMTimeMake( (writtenFrames + 0) * 20,600);
            sampleTimingInfo.decodeTimeStamp = kCMTimeInvalid;
            OSStatus myStatus;

            //NSLog(@"numSamples of sampleBuffer: %i", CMSampleBufferGetNumSamples(sampleBuffer) );
            myStatus = CMSampleBufferCreateCopyWithNewTiming(kCFAllocatorDefault,
                                                             sampleBuffer,
                                                             1,
                                                             &sampleTimingInfo, // maybe a little confused on this param.
                                                             &newSampleBuffer);
            // These confirm the good heath of our newSampleBuffer.
            if (myStatus != 0) NSLog(@"CMSampleBufferCreateCopyWithNewTiming() myStatus: %i",myStatus);
            if (! CMSampleBufferIsValid(newSampleBuffer)) NSLog(@"CMSampleBufferIsValid NOT!");

            // No affect.
            //myStatus = CMSampleBufferMakeDataReady(newSampleBuffer);  // How is this different; CMSampleBufferSetDataReady ?
            //if (myStatus != 0) NSLog(@"CMSampleBufferMakeDataReady() myStatus: %i",myStatus);

            imageSourceTime = CMSampleBufferGetPresentationTimeStamp(newSampleBuffer);
            CMTimeShow(imageSourceTime);
            appendSuccessFlag = [inputWriterBuffer appendSampleBuffer:newSampleBuffer];
            //CMSampleBufferInvalidate(sampleBuffer); // Docs don't describe action. WTF does it do? Doesn't seem to affect my problem. Used with CMSampleBufferSetInvalidateCallback maybe?
            //CFRelease(sampleBuffer); // - Not surprisingly - “EXC_BAD_ACCESS”
        }

        if (!appendSuccessFlag)
        {
            NSLog(@"Failed to append pixel buffer");
        }
        else {
            writtenFrames++;
            NSLog(@"writtenFrames: %i", writtenFrames);
            }
    }

    //[self displayOuptutWritterStatus];    // Expect and see AVAssetWriterStatusWriting.
}

My setup routine.

    - (IBAction) recordingStartStop: (id) sender
{
    NSError * error;

    if (self.isRecording) {
        NSLog(@"~~~~~~~~~ STOPPING RECORDING ~~~~~~~~~");
        self.isRecording = NO;
        [recordingStarStop setTitle: @"Record" forState: UIControlStateNormal];

        //[self.captureSession stopRunning];
        [inputWriterBuffer markAsFinished];
        [outputWriter endSessionAtSourceTime:imageSourceTime];
        [outputWriter finishWriting]; // Blocks until file is completely written, or an error occurs.
        NSLog(@"finished CMtime");
        CMTimeShow(imageSourceTime);

        // Really, I should loop through the outputs and close all of them or target specific ones.
        // Since I'm only recording video right now, I feel safe doing this.
        [self.captureSession removeOutput: [[self.captureSession outputs] objectAtIndex: 0]];

        [videoOutput release];
        [inputWriterBuffer release];
        [outputWriter release];
        videoOutput = nil;
        inputWriterBuffer = nil;
        outputWriter = nil;
        NSLog(@"~~~~~~~~~ STOPPED RECORDING ~~~~~~~~~");
        NSLog(@"Calling UIVideoAtPathIsCompatibleWithSavedPhotosAlbum.");
        NSLog(@"filePath: %@", [projectPaths movieFilePath]);
        if (UIVideoAtPathIsCompatibleWithSavedPhotosAlbum([projectPaths movieFilePath])) {
            NSLog(@"Calling UISaveVideoAtPathToSavedPhotosAlbum.");
            UISaveVideoAtPathToSavedPhotosAlbum ([projectPaths movieFilePath], self, @selector(video:didFinishSavingWithError: contextInfo:), nil);
        }
        NSLog(@"~~~~~~~~~ WROTE RECORDING to PhotosAlbum ~~~~~~~~~");
    }
    else {
        NSLog(@"~~~~~~~~~ STARTING RECORDING ~~~~~~~~~");
        projectPaths = [[ProjectPaths alloc] initWithProjectFolder: @"TestProject"];
        intervalFrames = 30;

        videoOutput = [[AVCaptureVideoDataOutput alloc] init];
        NSMutableDictionary * cameraVideoSettings = [[[NSMutableDictionary alloc] init] autorelease];
        NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey;
        NSNumber* value = [NSNumber numberWithUnsignedInt: kCVPixelFormatType_32BGRA]; //kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange];
        [cameraVideoSettings setValue: value forKey: key];
        [videoOutput setVideoSettings: cameraVideoSettings];
        [videoOutput setMinFrameDuration: CMTimeMake(20, 600)]; //CMTimeMake(1, 30)]; // 30fps
        [videoOutput setAlwaysDiscardsLateVideoFrames: YES];

        queue = dispatch_queue_create("cameraQueue", NULL);
        [videoOutput setSampleBufferDelegate: self queue: queue];
        dispatch_release(queue);

        NSMutableDictionary *outputSettings = [[[NSMutableDictionary alloc] init] autorelease];
        [outputSettings setValue: AVVideoCodecH264 forKey: AVVideoCodecKey];
        [outputSettings setValue: [NSNumber numberWithInt: 1280] forKey: AVVideoWidthKey]; // currently assuming
        [outputSettings setValue: [NSNumber numberWithInt: 720] forKey: AVVideoHeightKey];

        NSMutableDictionary *compressionSettings = [[[NSMutableDictionary alloc] init] autorelease];
        [compressionSettings setValue: AVVideoProfileLevelH264Main30 forKey: AVVideoProfileLevelKey];
        //[compressionSettings setValue: [NSNumber numberWithDouble:1024.0*1024.0] forKey: AVVideoAverageBitRateKey];
        [outputSettings setValue: compressionSettings forKey: AVVideoCompressionPropertiesKey];

        inputWriterBuffer = [AVAssetWriterInput assetWriterInputWithMediaType: AVMediaTypeVideo outputSettings: outputSettings];
        [inputWriterBuffer retain];
        inputWriterBuffer.expectsMediaDataInRealTime = YES;

        outputWriter = [AVAssetWriter assetWriterWithURL: [projectPaths movieURLPath] fileType: AVFileTypeQuickTimeMovie error: &error];
        [outputWriter retain];

        if (error) NSLog(@"error for outputWriter = [AVAssetWriter assetWriterWithURL:fileType:error:");
        if ([outputWriter canAddInput: inputWriterBuffer]) [outputWriter addInput: inputWriterBuffer];
        else NSLog(@"can not add input");

        if (![outputWriter canApplyOutputSettings: outputSettings forMediaType:AVMediaTypeVideo]) NSLog(@"ouptutSettings are NOT supported");

        if ([captureSession canAddOutput: videoOutput]) [self.captureSession addOutput: videoOutput];
        else NSLog(@"could not addOutput: videoOutput to captureSession");

        //[self.captureSession startRunning];
        self.isRecording = YES;
        [recordingStarStop setTitle: @"Stop" forState: UIControlStateNormal];

        writtenFrames = 0;
        imageSourceTime = kCMTimeZero;
        [outputWriter startWriting];
        //[outputWriter startSessionAtSourceTime: imageSourceTime];
        NSLog(@"~~~~~~~~~ STARTED RECORDING ~~~~~~~~~");
        NSLog (@"recording to fileURL: %@", [projectPaths movieURLPath]);
    }

    NSLog(@"isRecording: %@", self.isRecording ? @"YES" : @"NO");

    [self displayOuptutWritterStatus];  
}

Best Answer

OK, I found the bug in my first post.

When using

myStatus = CMSampleBufferCreateCopyWithNewTiming(kCFAllocatorDefault,
                                                 sampleBuffer,
                                                 1,
                                                 &sampleTimingInfo, 
                                                 &newSampleBuffer);

you need to balance that with a CFRelease(newSampleBuffer);

The same idea holds true when using a CVPixelBufferRef with a piexBufferPool of an AVAssetWriterInputPixelBufferAdaptor instance. You would use CVPixelBufferRelease(yourCVPixelBufferRef); after calling the appendPixelBuffer: withPresentationTime: method.

Hope this is helpful to someone else.

Related Solutions

Ios – AVFoundation, how to turn off the shutter sound when captureStillImageAsynchronouslyFromConnection

I used this code once to capture iOS default shutter sound (here is list of sound file names https://github.com/TUNER88/iOSSystemSoundsLibrary):

NSString *path = @"/System/Library/Audio/UISounds/photoShutter.caf";
NSString *docs = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSData *data = [NSData dataWithContentsOfFile:path];
[data writeToFile:[docs stringByAppendingPathComponent:@"photoShutter.caf"] atomically:YES];

Then I used third-party app to extract photoShutter.caf from Documents directory (DiskAid for Mac). Next step I opened photoShutter.caf in Audacity audio editor and applied inversion effect, it looks like this on high zoom:

enter image description here

Then I saved this sound as photoShutter2.caf and tried to play this sound right before captureStillImageAsynchronouslyFromConnection:

static SystemSoundID soundID = 0;
if (soundID == 0) {
    NSString *path = [[NSBundle mainBundle] pathForResource:@"photoShutter2" ofType:@"caf"];
    NSURL *filePath = [NSURL fileURLWithPath:path isDirectory:NO];
    AudioServicesCreateSystemSoundID((__bridge CFURLRef)filePath, &soundID);
}
AudioServicesPlaySystemSound(soundID);

[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:
...

And this really works! I runs test several times, every time I hear no shutter sound :)

You can get already inverted sound, captured on iPhone 5S iOS 7.1.1 from this link: https://www.dropbox.com/s/1echsi6ivbb85bv/photoShutter2.caf

Create video from array of UIImages and save the video to iPhone library. AVAssetLibrary +AVFoundation

-(void)convertimagetoVideo
{
    ///////////// setup OR function def if we move this to a separate function ////////////
    // this should be moved to its own function, that can take an imageArray, videoOutputPath, etc...


NSError *error = nil;


// set up file manager, and file videoOutputPath, remove "test_output.mp4" if it exists...
//NSString *videoOutputPath = @"/Users/someuser/Desktop/test_output.mp4";
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(400, 200);
//    NSUInteger fps = 30;
    NSUInteger fps = 30;

//NSMutableArray *imageArray;
//imageArray = [[NSMutableArray alloc] initWithObjects:@"download.jpeg", @"download2.jpeg", nil];
NSMutableArray *imageArray;
NSArray* imagePaths = [[NSBundle mainBundle] pathsForResourcesOfType:@"png" inDirectory:nil];
imageArray = [[NSMutableArray alloc] initWithCapacity:imagePaths.count];
NSLog(@"-->imageArray.count= %i", imageArray.count);
for (NSString* path in imagePaths)
{
    [imageArray addObject:[UIImage imageWithContentsOfFile:path]];
    //NSLog(@"-->image path= %@", path);
}

//////////////     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:imageSize.width], 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 imageArray)
{
    //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,%d)",frameCount,[imageArray count]);

            //CMTime frameTime = CMTimeMake((int64_t), (int32_t)2);

            CMTime frameTime = CMTimeMake(frameCount*frameDuration,(int32_t) fps);
            NSLog(@"seconds = %f, %u, %d", CMTimeGetSeconds(frameTime),fps,j);
            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 finishWriting];
NSLog(@"Write Ended");

}


-(void)CompileFilestomakeVideo
{

    // set up file manager, and file videoOutputPath, remove "test_output.mp4" if it exists...
    //NSString *videoOutputPath = @"/Users/someuser/Desktop/test_output.mp4";
    NSString *documentsDirectory = [NSHomeDirectory()
                                    stringByAppendingPathComponent:@"Documents"];
    NSString *videoOutputPath = [documentsDirectory stringByAppendingPathComponent:@"test_output.mp4"];
    //NSLog(@"-->videoOutputPath= %@", videoOutputPath);
    // get rid of existing mp4 if exists...

    AVMutableComposition* mixComposition = [AVMutableComposition composition];

    NSString *bundleDirectory = [[NSBundle mainBundle] bundlePath];
    // audio input file...
    NSString *audio_inputFilePath = [bundleDirectory stringByAppendingPathComponent:@"30secs.mp3"];
    NSURL    *audio_inputFileUrl = [NSURL fileURLWithPath:audio_inputFilePath];

    // 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];

    //nextClipStartTime = CMTimeAdd(nextClipStartTime, a_timeRange.duration);

    AVURLAsset* audioAsset = [[AVURLAsset alloc]initWithURL:audio_inputFileUrl options:nil];
    CMTimeRange audio_timeRange = CMTimeRangeMake(kCMTimeZero, audioAsset.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:AVAssetExportPresetHighestQuality];
    _assetExport.outputFileType = @"com.apple.quicktime-movie";
    //_assetExport.outputFileType = @"public.mpeg-4";
    //NSLog(@"support file types= %@", [_assetExport supportedFileTypes]);
    _assetExport.outputURL = outputFileUrl;

    [_assetExport exportAsynchronouslyWithCompletionHandler:
     ^(void ) {
         [self saveVideoToAlbum:outputFilePath];
     }
     ];

    ///// THAT IS IT DONE... the final video file will be written here...
    NSLog(@"DONE.....outputFilePath--->%@", outputFilePath);

    // the final video file will be located somewhere like here:
    // /Users/caferrara/Library/Application Support/iPhone Simulator/6.0/Applications/D4B12FEE-E09C-4B12-B772-7F1BD6011BE1/Documents/outputFile.mov


    ////////////////////////////////////////////////////////////////////////////
    ////////////////////////////////////////////////////////////////////////////
}
- (void) saveVideoToAlbum:(NSString*)path {

    NSLog(@"saveVideoToAlbum");

    if(UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(path)){
        UISaveVideoAtPathToSavedPhotosAlbum (path, self, @selector(video:didFinishSavingWithError: contextInfo:), nil);
    }
}

-(void) video:(NSString *)videoPath didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo {
    if(error)
        NSLog(@"error: %@", error);
    else
        NSLog(@" OK");
}



////////////////////////
- (CVPixelBufferRef) pixelBufferFromCGImage: (CGImageRef) image {

    CGSize size = CGSizeMake(400, 200);

    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,
                                                 kCGImageAlphaPremultipliedFirst);
    //kCGImageAlphaNoneSkipFirst);
    CGContextConcatCTM(context, CGAffineTransformMakeRotation(0));
    CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image),
                                           CGImageGetHeight(image)), image);
    CGColorSpaceRelease(rgbColorSpace);
    CGContextRelease(context);

    CVPixelBufferUnlockBaseAddress(pxbuffer, 0);

    return pxbuffer;
}

Best Answer

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Ios – AVFoundation, how to turn off the shutter sound when captureStillImageAsynchronouslyFromConnection

Create video from array of UIImages and save the video to iPhone library. AVAssetLibrary +AVFoundation

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