Creating `CMSampleBufferRef` from a .mov file - ios

Question

My app captures a video clip for 3 seconds, and programmatically I want to create a 15 sec clip from recorded 3 sec clip by looping it 5 times. And finally have to save 15 sec clip in CameraRoll.
I have got my 3 sec video clip via AVCaptureMovieFileOutput and I have its NSURL from delegate which is currently in NSTemporaryDirectory().
I am using AVAssetWriterInput for looping it. But it ask for CMSampleBufferRef like :
[writerInput appendSampleBuffer:sampleBuffer];
How will I gee this CMSampleBufferRef from video in NSTemporaryDirectory() ?
I have seen code for converting UIImage to CMSampleBufferRef, but I can find any for video file.
Any suggestion will be helpful. :)

Answer 1

Finally, I fixed my problem using AVMutableComposition. Here is my code :
AVMutableComposition *mixComposition = [AVMutableComposition new];
AVMutableCompositionTrack *mutableCompVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
AVURLAsset *videoAsset = [[AVURLAsset alloc]initWithURL:3SecFileURL options:nil];
CMTimeRange video_timeRange = CMTimeRangeMake(kCMTimeZero, [videoAsset duration]);
CGAffineTransform rotationTransform = CGAffineTransformMakeRotation(M_PI_2);
[mutableCompVideoTrack setPreferredTransform:rotationTransform];
CMTime currentCMTime = kCMTimeZero;
for (NSInteger count = 0 ; count < 5 ; count++)
{
[mutableCompVideoTrack insertTimeRange:video_timeRange ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:currentCMTime error:nil];
currentCMTime = CMTimeAdd(currentCMTime, [videoAsset duration]);
}
NSString *fullMoviePath = [NSTemporaryDirectory() stringByAppendingPathComponent:[#"moviefull" stringByAppendingPathExtension:#"mov"]];
NSURL *finalVideoFileURL = [NSURL fileURLWithPath:fullMoviePath];
AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetPassthrough];
[exportSession setOutputFileType:AVFileTypeQuickTimeMovie];
[exportSession setOutputURL:finalVideoFileURL];
CMTimeValue val = [mixComposition duration].value;
CMTime start = CMTimeMake(0, 1);
CMTime duration = CMTimeMake(val, 1);
CMTimeRange range = CMTimeRangeMake(start, duration);
[exportSession setTimeRange:range];
[exportSession exportAsynchronouslyWithCompletionHandler:^{
switch ([exportSession status])
{
case AVAssetExportSessionStatusFailed:
{
NSLog(#"Export failed: %# %#", [[exportSession error] localizedDescription], [[exportSession error]debugDescription]);
}
case AVAssetExportSessionStatusCancelled:
{
NSLog(#"Export canceled");
break;
}
case AVAssetExportSessionStatusCompleted:
{
NSLog(#"Export complete!");
}
default: NSLog(#"default");
}
}];

Answer 2

Take a look at AVAssetReader, this can return an CMSampleBufferRef. Keep in mind, you'll need to manipulate the timestamp for your approach to work.