crop cmsamplebuffer cmsamplebufferref

// this ALMOST crops a CMSampleBufferRef.

//
//  SampleBufferHelper.m
//  sampleBufferBS
//
//  Created by Ivan Lesko on 2/25/16.
//  Copyright © 2016 Ivan Lesko. All rights reserved.
//

#import "SampleBufferHelper.h"

@implementation SampleBufferHelper

+ (CMSampleBufferRef)cropSampleBufferTo16by9:(CMSampleBufferRef)buffer {
  
  CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(buffer);
  CGFloat bufferWidth = CVPixelBufferGetWidth(imageBuffer);
  CGFloat bufferHeight = CVPixelBufferGetHeight(imageBuffer);
  
  CGFloat newHeight = bufferHeight * 0.75;
  CGFloat newYpos = bufferHeight * 0.875;
  
  CGRect cropRect = CGRectMake(0, 200, 2000, 1800);
  
  CIImage *ciImage = [CIImage imageWithCVPixelBuffer:imageBuffer]; //options: [NSDictionary dictionaryWithObjectsAndKeys:[NSNull null], kCIImageColorSpace, nil]];
  ciImage = [ciImage imageByCroppingToRect:cropRect];
  
  CFDictionaryRef empty; // empty value for attr value.
  CFMutableDictionaryRef attrs;
  empty = CFDictionaryCreate(kCFAllocatorDefault, // our empty IOSurface properties dictionary
                             NULL,
                             NULL,
                             0,
                             &kCFTypeDictionaryKeyCallBacks,
                             &kCFTypeDictionaryValueCallBacks);
  attrs = CFDictionaryCreateMutable(kCFAllocatorDefault,
                                    1,
                                    &kCFTypeDictionaryKeyCallBacks,
                                    &kCFTypeDictionaryValueCallBacks);
  
  CFDictionarySetValue(attrs,
                       kCVPixelBufferIOSurfacePropertiesKey,
                       empty);
  
  CVPixelBufferRef pixelBuffer;
  CVPixelBufferCreate(kCFAllocatorSystemDefault, cropRect.size.width, cropRect.size.height, kCVPixelFormatType_32BGRA, attrs, &pixelBuffer);
  
  CVPixelBufferLockBaseAddress( pixelBuffer, 0 );
  
  CIContext * ciContext = [CIContext contextWithOptions: nil];
  [ciContext render:ciImage toCVPixelBuffer:pixelBuffer];
  CVPixelBufferUnlockBaseAddress( pixelBuffer, 0 );
  
  CMSampleTimingInfo sampleTime = {
    .duration = CMSampleBufferGetDuration(buffer),
    .presentationTimeStamp = CMSampleBufferGetPresentationTimeStamp(buffer),
    .decodeTimeStamp = CMSampleBufferGetDecodeTimeStamp(buffer)
  };
  
  CMVideoFormatDescriptionRef videoInfo = NULL;
  CMVideoFormatDescriptionCreateForImageBuffer(kCFAllocatorDefault, pixelBuffer, &videoInfo);
  
  CMSampleBufferRef oBuf;
  CMSampleBufferCreateForImageBuffer(kCFAllocatorDefault, pixelBuffer, true, NULL, NULL, videoInfo, &sampleTime, &oBuf);
  
  CFRelease(attrs);
  CFRelease(empty);
  CFRelease(videoInfo);
  CFRelease(pixelBuffer);
  
  return oBuf;
}

@end