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To transform a CMSampleBuffer to an NSData image while ensuring that the memory does not exceed 50MB, you can use the following code:

CMSampleBufferRef sampleBuffer;
// your sample buffer

CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

CVPixelBufferLockBaseAddress(imageBuffer, 0);

uint8_t* baseAddress = (uint8_t*)CVPixelBufferGetBaseAddress(imageBuffer);
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
size_t width = CVPixelBufferGetWidth(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);
size_t bufferSize = bytesPerRow * height;

NSData *imageData;

if (bufferSize <= 50 * 1024 * 1024) { // check if buffer size exceeds 50MB
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);

    CGImageRef quartzImage = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    UIImage* image = [UIImage imageWithCGImage:quartzImage scale:1.0 orientation:UIImageOrientationRight];
    CGImageRelease(quartzImage);

    imageData = UIImageJPEGRepresentation(image, 0.8); // set compression factor to reduce memory usage
}

CVPixelBufferUnlockBaseAddress(imageBuffer,0);

return imageData;

This code creates a UIImage object from the CMSampleBuffer, then compresses it and returns an NSData object. It also includes a check to ensure that the size of the image data does not exceed 50MB.