method of creating positive images

Hi there, I am creating traincascade file for detecting the bird tail, after reading opencv manual, I created positive and negative images as below. - I generate about 4500 negative images from a video, all images have the same size ~ 1080x1920, then I converted them into 680x480 size by using image size converter. - I cropped the positive object manually, and I have got 1052 images that have the size 230x433, 133x522, 233x355... those sizes are quite different, then I use a converting image size to make all positive images size to be 92x112 after that I created positives.txt, negagives.txt files and vector file, then run opencv_traincascade to make training file, by now, it have taken 4 days but the traincascade is in stage 3. Am I wrong on creating positive and negative images? is it Ok to use an image converter for image size like ALSee? Any feedback? Thank you in advance. Tim.