[Pycharm]Dlibの顔検出の複数人検出で困っています。

Pycharmでdlibを使って、webカメラを用いた顔検出を行なっています。（検出した顔の上に写真を貼り付けるプログラムになります。）
一人だけが顔検出されるところまではできたのですが、複数人の顔検出の仕方がわかりません。
コードは下記の通りです。どこを変えれば、複数人の顔が検出されるようになりますでしょうか？よろしくお願いします。

import cv2
import dlib
from datetime import datetime

IMAGE_PATH = "./niko.png"
CAPTURE_SCALE = 0.5

def main():

detector = dlib.get_frontal_face_detector()
predictor = dlib.shape_predictor("shape_predictor_68_face_landmarks.dat")

cap = cv2.VideoCapture(0)

while True:
    _, frame = cap.read()

    frame = img_resize(frame, CAPTURE_SCALE)
    h, w, _ = frame.shape

    img = frame
    dets = detector(frame[:, :, ::-1])

    if len(dets) > 0:
        parts = predictor(frame, dets[0]).parts()
        distance, pos = calc_distance_and_pos(img, parts)
        icon, icon_w, icon_h = load_icon(IMAGE_PATH, distance)

        if (pos != None) and (distance > 0.0):
            x = pos.x - int(icon_w / 2)
            y = pos.y - int(icon_h / 2)
            if (0 <= y) and (y <= (h - int(icon_h))) and (0 <= x) and (x <= (w - int(icon_w))):

                img = merge_images(img, icon, x, y)

    cv2.imshow("camera", img)

    k = cv2.waitKey(1) & 0xff
    if k == ord('q'):

        break
    elif k == ord('p'):

        save_image(img)
        cv2.imshow("saved", img)


cap.release()
cv2.destroyAllWindows()

def load_icon(path, distance):
icon = cv2.imread(path, -1)
icon_height, _ = icon.shape[:2]
icon = img_resize(icon, float(distance * 1.5 / icon_height))
icon_h, icon_w = icon.shape[:2]

return icon, icon_w, icon_h

def img_resize(img, scale):
h, w = img.shape[:2]
img = cv2.resize(img, (int(w * scale), int(h * scale)))
return img

def calc_distance_and_pos(img, parts):

cnt = 0
pos = None
p1 = None
distance = 0.0

for i in parts:
    if (cnt == 0):

        p1 = i
    if (cnt == 16):

        distance = ((p1.x - i.x) ** 2 + (p1.y - i.y) ** 2) ** 0.5
    if (cnt == 33):
        pos = i
    cv2.putText(img, str(cnt), (i.x, i.y), cv2.FONT_HERSHEY_SIMPLEX, 0.3, (0, 0, 255), thickness=1,
                lineType=cv2.LINE_8)
    cv2.circle(img, (i.x, i.y), 1, (255, 0, 0), -1)
    cnt = cnt + 1

return distance, pos

def save_image(img):
date = datetime.now().strftime("%Y%m%d_%H%M%S")
path = "./" + date + ".png"
cv2.imwrite(path, img)

def merge_images(bg, fg_alpha, s_x, s_y):
alpha = fg_alpha[:, :, 3]
alpha = cv2.cvtColor(alpha, cv2.COLOR_GRAY2BGR)
alpha = alpha / 255.0

fg = fg_alpha[:, :, :3]

f_h, f_w, _ = fg.shape
b_h, b_w, _ = bg.shape


print("f_w:{} f_h:{} b_w:{} b_h:{} s({}, {})".format(f_w, f_h, b_w, b_h, s_x, s_y))

bg[s_y:f_h + s_y, s_x:f_w + s_x] = (bg[s_y:f_h + s_y, s_x:f_w + s_x] * (1.0 - alpha)).astype(
    'uint8')
bg[s_y:f_h + s_y, s_x:f_w + s_x] = (bg[s_y:f_h + s_y, s_x:f_w + s_x] + (fg * alpha)).astype('uint8')

return bg

if name == 'main':
main()