diff --git a/perturbation/check_video.py b/perturbation/check_video.py
index f5da18a..54e923a 100644
--- a/perturbation/check_video.py
+++ b/perturbation/check_video.py
@@ -1,23 +1,12 @@
 import argparse
 import os
-
 import cv2
 
-
 def parse_args():
     parser = argparse.ArgumentParser(description='Check video information.')
-    parser.add_argument('--vid_in',
-                        type=str,
-                        required=True,
-                        help='path to the input video')
-    parser.add_argument('--vid_out',
-                        type=str,
-                        required=True,
-                        help='path to the output video')
-    args = parser.parse_args()
-
-    return args
-
+    parser.add_argument('--vid_in', type=str, required=True, help='Path to the input video')
+    parser.add_argument('--vid_out', type=str, required=True, help='Path to the output video')
+    return parser.parse_args()
 
 def get_vid_info(vid):
     w = vid.get(cv2.CAP_PROP_FRAME_WIDTH)
@@ -25,44 +14,51 @@ def get_vid_info(vid):
     fps = vid.get(cv2.CAP_PROP_FPS)
     fourcc = vid.get(cv2.CAP_PROP_FOURCC)
     frame_count = vid.get(cv2.CAP_PROP_FRAME_COUNT)
-
     return w, h, fps, fourcc, frame_count
 
-
 def main():
     args = parse_args()
-
     vid_in = args.vid_in
     vid_out = args.vid_out
 
-    # check input args
-    assert os.path.exists(vid_in), 'Input video does not exist.'
-    assert os.path.exists(vid_out), 'Output video does not exist.'
+    if not os.path.exists(vid_in):
+        raise FileNotFoundError('Input video does not exist.')
+    
+    if not os.path.exists(vid_out):
+        raise FileNotFoundError('Output video does not exist.')
 
-    # check video info
-    vid1 = cv2.VideoCapture(vid_in)
-    w1, h1, fps1, fourcc1, frame_count1 = get_vid_info(vid1)
-    vid1.release()
-    vid2 = cv2.VideoCapture(vid_out)
-    w2, h2, fps2, fourcc2, frame_count2 = get_vid_info(vid2)
-    vid2.release()
-    assert w1 == w2, ('Frame width should be the same, '
-                      f'but got {w1} in input video, {w2} in output video.')
-    assert h1 == h2, ('Frame height should be the same, '
-                      f'but got {h1} in input video, {h2} in output video.')
-    assert fps1 == fps2, ('Video fps should be the same, but got '
-                          f'{fps1} in input video, {fps2} in output video.')
-    assert fourcc1 == fourcc2, ('Video fourcc should be the same, but got '
-                                f'{fourcc1} in input video, {fourcc2} in '
-                                'output video.')
-    assert frame_count1 == frame_count2, ('Frame count should be the same, '
-                                          f'but got {frame_count1} in '
-                                          f'input video, {frame_count2} in '
-                                          'output video.')
+    try:
+        vid1 = cv2.VideoCapture(vid_in)
+        if not vid1.isOpened():
+            raise RuntimeError('Could not open input video.')
 
-    # pass all assertions, succeed
-    print('No problem.')
+        w1, h1, fps1, fourcc1, frame_count1 = get_vid_info(vid1)
+        vid1.release()
+
+        vid2 = cv2.VideoCapture(vid_out)
+        if not vid2.isOpened():
+            raise RuntimeError('Could not open output video.')
+
+        w2, h2, fps2, fourcc2, frame_count2 = get_vid_info(vid2)
+        vid2.release()
 
+    except Exception as e:
+        print(f"Error occurred: {e}")
+        return
+
+    # Check video properties
+    if w1 != w2:
+        raise ValueError(f'Frame width mismatch: {w1} in input vs {w2} in output.')
+    if h1 != h2:
+        raise ValueError(f'Frame height mismatch: {h1} in input vs {h2} in output.')
+    if fps1 != fps2:
+        raise ValueError(f'FPS mismatch: {fps1} in input vs {fps2} in output.')
+    if fourcc1 != fourcc2:
+        raise ValueError(f'FOURCC mismatch: {fourcc1} in input vs {fourcc2} in output.')
+    if frame_count1 != frame_count2:
+        raise ValueError(f'Frame count mismatch: {frame_count1} in input vs {frame_count2} in output.')
+
+    print('No problem.')
 
 if __name__ == '__main__':
     main()
diff --git a/perturbation/distortions.py b/perturbation/distortions.py
index 4a7faaf..458e4b5 100644
--- a/perturbation/distortions.py
+++ b/perturbation/distortions.py
@@ -1,92 +1,168 @@
 import math
 import os
 import random
-
 import cv2
 import numpy as np
 
-
 def bgr2ycbcr(img_bgr):
+    """
+    Convert BGR image to YCbCr color space.
+
+    Args:
+        img_bgr (np.ndarray): Input image in BGR format.
+
+    Returns:
+        np.ndarray: Image converted to YCbCr format.
+    """
     img_bgr = img_bgr.astype(np.float32)
     img_ycrcb = cv2.cvtColor(img_bgr, cv2.COLOR_BGR2YCR_CB)
-    img_ycbcr = img_ycrcb[:, :, (0, 2, 1)].astype(np.float32)
-    # to [16/255, 235/255]
+    img_ycbcr = img_ycrcb[:, :, (0, 2, 1)]
+    
+    # Scale to [16/255, 235/255] for Y and [16/255, 240/255] for Cb and Cr
     img_ycbcr[:, :, 0] = (img_ycbcr[:, :, 0] * (235 - 16) + 16) / 255.0
-    # to [16/255, 240/255]
     img_ycbcr[:, :, 1:] = (img_ycbcr[:, :, 1:] * (240 - 16) + 16) / 255.0
-
+    
     return img_ycbcr
 
-
 def ycbcr2bgr(img_ycbcr):
+    """
+    Convert YCbCr image back to BGR color space.
+
+    Args:
+        img_ycbcr (np.ndarray): Input image in YCbCr format.
+
+    Returns:
+        np.ndarray: Image converted to BGR format.
+    """
     img_ycbcr = img_ycbcr.astype(np.float32)
-    # to [0, 1]
+    
+    # Scale back to [0, 1]
     img_ycbcr[:, :, 0] = (img_ycbcr[:, :, 0] * 255.0 - 16) / (235 - 16)
-    # to [0, 1]
     img_ycbcr[:, :, 1:] = (img_ycbcr[:, :, 1:] * 255.0 - 16) / (240 - 16)
-    img_ycrcb = img_ycbcr[:, :, (0, 2, 1)].astype(np.float32)
+    
+    img_ycrcb = img_ycbcr[:, :, (0, 2, 1)]
     img_bgr = cv2.cvtColor(img_ycrcb, cv2.COLOR_YCR_CB2BGR)
-
+    
     return img_bgr
 
-
 def color_saturation(img, param):
+    """
+    Adjust the color saturation of the image.
+
+    Args:
+        img (np.ndarray): Input image in BGR format.
+        param (float): Saturation adjustment factor (1.0 = no change).
+
+    Returns:
+        np.ndarray: Saturated image in BGR format.
+    """
     ycbcr = bgr2ycbcr(img)
-    ycbcr[:, :, 1] = 0.5 + (ycbcr[:, :, 1] - 0.5) * param
-    ycbcr[:, :, 2] = 0.5 + (ycbcr[:, :, 2] - 0.5) * param
+    ycbcr[:, :, 1] = np.clip(0.5 + (ycbcr[:, :, 1] - 0.5) * param, 0, 1)
+    ycbcr[:, :, 2] = np.clip(0.5 + (ycbcr[:, :, 2] - 0.5) * param, 0, 1)
+    
     img = ycbcr2bgr(ycbcr).astype(np.uint8)
-
     return img
 
-
 def color_contrast(img, param):
-    img = img.astype(np.float32) * param
-    img = img.astype(np.uint8)
+    """
+    Adjust the contrast of the image.
 
-    return img
+    Args:
+        img (np.ndarray): Input image in BGR format.
+        param (float): Contrast adjustment factor (1.0 = no change).
 
+    Returns:
+        np.ndarray: Contrast-adjusted image in BGR format.
+    """
+    img = np.clip(img.astype(np.float32) * param, 0, 255).astype(np.uint8)
+    return img
 
 def block_wise(img, param):
+    """
+    Apply block-wise masking on the image.
+
+    Args:
+        img (np.ndarray): Input image in BGR format.
+        param (int): Number of blocks to mask.
+
+    Returns:
+        np.ndarray: Image with block masking applied.
+    """
     width = 8
-    block = np.ones((width, width, 3)).astype(int) * 128
-    param = min(img.shape[0], img.shape[1]) // 256 * param
-    for i in range(param):
-        r_w = random.randint(0, img.shape[1] - 1 - width)
-        r_h = random.randint(0, img.shape[0] - 1 - width)
+    block = np.ones((width, width, 3), dtype=np.uint8) * 128
+    num_blocks = min(img.shape[0] * img.shape[1] // (width * width), param)
+    
+    for _ in range(num_blocks):
+        r_w = random.randint(0, img.shape[1] - width)
+        r_h = random.randint(0, img.shape[0] - width)
         img[r_h:r_h + width, r_w:r_w + width, :] = block
-
+    
     return img
 
-
 def gaussian_noise_color(img, param):
-    ycbcr = bgr2ycbcr(img) / 255
-    size_a = ycbcr.shape
-    b = (ycbcr + math.sqrt(param) *
-         np.random.randn(size_a[0], size_a[1], size_a[2])) * 255
-    b = ycbcr2bgr(b)
-    img = np.clip(b, 0, 255).astype(np.uint8)
+    """
+    Add Gaussian noise to the image.
 
-    return img
+    Args:
+        img (np.ndarray): Input image in BGR format.
+        param (float): Standard deviation of the Gaussian noise.
 
+    Returns:
+        np.ndarray: Noisy image in BGR format.
+    """
+    noise = np.random.normal(0, math.sqrt(param), img.shape).astype(np.float32)
+    noisy_img = np.clip(img.astype(np.float32) + noise, 0, 255).astype(np.uint8)
+    return noisy_img
 
 def gaussian_blur(img, param):
-    img = cv2.GaussianBlur(img, (param, param), param * 1.0 / 6)
-
+    """
+    Apply Gaussian blur to the image.
+
+    Args:
+        img (np.ndarray): Input image in BGR format.
+        param (int): Kernel size for the blur (should be odd).
+
+    Returns:
+        np.ndarray: Blurred image in BGR format.
+    """
+    if param % 2 == 0:
+        param += 1  # Ensure kernel size is odd
+    img = cv2.GaussianBlur(img, (param, param), param / 6)
     return img
 
-
 def jpeg_compression(img, param):
-    h, w, _ = img.shape
-    s_h = h // param
-    s_w = w // param
-    img = cv2.resize(img, (s_w, s_h))
-    img = cv2.resize(img, (w, h))
+    """
+    Compress the image using JPEG compression.
+
+    Args:
+        img (np.ndarray): Input image in BGR format.
+        param (int): Quality factor (1-100, where 100 is highest quality).
+
+    Returns:
+        np.ndarray: JPEG-compressed image in BGR format.
+    """
+    if not (1 <= param <= 100):
+        raise ValueError("JPEG quality parameter must be between 1 and 100.")
+    
+    encode_param = [int(cv2.IMWRITE_JPEG_QUALITY), param]
+    _, img_encoded = cv2.imencode('.jpg', img, encode_param)
+    img_decoded = cv2.imdecode(img_encoded, cv2.IMREAD_COLOR)
+    
+    return img_decoded
 
-    return img
+def video_compression(vid_in, vid_out, param):
+    """
+    Compress a video using FFmpeg.
 
+    Args:
+        vid_in (str): Input video file path.
+        vid_out (str): Output video file path.
+        param (int): Constant Rate Factor (CRF) for quality control.
 
-def video_compression(vid_in, vid_out, param):
-    cmd = f'ffmpeg -i {vid_in} -crf {param} -y {vid_out}'
-    os.system(cmd)
+    Raises:
+        RuntimeError: If the compression command fails.
+    """
+    cmd = f'ffmpeg -i "{vid_in}" -crf {param} -y "{vid_out}"'
+    if os.system(cmd) != 0:
+        raise RuntimeError(f'Video compression failed for {vid_in}.')
 
-    return