diff --git a/.gitignore b/.gitignore
index df338eb..0d13db6 100755
--- a/.gitignore
+++ b/.gitignore
@@ -352,4 +352,5 @@ $RECYCLE.BIN/
 *.ass
 *.xml
 *.png
-printdens.py
\ No newline at end of file
+printdens.py
+*.mp4
\ No newline at end of file
diff --git a/README.md b/README.md
index aaa08fc..ad9d3a1 100644
--- a/README.md
+++ b/README.md
@@ -6,11 +6,32 @@ Auto slice the shorts based on the density of danmaku.
 
 - Detect the dense period of danmaku based on the sliding window algorithm.
 - Slice the video based on the density of danmaku.
-- Support GPU accelerated calculation.
+- Support GPU accelerated calculation.(Automatically choose whether to use GPU acceleration)
+- Support custom quantity slicing videos.
+- Support custom slice duration.
+
+## Prerequisites
+
+To use this tool, you need to install ffmpeg first.
+
+- Windows: `choco install ffmpeg` (via [Chocolatey](https://chocolatey.org/)) or other methods.
+- macOS: `brew install ffmpeg` (via [Homebrew](https://brew.sh/)).
+- Linux: `sudo apt install ffmpeg` (Debian/Ubuntu). 
+
+More OS please refer to the [official website](https://ffmpeg.org/download.html).
 
 ## Usage
 
+### cli usage
+
 ```bash
 python -m autoslice.autosv
 ```
 
+### api usage
+
+```python
+from autoslice.autosv import slice_video_by_danmaku
+
+slice_video_by_danmaku(ass_path, video_path, duration=300, top_n=3, max_overlap=60, step=1)
+```
diff --git a/autoslice/autosv.py b/autoslice/autosv.py
index 7d3bcc7..d12f1ce 100644
--- a/autoslice/autosv.py
+++ b/autoslice/autosv.py
@@ -1,6 +1,8 @@
 # Copyright (c) 2025 auto-slice-video
 
+import os
 from .calculate.selection import find_dense_periods
+from .slice.slice_video import slice_video
 
 def parse_time(time_str):
     """Convert ASS time format to seconds with milliseconds."""
@@ -19,6 +21,28 @@ def extract_timestamps(file_path):
                 timestamps.append(start_time)
     return timestamps
 
-timestamps = extract_timestamps('./sample.ass')
-dense_periods = find_dense_periods(timestamps, 300, 3, 60)
-print(dense_periods)
\ No newline at end of file
+def slice_video_by_danmaku(ass_path, video_path, duration=300, top_n=3, max_overlap=60, step=1):
+    """
+    Slice the video by the dense periods of danmaku.
+
+    Args:
+        ass_path: The path to the ASS file.
+        video_path: The path to the video file.
+        duration: The duration of the slice.
+        top_n: The number of top dense periods to return.
+        max_overlap: The maximum allowed overlap between periods (in seconds).
+        step: The step size for sliding window (in seconds).
+    """
+    output_folder = os.path.dirname(video_path)
+    video_name = os.path.splitext(os.path.basename(video_path))[0]
+    timestamps = extract_timestamps(ass_path)
+    dense_periods = find_dense_periods(timestamps, duration, top_n, max_overlap, step)
+    print("The dense periods and their count are:")
+    i = 1
+    for period in dense_periods:
+        print(f"Start from {period[0]} seconds with the count is {period[1]}")
+        slice_video(video_path, f'{output_folder}/{video_name}_{i}.mp4', period[0], duration)
+        i += 1
+
+if __name__ == "__main__":
+    slice_video_by_danmaku('./sample.ass', './sample.mp4', 300, 3, 60, 1)
\ No newline at end of file
diff --git a/autoslice/calculate/selection.py b/autoslice/calculate/selection.py
index f3fa1d6..0f0f402 100644
--- a/autoslice/calculate/selection.py
+++ b/autoslice/calculate/selection.py
@@ -18,12 +18,12 @@ def check_cuda_available():
     except ImportError:
         USE_GPU = False
 
-def find_dense_periods(timestamps, window_size=300, top_n=3, max_overlap=60):
+def find_dense_periods(timestamps, window_size=300, top_n=3, max_overlap=60, step=1):
     """Find dense periods using either GPU or CPU implementation based on GPU availability."""
     if USE_GPU:
         print("Using GPU implementation")
-        return find_dense_periods_gpu(timestamps, window_size, top_n, max_overlap)
+        return find_dense_periods_gpu(timestamps, window_size, top_n, max_overlap, step)
     
     print("Using CPU implementation")
-    return find_dense_periods_cpu(timestamps, window_size, top_n, max_overlap)
+    return find_dense_periods_cpu(timestamps, window_size, top_n, max_overlap, step)
 
diff --git a/autoslice/slice/slice_video.py b/autoslice/slice/slice_video.py
new file mode 100644
index 0000000..753806b
--- /dev/null
+++ b/autoslice/slice/slice_video.py
@@ -0,0 +1,29 @@
+# Copyright (c) 2024 bilive.
+# Copyright (c) 2025 auto-slice-video
+
+import subprocess
+
+def format_time(seconds):
+    """Format seconds to hh:mm:ss."""
+    h = int(seconds // 3600)
+    m = int((seconds % 3600) // 60)
+    s = int(seconds % 60)
+    return f"{h:02}:{m:02}:{s:02}"
+
+def slice_video(video_path, output_path, start_time, duration=30):
+    """Slice the video using ffmpeg."""
+    duration = format_time(duration)
+    command = [
+        'ffmpeg',
+        '-ss', format_time(start_time),
+        '-i', video_path,
+        '-t', duration,
+        '-map_metadata', '-1',
+        '-c:v', 'copy',
+        '-c:a', 'copy',
+        output_path
+    ]
+    try:
+        result = subprocess.run(command, check=True, capture_output=True, text=True)
+    except subprocess.CalledProcessError as e:
+        print(f"Error: {e.stderr}")
\ No newline at end of file