生成时间越长，画质劣化越大

不是视频分块运行么，为什么前后会出现这么大的差异

<img width="321" height="247" alt="Image" src="https://github.com/user-attachments/assets/6bcf43de-de1e-4036-8789-34865b59cd1c" />

<img width="317" height="251" alt="Image" src="https://github.com/user-attachments/assets/6980db91-61d3-4edd-9b32-c78f1647a1de" />