如何把afe获取到的16000hz pcm编码为8000hz的opus (AIS-2216)

### Checklist

- [x] Checked the issue tracker for similar issues to ensure this is not a duplicate.
- [x] Provided a clear description of your suggestion.
- [x] Included any relevant context or examples.

### Issue or Suggestion Description

如何把afe获取到的16000hz pcm编码为8000hz的opus，比较简单的办法，多谢。最好提供例子代码。