PPT document including Chinese characters are not get rendered

If we write a PowerPoint document in Chinese, it show messy code in Confluence when I try to preview it in browser.
Please see attachments, ChineseTest.pptx is the origianl document, messy-code.png and right-presenting.png are two snapshots, and right-presenting.png is expected.

BTW, this feature works well in Confluence 5.7.1.