webconfig里的mp4代码,删除iis8可以正常work
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="3000000000" />
<fileExtensions>
<add fileExtension=".mp4" allowed="true" />
</fileExtensions>
</requestFiltering>
</security>
<staticContent>
<mimeMap fileExtension=".mp4" mimeType="video/mp4" />
</staticContent>