Normally, Adobe Experience Manager (AEM) Assets detects the MIME type of assets that you upload from their file extension.
If you use Apache Tika to upload assets, AEM Assets detects their MIME type from the content stream during the upload operation instead of the file extension.
This feature is disabled by default. To enable the feature, configure the Day CQ DAM Mime Type service from Configuration Manager.
MIME type detection using the Apache Tika library is a resource-intensive operation.