Presenters can now upload video files (.mp4 files) directly through the Presentation Submission Form if "Symposium upload" was selected when customizing the form. However, unless the presenter added captions and other accessibility features to their video file, the video files will not have automated closed captioning.
Video submissions can still be uploaded through YouTube if "Youtube link" is selected instead of "Symposium upload". YouTube meets all accessibility requirements (automatic closed captioning, etc.) and automatically compresses content well for viewers with low bandwidth.
If presenters are concerned about publicly posting their videos on the internet, they can easily set the YouTube visibility settings on their video to "Unlisted" to ensure that only people with a link will be able to view their video. Instructions to set the visibility to unlisted are provided within the Symposium presentation submission form, and may also be found here.