[Media type] To make new filetypes available for uploading you need to declare class for each type. #episerver #c#

VideoFile.cs

using EPiServer.Core;
using EPiServer.DataAnnotations;
using EPiServer.Framework.DataAnnotations;

namespace SomeName.Project.Media
{
    [ContentType]
    [MediaDescriptor(ExtensionString = "flv,mp4,webm,ogv")]
    public class VideoFile : VideoData
    {
        public virtual string AlternativeText { get; set; }
    }
}