Hello,
You can ensure this in Page_PreRender method in ~/CMSInlineControls/MediaControl.ascx.cs control. Particularly in following part of code:
else if (MediaHelper.IsFlash(this.Type))
{
CreateFlash();
}
You can either remove CreateFlash(); method and define full custom code for flash, or you can leave this method here and then just modify generated HTML code in this.ltlMedia.Text property after calling this method.
You can inspire by code for custom FLV object as described in
Defining custom media types article.
Best Regards,
Martin Dobsicek