I have embedded a windows media player in a asp.net web page, using the usual <object> and <embed> tags. The video is served by an ashx (http handler). When I try to play the video, I usually (but not always) get an error message telling me that the file extension (ashx) does not match the file format.
This happens in IE (8, 9, 10, 11) and also in Firefox (latest) with the WMP plugin.
I know that the tags (with classid, etc) are correct because the media player displays and allows me to click the 'play' button.
The ashx returns the correct mime type (video/x-ms-wmv) and a valid file name (somevideo.wmv) in the response headers. I have tried content-disposition attachment and inline.
I have tried urls using 'http://', 'https://', and '//' (which I prefer)
If I put the url (including the .ashx) of the video file in the browser address bar directly, the video downloads and plays in the standalone media player.
If I modify the object tag to use a direct path to the video file (/somewhere/somevideo.wmv), it works - but I can't use this as a solution.
The same ashx serves up video and audio in various other formats with out any fuss - it just seems that the embedded windows media player doesn't like it.
This has been working for several years - I think this is some new behavior, though I can't identify what has changed, other than browser updates.
Any ideas on what could be causing this? Am I missing something simple?