BLOb Cache breaks video in Media Web Part

Question

I have a Media Web Part on a page that displays video using Silverlight™. When I enable the BLOb Cache and enable it for the file extension my video file has, the video stops working and just says "Loading, please wait". If I disable the BLOb Cache or disable it for the particular file extension, it starts working again. I'm using Windows 7 on the client side.

Here's what I've concluded so far:

• The problem exists in all browsers
• The problem is not related to the max-age or to client-side caching: the problem exists whether or not the video file is actually downloaded from the server
• When the BLOb Cache is enabled, the video is served using GZip encoding (otherwise uncompressed)
• When the BLOb Cache is enabled, the video is served using chunked HTTP encoding (otherwise normal encoding)
• The video file is served to the browser correctly when the BLOb Cache is enabled (verified using Fiddler)

Here are my theories so far:

• This is a bug in Silverlight (relating to either GZip content encoding or chunked HTTP encoding)
• This is a bug in Windows 7 (relating to what, I don't know)
• This is a bug in SharePoint (not likely, since the video file is actually served to the browser)
• This is a bug in the Silverlight part of the Media Web Part (relating to either GZip content encoding or chunked HTTP encoding)
• The BLOb Cache actually doesn't support video (and this is not documented anywhere)

I'd like to know firstly whether this is reproducable by y'all, and secondly whether anyone has a theory or a citation on why it isn't working or whether there is a way to fix it. Currently, the "fix" is to disable the BLOb Cache for all video file extensions.

Answer 1

Don't forget that the blob cache also sets the max-age (default 1 day I think). You can set max-age to some small value in web.config to make sure that some front-end caching isn't confusing the issue.