Hi,
The 404 response here will be returned if the request to the source resulted in a non successful response.
I noted in your other forum post, Mediacache - caching is not useful, that you have implemented a custom MediaCacheRandomAccessReader class and are adding the variables to the url in the init method of that class.
When your class calls init for the main MediaCacheRandomAccessReader, the Media Cache should send a HEAD request to the source and is expecting a 200 response along with the file size. If it doesn’t receive a valid response, it determines that it cannot access the content and a 404 message is logged and returned to the player.
Roger.