Disable Windows XP File Caching

Background:

I have an application which plays video files from disc. When I play these files the first time the file reading sometimes lags. However, the second time it is played there is never any lag, I suspect this is because the file is put into the windows file cache the first time开发者_如何学JAVA it is played.

The requirements of my application is that it should be able to play any video at any time (the same video is almost never played twice, thus making the cache unnecessary), this makes the current problem quite critical.

In order to debug this problem I would need to disable windows xp file caching.

Question

Is there a way to disable windows xp file caching?

EDIT/More Info

Im using ffmpeg, and have no access to the actual file read calls. The problem can occur even if several other files have been played previously (warm up).

In general, you can't just force FILE_FLAG_NO_BUFFERING. It requires aligned buffers, and typically these aren't provided. Besides, it's the wrong thing. You don't care whether Windows reads 32KB ahead.

The only thing that you'd like Windows to do is discard file contents from cache after you've read them. The correct flag for that is FILE_FLAG_SEQUENTIAL_SCAN. This hints Windows that you (probably) won't seek back, so there is no reason to keep those bytes in cache.

You can try passing FILE_FLAG_NO_BUFFERING to CreateFile() to avoid caching. This imposes some requirements on your buffers. Specifically, their size must be a multiple of the sector size and their addresses must be aligned on the sector size. See MSDN for more details.

Assuming you have access to the CreateFile call which ultimately opens your file, you can use FILE_FLAG_NO_BUFFERING when you open it:

http://msdn.microsoft.com/en-us/library/aa363858%28VS.85%29.aspx

If you're not calling CreateFile directly yourself, but via some kind of library, you'll need to see if they provide a way to let you set this flag indirectly.

You might also find that the initial delay is caused by loading-up of the enormous number of DLLs which can make up the media stack in Windows, in which case altering the way the media file itself is opened won't help.

You could test this by making an extremely short media file, which you play at app startup, to 'warm-up' the stack.