Reading in Files HELP!!!!

Hi, I am currently using hmmio to read in data for a multimedia player. When I run my program is starts off fast but then starts to slow down. I pin pointed the problem to the part where i read in the data. I read in about 15 megs at a time, about 30 frames.

It starts off at about 500ms per read but then slowly goes to an occsillating effect where it takes 500 ms to read then it takes 4 sec to read and so on. Does anyone know why this is happening? here is my code(short version)

char * fileBuffer=(char *)malloc(15552000);
byte* YP=(char *)malloc(15552000);

/****other stuff****/

void OpenFile()
{
hmmio = mmioOpen("C:\\Documents and Settings\\mliu\\Desktop\\YUVPLAYER\\pond.yuv", NULL, MMIO_READ );

mmioSetBuffer(hmmio,fileBuffer,15552000,0);

mmioRead(hmmio,(char *)YP,15552000);
}

//***calculation and direct draw functions ****//

You want to read15 megs in 500ms, i.e. 30MB/s constantly. What media are you reading from?
If it is a single hard disk, the difference in speed is probably due to fragmentation of the file. It would also be affected by
- Hard disk cache
- Controller cache
- OS cache / efficiency of this
- available memory / swapping / memory fragmentation
- interrupt sharing between the controller and another card that is frequently accessed (common: graphics card)
- driver efficiency / bugs
- [ ... ]

I don´t know these libraries you are using, but it looks like a Windows program - Windows was not made for high-performance apps like yours

Some tweaking in the OS settings could eliminate your problem, but maybe not...

I'm reading in a video file in YUV 4:1:1 format. its about 300 megs for 600 frames. Its reading off a local harddrive(7200 rpm).

I have also tried using fread functions and ReadFile functions and they also resulted in the same problem.

I don't need to read at 30megs/s, I only need to read in at about 15meg/s(30 frames per sec). I know it can't be a hardware problem since a similar program developed by a software company can play this file smoothly.

Please help me out and let me know there is any way to stablize to read in.

Problem Fixed, for anyone who cares or has the same problem. Use CreateFile instead of hmmio. The when using ReadFile specify
dwFlagsAndAttributes as FILE_FLAG_NO_BUFFERING and FILE_FLAG_OVERLAPPED. That will make it much faster and stable.