Software decoders and CPU requirements
In the past, when computers were less powerful, decoding MPEG2 movies in
real-time required specialized hardware. Watching DVD movies on your pc was
expensive and complicated. With modern processors, however, this is no longer
the case. Today, all you need is a DVD-drive, a decent CPU and good DVD
software. Does this sound to good to be true? It is.
The source of the problem
While a dedicated hardware decoder only has to do one thing, decoding movies,
your CPU is involved in almost everything going on inside your computer. Even
though modern CPUs are fast, they can't do everything at once. The solution is
called multitasking. By rapidly switching between different tasks, the operating
system gives you the illusion of doing many things at the same time. Each
running task gets a small slice of CPU time before the CPU is handed over to the
next task. If your DVD decoding software doesn't get enough of those slices, it
won't have time to decode all the frames in your DVD movie at high quality. The
result, as you probably know, is dropped frames, stutter and other annoying
What can I do to prevent DVD decoding software from running out of CPU
time? There are a few things you should always do before watching DVD movies on
1. Reboot the computer before you begin to make sure the operating system is
2. Terminate all programs that aren't absolutely necessary (Ideally everything
except the DVD software and some system processes). Use WinTasks to terminate as
many processes as possible (Using WinTasks, you can terminate many background
processes that don't show up in the CTRL+ALT+DEL dialog, as long as these are
not system processes or anti-virus programs they can usually be stopped as well
for even better results). When you have terminated all unnecessary processes,
save the current process configuration to a preset (available in WinTasks 4.00
or later), this way you can simply click the preset button to stop and start the
right processes before playing DVDs.
3. Make sure you have the latest version of DirectX and DX Media.
4. Try increasing the priority of the DVD software. You may have to try a few
different settings before you find the optimal priority for your system.
Priority settings can also be saved to a WinTasks preset (version 4.00 or
5. Make sure you have the latest drivers for your DVD drive.
6. Lower you screen resolution and color depth to 800x600 and 16 bit color when
playing DVDs (32 bit color may be preferable on some graphics cards).
Written by Emil Malmberg, Senior Software Developer for