Video Card Roundup - DVD Quality, Features & Performance - October 2000

S3’s Return – Hardware Motion Compensation

In 1998, AnandTech as well as the rest of the eager hardware community saw the return of an industry giant to the limelight.  With the 3D(fx)-revolution of the past couple of years, manufacturers such as S3 that had no real 3D solutions and had depended on their line of 2D graphics accelerators to carry them had quickly lost purpose in the eyes of the quickly changing add-in graphics card market.  However S3 did make more than one attempt at regaining the ground they lost, such an attempt was in 1998 with the Savage3D. 

While the Savage3D ended up being an overall disappointment once it actually hit the streets, it did bring one very interesting feature to the table, Hardware Assisted DVD Playback or as S3 called it back then, and as we call it today, Hardware Motion Compensation. 

Part of why MPEG-2 compression works so well in terms of compression efficiency is because it removes a lot of the data that would otherwise be unnoticeable to the viewer.  For example, let’s take two scenes, one where an individual is standing still in front of a relatively stationary background and one where the individual is shifted to the left without any real changes to the background.  In an uncompressed video state, all of the data from those two scenes would be kept in their entirety.  However, any intelligent compression algorithm would say that it would make sense to keep one copy of the background data and simply shift the data corresponding to the individual being moved.  It’s the equivalent of refraining from reinventing the wheel in respect to video compression. 

This is what the motion compensation aspect of MPEG-2 compression entails, the translation of that object, or in the case of the aforementioned example, the translation of the individual from one position to the next. 

Normally, without any hardware decoder present in a system, this part of the MPEG-2/DVD decoding process is handled entirely by the CPU.  But since it is such a prevalent part of the decoding process it would only make sense to offload it onto some other part of the system, this is the opportunity that S3 saw when they introduced the Savage3D. 

While it wasn’t focused on nearly as much as it should have been during its time, the S3 Savage3D featured one of the first types of Hardware Motion Compensation on a PC graphics accelerator.  What this allowed to happen was one step of the decoding process to be offloaded onto the graphics chip, leaving more headroom for the CPUs of the time (Pentium II 400’s were the fastest things out around then) to work with when handling the rest of the fairly complex DVD decoding process. 

At the release of the Savage3D, no competing solutions offered any soft of Hardware Motion Compensation, not even the NVIDIA TNT2 that would quickly overshadow the Savage3D as the card to have.