Today I did a comparison of the playback display rate in various versions of Vegas Pro with GPU acceleration disabled and enabled.

The generated media test was JohnnyRoy's rendertestjr.veg linked in this thread.

The HDV and MP4 tests were 3 tracks of the media with audio, each with a Color Curves FX on it. The top 2 tracks had rotating pan/crop and 50% opacity. The top track of the HDV test also had a Bump Map FX on it. In other words, pretty tough tests and much more severe than my usual projects. I didn't do any 4K as VP10 doesn't really read my UHD media properly.

My GPU is an AMD Radeon HD 6970 with driver version 15.201.1151.1008.

Here were my results. "CPU" is with "GPU acceleration of video processing" disabled. "GPU" is with it enabled.

There was a "bit of a ramp up" after pressing Play, typically a second or two, before the stated speed was achieved in most cases. Impossible to measure.

Some conclusions:

• For these type of media, playback rate hasn't changed significantly in the last 3 versions.
• CPU-only HDV playback was a little faster in VP10 than subsequent versions
• CPU-only AVC/MP4 playback was a little slower in VP10 than subsequent versions
• GPU-acceleration of video processing makes an enormous difference. As the figures show, I actually didn't manage to formulate a test that would slow it below full frame rate.
• The HD 6970 is doing a great job, despite being so old. It's also running 3 displays besides doing the acceleration.

p.s. My comparison of project opening times is here.