Well, without going into too much detail, once you start curve-fitting, you kinda have to do it on a per-bone basis, so your animation poses aren't going to be

Well, without going into too much detail, once you start curve-fitting, you kinda have to do it on a per-bone basis, so your animation poses aren't going to be sequentially placed in the data-stream. That means that your poses have to be re-formed before they can be blended into the higher parts of the animation system. When all your keys are aligned, your keys are effectively poses themselves, so blending them together can be done as you do the inter-animation blending, which is a lot more efficient. Again, it's totally worth it, especially if you have memory contraints, but not what I'd have tackled, given what they described. Edit: in the context of this article, compression and data-reduction are interchangeable terms. Converting a quantized value into 4 floats isn't free and constitutes the "decompression cost", same goes ith interpolation.