Codecs aren't parallel enough to work well on GPUs; parallelism in general hampers compression efficiency.
Anyway, audio resolution hasn't increased anywhere near as much as video resolution. 48 kHz sample rate, 16 bit sample depth per channel is still the highest reasonable, and we've had basically that since CDs.
Whereas internet video has gone from CIF to 1080p, a resolution increase of over 20x. And 4k is being pushed now for another 4x increase.
The point is that audio resolution peaked, and additional returns were negligible at best. Video has the same effect occur somewhere around 300 PPI at 6" view distance, 200 PPI at 12", etc - and between 90 and 150hz refresh rate. Color fidelity is also near its limits on some high end IPS panels.
Past those points, most people don't notice the difference, just like how most people don't notice the difference between 16 and 24 bit audio at 44.1 or 48khz sample rate. Once the vast majority of people no longer see a difference, the technology peaks. I think video is (finally) approaching that territory in the next 5 years, at least in 2 dimensions. I feel holographic 3d video will see a boon after that, and not the eye trick 3d crap we have now.
Anyway, audio resolution hasn't increased anywhere near as much as video resolution. 48 kHz sample rate, 16 bit sample depth per channel is still the highest reasonable, and we've had basically that since CDs.
Whereas internet video has gone from CIF to 1080p, a resolution increase of over 20x. And 4k is being pushed now for another 4x increase.