That's not true. libjpeg-turbo is ~50 MB/s last I tried - plus it's not lossless. fjxl and fpnge are basically an order of magnitude faster than that. libjpeg-turbo isn't even the fastest jpeg codec - you should check out the (relatively obscure) libmango - roughly 1 gbps decode on a 2020 macbook pro - or nvJPEG for GPU-based JPEG decoding. Supposedly there's even faster GPU-based decoders than nvJPEG, too.
I've written an open-source driver for the decoding side of the nvjpg module found in the Tegra X1 (ie. earlier hardware revision than the one in the A100).
I did some quick benchmarks against libjpeg-turbo, if that can give you an idea. I expect encoding performance would be similar.
Probably quite a bit, I don't know. The typical use case is to load up thousands of JPEGs at once to get good throughput despite copy overhead. You can see here the benchmark against jpeg-turbo: https://developer.nvidia.com/blog/leveraging-hardware-jpeg-d...
