What video transcoding tool is the fastest and has the best quality?

The transcoding speed mainly depends on your CPU, and the relationship with the software mainly depends on the optimization of multithreading by the software. Although NVIDIA's cuda transcoding is really fast, the quality is really not good unless your code rate is high.

If you have a good Intel CPU, you can display transcoding with CPU, which is also very fast. The quality is a little worse than pure CPU transcoding, but better than cuda in NVIDIA. And faster.

The general transcoding software is a format factory, but so far it does not support Intel kernel display acceleration, nor does it support multithreading very well. The transcoding efficiency under 8 threads is between 80% and 90%. But it works well.

The rest is mediacoder, which supports multithreading well and transcoding quickly, and also supports cuda and Intel nuclear display acceleration, but it is difficult to use.