What's the difference between H265, x265, x264, H264 and which of these uses GPU instead of CPU and how to use H265 GPU NVIDIA acceleration in ffmpeg?

Question

I'm not sure if x264/5 use CPU and if h264/5 use GPU and also if h265 is basically HEVC_NVENC for NVIDIA GPU acceleration. So, if you could give me more info about these encoding types it would be great. I understood that, summing up a lot, x26* use CPU and are slower but more accurate while h26* are the opposite but h265 is the most recent and optimal trade off. Furthermore, I was trying to convert a video using GPU acceleration and my question is:

Does the following command tell to the GPU to use h265 to encode a video holding the same audio and at upgrading it at its maximum video quality? Furthermore, are there other ways to express the same command?

ffmpeg.exe -hwaccel_output_format cuda -i "input" -c:v hevc_nvenc -preset medium -rc constqp -qp 0 -c:a copy "output"

Answer 1

H.264 and H.265 are video codecs for compressing image frames to video.

H.264 is a very widely supported standard that's been around a long time. It provides good efficiency. H.265 is a newer codec which can reduce your bandwidth requirements for a given quality by around a quarter to a third, for most videos. (Or, you can increase quality for the same bandwidth.) H.265 is a patent-encrusted cluster (even more than H.264), and there are currently three groups who claim you must license with them to use it.

I'm not sure if x264/5 use CPU and if h264/5 use GPU

x264 and x265 are open source encoder implementations of the H.264 and H.265 codecs. They run on the CPU.

and also if h265 is basically HEVC_NVENC for NVIDIA GPU acceleration

Yes, that's basically correct. GPUs with NVENC support can encode H.265 video.

Does the following command tell to the GPU to use h265 to encode a video holding the same audio and at upgrading it at its maximum video quality?...

No. Maximum quality would actually be lossless encoding, which is apparently supported .