Adding a GPU card, Does it help?
"The GPU’s advanced capabilities were originally used primarily for 3D game rendering. But now those capabilities are being harnessed more broadly to accelerate computational workloads." - NVIDIA
Short Answer : Yes. You just need to set the options to make use of it.
Requirements
FFMPEG 3.2+ is needed to use the HWAccel feature unless you have built FFMPEG manually with them. For Ubuntu users everything is easy. Just follow this guide and you will get what you need.
To check what decoders are available you can run the following in terminal.
ffmpeg -hwaccels
FFMPEG for Windows comes with CUVID but no VAAPI. In many articles I find that CUVID may be deprecated. Regardless it still works and performs real well with my Geforce GTX 970M.
Where are the options?
The options are exposed in the Pro version's dev branch and will be merged before the beginning of December. My own tests with CUVID were successful. My tests with VA-API were not. I welcome anyone to help with that.
How do I know HWAccel is in my version of Shinobi?
In your Identity section. For some Encoders you have to select a Decoder. Depending on your choice you will need to set a path to your GPU. For VA-API it is usually /dev/dri/renderD128. For CUVID it is left blank.
Go down to your Stream or Recording section and select the Video Encoder. You should see a whole bunch of options under "Hardware Acceleration". Select the one for your setup.
Why write this article?
I was inspired to write this article by this forum post found on the ZoneMinder website. The post was about this very question. Adding a GPU card, Does it help? Here is the response that was given by a ZM developer.
No. Assume you are running a server? GPU are for desktops. Add more RAM if you can. That is where you will gain the most. My i5 runs 17 cameras without a problem. - ZoneMinder Developer
This is incorrect. If you know NVIDIA then you might know about their Tesla line up. They are a line of GPUs with no display ports which are designed specifically for servers. Built for purposes such as this.
The correct response in relation to ZoneMinder would be as follows.
No, At this time ZoneMinder cannot make use of GPUs. Maybe in the future.
I did post on the forum correcting him but all it got me was my post being deleted and my account being banned for "spamming". Seriously.
Luckily another user corrected the developer, sadly almost a month later though. In that time numerous people have already absorbed the initial response because a developer of ZoneMinder told them so.
The name "ZoneMinder" holds power. With that in mind most people will implicitly trust the developers in these matters. I was one of those people.
Beware of false knowledge; it is more dangerous than ignorance.