Hardware Transcoding Enabled but 100% CPU Usage?

General Discussions
1

I’m testing hardware acceleration on a low-end Kaby Lake Celeron (G3930, which has QSV support) on Win10. I’ve run into a weird issue. Plex Server confirms that it’s hardware decoding/encoding a file:

Plex Web (Microsoft Edge)
Playing
Converting 
Video Transcoding HEVC (hw) to H264 (hw) 
Audio Transcoding DCA to AAC

But when I check the Task Manager, the CPU is floating between 90-100% usage, with most of that being the Plex Transcoder process. I can’t imagine the audio transcode process requires 100% CPU.

Is this normal? I’ve seen similar behavior on a quad-core Haswell i5 as well. If not, where should I look in the logs for more detail?

(This computer isn’t yet compatible with 1709, so there is no GPU section in the task manager to review)

Thank you!

2

Going to answer my own post after spending some time researching last night:

With Quick Sync enabled, the Plex server spikes to 90-100%… but only for the first 2-3 minutes. I haven’t researched why, but I’m guessing it’s immediately filling the buffer on the client, then doing real-time transcoding. Even on a low-end Kaby Lake Celeron, the CPU load is fairly minimal after the initial spike.

Also worth noting that I tested hardware encoding on a quad-core Haswell Core i5 system and a dual-core Kaby Lake Celeron last night. The Kaby Lake ran circles around the Core i5 with acceleration enabled. Not only was the video sharper, but seeking didn’t take 30-40 seconds with random failures. Very pleasant surprise, for a machine that cost less than $200 to assemble.

3

Mine is doing this as well. I can see that my nvidia 1070 gpu is going some sort of trans-coding as it has the plex transcoder process utilizing it. However, my intel 3770 cpu jumps from idle at around 15% to 100% when a transcode starts. I’ll give it more than 3 minutes to test if it goes down.

4

audo transcoding still does use the cpu, so even if you have HA for video, if you have a lower power cpu it still will have to keep up with high bit rate HD audio to > aac and/or eac3 or whatever.

And Hd audio conversion does use a bit more than say converting dts to ac3 or whatever lossy audio source.

Along with audio transcoding, transcoding 4k is a lot of IO, so your cpu/chipset/disk subsystem is going to be getting a large workout.

ie reading in a 4k stream, transcoding vid/aud on the fly, buffering, and sending it out to the client(s).