GeoVision EFD2100 + Zoneminder = TROUBLE

[canbikehere]

I have Zoneminder 1.31.39 (the 'storageareas' version from iconnor's PPA) running on my Ubuntu 16.04 machine. At the moment I have a Monoprice clone of a Hikkvision camera (which is working perfectly) plus this GeoVision EFD2100. The Hikkvision is a 3MP camera while the GeoVision is a 2MP. All cameras are hard-wired back to a quality HP POE switch.

I've been having quite a bit of trouble with the GeoVision camera....

I started with ZM 1.30.4 and the Hikkvision camera and got everything working great there. I am running Modetect on the substream and Nodetect on the main stream, linked to the substream. That has been working great; I get the low CPU load of the substream for analysis but still have the high res images when I want to review on the computer. I have the substream set to 6 FPS and the main stream set to 12 FPS on both cameras.

I set up the GeoVision camera the same way (stll on 1.30.4). The substream works perfectly; I get proper recordings, the frame rate is fine. The main stream frame rate is another story though - it'll start up at full speed but after a minute or so it'll drop down to a frame every few seconds. Zoneminder doesn't report any errors in the logs, I can still ping the camera with no change in response time. With Zoneminder running I can open the main stream in VLC and it plays perfectly smoothly at full frame rate, so the camera is definitely capable of sending the data, just seems like Zoneminder is having trouble asking for it.

I should mention the cpu usage of the zmc process capturing from the camera drops to almost nothing when the frame rate drops... I'm definitely not CPU bound.

I decided to try ZM 1.31 to see if it was any better. This also gave me the option of using libvlc for capture...

If I use ffmpeg or the built in 'remote' source the main stream is unusable
If I use libvlc I get a usable frame rate, though still below the camera's defined rate. CPU usage on my server is quite high - 140% on average for the zmc process (I have 6 cores for my ZM machine so there's still plenty to go around, but it's enough to cause the fans to speed up)

Any thoughts on what I can do here? "Use libvlc" is ALMOST an option, except that it seems like other features such as h264 passthrough aren't working properly with libvlc yet...

[canbikehere]

Some further troubleshooting / experimenting....

I can play the stream fine from both ffmpeg (using ffplay) and VLC on my Ubuntu machine...

The frame rate in Zoneminder for the MAIN STREAM appears to match whatever I set the 'Group of Picture(GOP) Size' setting on the camera to; if I set it to an I-Frame every 5 seconds, I get 1/5 FPS. I currently have it set to 0.25, I get 4 FPS. This is strange; it suggests zoneminder is only getting the I-frames from the video source...