IPC-HDW5231R-ZE - Record Sub Stream2?

I tried searching the forums for an answer and couldn't find it. I'm hoping someone can chime in.

I'm recording 24/7 to my 4TB NVR at 1080p because it has enough space to store several days worth of footage.

Each cam has redundant recording to SD card as a backup. At 1080p and using SD cards between 64 GB and 128 GB, I'm obviously seeing that many fewer days are stored before the data is overwritten.

I was hoping to record to the SD cards at 1080p or 720p with even lower FPS, to maximize the use of limited storage space.

The problem is that Sub Stream1 doesn't have resolutions that go this high. Sub Stream 2 does, but I can't figure out how to record it.

Accessing the camera web interface directly, Storage --> Record Control lets you pick between "Main Stream" and "Sub Stream", but not Sub Stream1 or Sub Stream2 specifically.

I thought maybe disabling Sub Stream1 and enabling Sub Stream2 under Camera --> Video would force "Sub Stream" under Storage --> Record Control to record Sub Stream2, but it doesn't.

Has anyone figured out how to record Sub Stream2 or to have higher resolutions in Sub Stream1?

I suggest to do the 24/7 recording on nVR. On the SD cards configure the camera to record motion only for backup.

This is a solution, but not ideal when I would prefer to record 24/7 at 720p and lower FPS to the SD cards.

What's the purpose of Sub Stream2 if you can't record it?

Check the RTSP stream URL - if it has ?channel=0 (or something similar) change that to ?channel=1 or ?channel=2
I'm at work right now, can't verify/validate the exact syntax, but it's simply a different channel value (could be 101 or 102)
I believe Onvif Device Manager can help you here. It will fetch and display the stream URLs for you.

Thanks VorlonFrog,

I can see the option to select Main, Sub Stream1 or Sub Stream 2 under the camera's RTMP settings. But again, wanting to just record Sub Stream2 to the cam's SD card, I can't figure out how that's done. The option is just non-specifically Sub Stream, and it seems to correspond to Sub Stream1 being recorded.