While VBR is more efficient, the quality would be constant with CBR. VBR quality varies, depending upon the device, but
@Crazykiller said it was fine on the camera, so I'm sure it is.
You are correct that there is a model of Dahua NVR that comes with space for two HDD's. Below are some personal, curated notes I collected from this thread about Dahua NVR's.
Mark
Dahua NVR Information
Dahua 4K 8/16/32 Channel (Non-PoE) Network Video Recorder (Requires you to provide PoE power sources)
Dahua Site Information Link Data Sheet
Purchase Link: NVR5216-4KS2 ($238.00) NVR5232-4KS2 ($265)
Dahua 4K 16/32 Channel (PoE) Network Video Recorder
Dahua Site Information Link Data Sheet
Purchase Link: NVR5216-16P-4KS2 ($340.00) NVR5232-16P-4KS2 ($375)
If you get a NVR with POE built in, the NVR will create a separate network for your IP cameras. This can make it tricky to connect directly from your PC directly to the camera. You probably won't have a need to do that often once they're setup, but you'll probably need to do it frequently while you're getting things configured and tweaked properly.
Note these
do not come with hard drives; you must purchase them separately. You can manage the NVR (including viewing the cameras) from your PC by connecting via the NVR's web interface with IE. Or you can download a free program from Dahua called SmartPSS, which connects to your NVR for managing and viewing camera video.
Dahua NVR IVS Issues
Many IP cameras feature "smart event" detection, like line crossing, intrusion detection, etc, but for the most part, these camera features can only be used to trigger/mark recordings on the camera’s matching brand NVR. This is due to using proprietary commands and connection methodology between the camer and NVR. Dahua features Intelligent Video Systems (IVS), which and is a triggering system that alerts either the camera that an event (intrusion, tripwire, abandoned object, missing object, etc.) has occurred and causes a signal to be sent. A
Passive Infra-Red (PIR) sensor detects motion from objects that cause a thermal change, such as a warm body/object moving in front of it.
If you plan on using IVS or the PIR sensor with your cameras, there are issues how the Dahua handles this. The NVR makes separate recordings for these clips (which isn't a bad thing), but, there are 1-2 seconds of skipped audio/video at the beginning of these clips. It is a problem with the way Dahua implements their event recording algorithm in all their IP cameras and NVR’s. Unless Dahua changes how they record (and start new video files when the camera sends an iframe), I don't think this can be fixed. Alternatively, use one of the work-arounds mentioned in
this thread, some of which are mentioned below.
Work arounds include reducing the maximum time of the gap down to one second by changing (on the camera) the iframe interval to match the value of your FPS. By default, the camera's iFrame setting is 2x FPS, which means you can have to up a maximum of a two second gap. Another option is to turn off event video recording, keep continuous recording, and store a jpeg snapshot on event triggers (ivs, motion, etc.). This provides a time line of events you can look at when scrolling through the video recording.
When recording continuously, you can also filter by event duration: Go to Setup -> Information -> Log, then search for event only, and you will see a list of all the events by time and date. With begin and end time, I can find events that have a longer time-frame that may be worth checking, as the shorter time-frame events are mostly false triggers. This is one method I used to check events on cameras that I don't wanted to be alerted by unless I suspect some suspicious activity occurred.
Although Dahua IVS events will not work with
Blue Iris or any other NVR that isn't made by Dahua, Blue Iris supports its own advanced motion detection, which is pretty good.
