10 sec NVR latency

[aurmol 0]

I'd like to understand the source of my 10 sec latency.

 

I connected my 802.11g Ipad to a 802.11n wifi router connected to a 4 channel nvr and get about 10 sec network latency (but only few millisecond monitor latency) so I'd like to understand where is the bottleneck.

 

As I understand it. An ip cam encodes raw video into H.264, then the nvr decodes back into raw for vga monitoring.. then it encodes it again into H.264 for recording?

 

Then when sending to internet.. it is the same recorded stream being sent out where the cms decodes back the signal to raw..

 

so I wonder if my 10 sec network latency is due to the recording encoding not powerful enough or the 802.11n not fast enough for it or the result of the built-in separate network of the dahua 10.1.1.1 POE. What is your guess?

 

What would happen when you try to record 4 channel of 1080p in an Nvr that can only take 2 channel of it. Would the recording hang or would it become very slow. In different brands. Do they show warning that maximum resolution exceeded or no warning and just maybe resize it to lower resolution automatically?

[MaxIcon 0]

Hard to say for sure, as different manufacturers code things differently. Some NVRs write the incoming H264 stream directly to the disk to save CPU, while others re-encode.

 

If the NVR adds info, like timestamps, it has to re-encode. If it's an inexpensive NVR, the CPU may not have the power to process a lot of data quickly, or it may not be processing the data into network packets quickly.

 

Which stream it sends out also depends on how the software is written. If it's sending out the same resolution, it may not re-encode, but if it's sending out a substream, it may be re-encoding that, or it may be getting it from the camera.

 

Do you also have a 10 second delay if you view the camera's output directly, rather than through the NVR?

 

You could also disable all the cams but 1, and if the performance improves, you may be CPU limited.

 

What kind of NVR and cams are they?

[aurmol 0]

Hard to say for sure, as different manufacturers code things differently. Some NVRs write the incoming H264 stream directly to the disk to save CPU, while others re-encode.

 

If the NVR adds info, like timestamps, it has to re-encode. If it's an inexpensive NVR, the CPU may not have the power to process a lot of data quickly, or it may not be processing the data into network packets quickly.

 

Which stream it sends out also depends on how the software is written. If it's sending out the same resolution, it may not re-encode, but if it's sending out a substream, it may be re-encoding that, or it may be getting it from the camera.

 

Do you also have a 10 second delay if you view the camera's output directly, rather than through the NVR?

 

You could also disable all the cams but 1, and if the performance improves, you may be CPU limited.

 

What kind of NVR and cams are they?

 

It's a 4 channel dahua NVR4204 with alleged 200Mbps bandwidth. I tested it for 2 hours a while ago. 3 ip camps of 1080p and one 960p were connected to all 4 channels at 30fps. Recording seems to be continuous as well as viewing thru vga (the dealer I bought this from never tested it at more than 2 1080p). But when viewing thru network connected to lan. There is a delay of about 20 seconds when viewing mainstream but only a few milliseconds when viewing substream. When I changed the fps to 10 and all 720p. The delay is about 10. It seemed the nvr can't handle network output (as live monitoring connected to the vga or hdmi has no problem). Now my questions to sort out the situation.

 

When an NVR sends out to network. How CPU intensive it is. Isn't it the stream is just send out to the Ethernet. Why is it slow? How much cpu power contribute to this versus just recording it?

 

Also dahua reported 200 Mbps incoming bandwidth for all 4, 8, 16 and 32 channels. Now why is that there is a 4 or 8 channel limit when the incoming bandwidth is the same (in other brands too). Is it because the decoders needed for vga/direct monitoring requirements? If so. Can you record more than 4 channels in a 4 channel NVR with the rest unable to view via monitor? Others?

[MaxIcon 0]

 

I've never run a Dahua NVR, and can't answer on how well it handles the streams, but others here have them and I haven't heard much about long delays like this. Maybe someone who's used this NVR can chime in.

 

Network processing is definitely part of the CPU load. How each machine handles this depends on how they wrote the code; some are better than others.

 

Many NVRs have similar hardware and are limited by the firmware to how many cams they can record; this is just something the vendors do. There might not be much difference except for POE ports and network boards. If it's a 4 channel NVR, that's all it will record or display due to firmware settings.

 

Try one channel and see if it improves.

 

You might also check to see if there's newer firmware available. Dahua firmware can be tough to find if your vendor doesn't support it.