Bitrate Advice

pmcross

pmcross

Pulling my weight
Jan 16, 2017
375
185
Pennsylvania
I’ve been having a disk latency issue recently that I believe has to do with running too high of a bitrate on my cameras. I’m looking to see what others run as their bitrate. I know that this varies by megapixel, etc. but I’m just looking for a common consensus from everyone to see if others run at the default bitrate or higher bitrates. I run all of my cameras on CBR and H264. My 3 MP cameras are running at 6,144 bitrate. My 4 MP is running at 8,192 and my 4K at 10,240.


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The question is NOT, what bitrate they run, the question is ON WHAT they save the streams/alarms!

I have 5x 4MP Dahuas, runs onto my Synology NAS DS918+ with 9TB net (Raid 1) with each max constant Bitstream = 8.192 = 5x 8.192 = 40.960 MBit = without an problem in a GbE network.

So, if you have problems with your target, lower the bitrate, or by a proper NAS.
 
Thanks for this @42er

The streams are saving to a SATA 3 6GB drive that is connected to an HP Z420. I also have gigabit NIC’s in my Z420.


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why do you think you are having a disk latency problem ? define the symptoms in detail.
 
My 4 k camera drops it’s FPS to 6 to 10 when it’s set to 15. That’s what tipped me off. I then started looking in resource monitor when I noticed that the queue length for the disk that I’m recording it spikes to 1 to 1.5.


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I run my cameras on VBR and let them do the work of picking the best bit rate for the moment. I have the image quality set to best and the max bit rate set to whatever the webui recommends.
 
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Thanks for this @aristobrat! Have you ever had any issues with the video being lower quality when motion occurs? I’ve read that VBR is the best option, but I’ve been hesitant because I’m worried that I may miss details from an important event.


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I haven’t noticed that. John from IPVM posted this in another thread:

john-ipvm said:
I am not sure which specific camera manufacturers you are referring to, but we test and track the major professional ones (from Dahua and Hikvision to Axis, Avigilon, Bosch, Hanwha, Panasonic, Vivotek, etc) and we rarely see such issues when using VBR. Moreover, in our surveys and tracking, VBR is the default used by integrators, again with rare, if any issues.

That said, I don't doubt that really low cost cameras may have problems but we also generally don't test them.
Click to expand...
 
Thanks again, I really appreciate the info. I’m going to change my cameras to use VBR and see if that helps my disk latency issues.


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@bigredfish out of curiosity, what do you run on your cameras CBR or VBR? Your night images are awesome, and I’ve read that night can cause issues with VBR, so that’s why I’m curious.


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looney2ns said:
John has also said that most people can't see any difference above 4 in the quality setting.
Click to expand...
Ah cool, I didn’t catch that. Guess I’ve got some more room for improvement!
 
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OP didn't mention what Software (BI, or other VMS) is being used for recording.
Or do you just have the cams pointed at your PC as a NAS or FTP server?

Also, gigabit NIC on the receiving server doesn't mean there isn't some other bottleneck on the network
IE, maybe you have too many cams/bits on a non-gigabit POE switch...

that said, your cam's bitrates add up to some 36864kbps, which should NOT saturate a 100mbps link, unless
there's other traffic or streams being duplicated, etc...
 
pozzello said:
OP didn't mention what Software (BI, or other VMS) is being used for recording.
Or do you just have the cams pointed at your PC as a NAS or FTP server?

Also, gigabit NIC on the receiving server doesn't mean there isn't some other bottleneck on the network
IE, maybe you have too many cams/bits on a non-gigabit POE switch...

that said, your cam's bitrates add up to some 36864kbps, which should NOT saturate a 100mbps link, unless
there's other traffic or streams being duplicated, etc...
Click to expand...

Sorry for not mentioning in my original post. I’m using BI to record. My switch is gigabit. I’ve excluded the network as the bottleneck. It was the disk that was getting saturated. I was using the same disk to run a few VM’s from as well as recording Sighthound. I ended up throwing another disk in and using the original disk just for BI. This seems to have helped.


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pmcross said:
@bigredfish out of curiosity, what do you run on your cameras CBR or VBR? Your night images are awesome, and I’ve read that night can cause issues with VBR, so that’s why I’m curious.

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Click to expand...

I run everything pretty much max bitrate, max FPS, CBR.

I'm certainly not experienced or knowledgeable enough to argue the point but on LPR cameras in particular at night where a car passes at 25-30mph occupying just 3-4 frames, I've had better luck with CBR. I want every frame I can get.
 
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bigredfish said:
I run everything pretty much max bitrate, max FPS, CBR.

I'm certainly not experienced or knowledgeable enough to argue the point but on LPR cameras in particular at night where a car passes at 25-30mph occupying just 3-4 frames, I've had better luck with CBR. I want every frame I can get.
Click to expand...

Thanks bigredfish, I ended up sticking with CBR as I’m concerned that I may miss an important event using VBR and I am also concerned about running in forced color at night with VBR. I’m intrigued by the concept of VBR though and like the idea of optimizing storage.


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Exposure (and IR at night) is what gets you a nice sharp image.
VBR does not skip frames. it just allows more compression if/when it can be applied.
I run my LPR cams at VBR 10FPS and have never felt like i've missed anything.
Cars go by up to 40mph or more on our residential street and i always get a plate...
 
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pozzello said:
Exposure (and IR at night) is what gets you a nice sharp image.
VBR does not skip frames. it just allows more compression if/when it can be applied.
I run my LPR cams at VBR 10FPS and have never felt like i've missed anything.
Cars go by up to 40mph or more on our residential street and i always get a plate...
Click to expand...

Agreed. I didnt mean to suggest that VBR skips frames. But I do think more FPS can be beneficial at night with tag cameras and faster moving cars.

Two random snaps from last night from each of my Z12 tag cameras:
 

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