Bitrate settings

[Beemster]

Hello everyone!

Last year I bought 3x the Hikvision DS-2CD2155FWD-I via use-ip. I use the internal SD card to store the recorded video.

Some settings do not make much sense to me, and how they affect the performance of the camera when turned up or down. These are the 3 settings I am talking about: Bitrate Type, Max bitrate, Max average bitrate.
Unfortunately, the Hikvision manuals are not that detailed, and therefore I hope you guys can help me out.

In the video settings, I use the maximum resolution (of course) 3072 x 2048. Quality of video set to the highest, using 20 fps, using H265+ (see picture attached, sorry in Dutch).

Why should I, or should I not, use Variable Bitrate?
What Max Bitrate should I use? What if I set it too high or too low?
What Max Average Bitrate should I use? What if I set it too high or too low?

Thank you for your help, and I do apologize if this question has been asked before somewhere in the forum.

 

[Dan]

Hi @Beemster

It is a common area of confusion for lots of customers, first I should quickly explain the 3 different bitrate options that you will find when dealing with network cameras:

CBR stands for constant bit rate, aims for a constant or unvarying bandwidth level with video quality allowed to vary
VBR stands for variable bit rate and allows the bit rate to vary but maintains a constant video quality level
MBR stands for maximum bit rate allowing the bit rate to vary but only up to a maximum value, effectively VBR with a cap.

So, with your 2155 camera what you have is CBR and MBR, it does say variable but as you still have to set a max. bit rate it is actually an MBR. We usually recommend that people use VBR or MBR as these are the options that have the least effect on the video quality, it is unfortunately tricky via the browser access to get live information on how high the bit rate is going (the direct monitor GUI does have a menu that gives you this information live) but with H.265+ compression enabled you will be reducing the bitrate camera produces so it is unlikely that you will set the bit rate too low. We have an NVR in the office with a 5MP camera connected and even when that camera was dealing with fast motion it was not producing much more 600Kbps so setting the Max. bitrate somewhere between 2,000-4,000Kbps will be more than enough for one 2155 5MP Dome. (This only the cap on the bitrate so setting this too high is not really an issue)

The average bitrate is not something we have come across before, but I would say it is not as crucial as the max. bitrate and is likely only a mid-range figure of bitrate that you would be expecting the camera to use most of the time but I don't think this measurement will actually have any effect on the quality of video output.

The CBR option would only be used if you had slow internet/limited bandwidth capacity and it is not possible for you to have the cameras bitrate fluctuate as this would be too much for the bandwidth capacity of your local network, but with H.265+ compression and most people having high-speed broadband connections, bandwidth limits are not really an issue.

 

[Beemster]

Thank you Dan for your swift reply and the clear explanation! The different settings make sense now ;-).

 

[fullboogie]

On my setup, average bitrate is a reporting function, not something you can change.

Dan will correct me if I'm wrong, but max bitrate is only useful for setting a top threshold. Meaning, if you want to restrict your bitrate to something lower than what the camera is capable of producing, you can do so. But if your camera only produces let's say 2,000 kbps and you set it at 8,000 kbps, it does not force that higher bitrate. It only raises the ceiling on what is possible.

 

[Dan]

On my setup, average bitrate is a reporting function, not something you can change.

Dan will correct me if I'm wrong, but max bitrate is only useful for setting a top threshold. Meaning, if you want to restrict your bitrate to something lower than what the camera is capable of producing, you can do so. But if your camera only produces let's say 2,000 kbps and you set it at 8,000 kbps, it does not force that higher bitrate. It only raises the ceiling on what is possible.

Yes @fullboogie you are correct, the max. bitrate is simply a cap on the bitrate and only has an effect on your recording if the bitrate the camera is producing surpasses the max. bitrate you set. Max. bitrate and average bitrate have no effect on the bitrate/amount of data produced by the camera.