Calculating bitrate of IP video

C

cds333

Young grasshopper
Jan 5, 2016
41
6
It seems that whatever I set the "max bitrate" to, the camera will use every bit of that whether I have the framerate set to 1fps or 20fps. Logic would dictate that 1/20th the framerate would use 1/20th the bitrate, but that is not the case. I realize why but the fact that they do not tell you what the optimal bitrate is for any given FPS is pretty stupid, especially considering that the default bitrate selected when you initialize the camera it apparently already constrained, resulting in a situation where you can dramatically lower the framerate but still not get any more storage space out of the SD card.

So what is the actual bitrate being used by a 2688x1520 video feed?

How can I calculate this based on the number of pixels, the codec, the quality setting, and the fps?

It would be nice if Hikvision would just give you this info instead of making you work backwards through blueiris stats page :(

Camera is Hikvision 2CD2442FWD-IW btw

Thanks very much!
 
cds333 said:
It seems that whatever I set the "max bitrate" to, the camera will use every bit of that whether I have the framerate set to 1fps or 20fps. Logic would dictate that 1/20th the framerate would use 1/20th the bitrate, but that is not the case. I realize why but the fact that they do not tell you what the optimal bitrate is for any given FPS is pretty stupid, especially considering that the default bitrate selected when you initialize the camera it apparently already constrained, resulting in a situation where you can dramatically lower the framerate but still not get any more storage space out of the SD card.

So what is the actual bitrate being used by a 2688x1520 video feed?

How can I calculate this based on the number of pixels, the codec, the quality setting, and the fps?

It would be nice if Hikvision would just give you this info instead of making you work backwards through blueiris stats page :(

Camera is Hikvision 2CD2442FWD-IW btw

Thanks very much!
Click to expand...

Hi cds333,

It would be easy if the camera transmitted in raw pixels, with each and every pixel being retained and transferred.

Due to compression ( H.264/H.265 ) as well as what you actual scene changes are - there is a significant amount of variation.

For the Dahua cameras the spec sheet lists min-max bit rates, so you can at least determine the max.
 
I was hoping you would not say that lol. I will have to sit down one day and try every possible combination of resolution, quality, etc and record the incoming bitrates in BI, I suppose
 
cds333 said:
I was hoping you would not say that lol. I will have to sit down one day and try every possible combination of resolution, quality, etc and record the incoming bitrates in BI, I suppose
Click to expand...

What's the purpose? Make sure you have plenty of storage space and no network bottlenecks and be done with it.
 
Is your camera set to VBR (Variable Bit Rate) or CBR (Constant Bit Rate) encoding? In CBR mode, the camera will try to always encode at the specified bit rate no matter what the other settnigs are.

In VBR mode the bit rate setting is supposed to be treated as a maximum limit. Typically in VBR mode you have an additional setting for the video quality (e.g. "High", "Medium", "Low") and you may need to choose one of the lower quality levels in order to actually see your streaming bit rate go down below the limit.
 
bp2008 said:
Is your camera set to VBR (Variable Bit Rate) or CBR (Constant Bit Rate) encoding? In CBR mode, the camera will try to always encode at the specified bit rate no matter what the other settnigs are.

In VBR mode the bit rate setting is supposed to be treated as a maximum limit. Typically in VBR mode you have an additional setting for the video quality (e.g. "High", "Medium", "Low") and you may need to choose one of the lower quality levels in order to actually see your streaming bit rate go down below the limit.
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But for VBR you take the chance of of the bit rate not ramping up fast enough right? Like if someone runs from out of view at full speed then the bit rate won't have time to ramp up and you will have a loss of detail right? I don't like to risk not having optimal quality in a time when it may be needed.
 
Philip Gonzales said:
But for VBR you take the chance of of the bit rate not ramping up fast enough right? Like if someone runs from out of view at full speed then the bit rate won't have time to ramp up and you will have a loss of detail right? I don't like to risk not having optimal quality in a time when it may be needed.
Click to expand...

I don't know how the encoders work internally well enough to know how they handle it. I just don't use VBR on anything where quality is important.
 
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