Subscriber Discussion

Frame Rate Sharing / Cuts - No Frames Left?

UM
Undisclosed Manufacturer #1
May 25, 2017

I'm embarrassed to ask this question, but I can't get it out of my mind. 

I went to a seminar from one of our manufacturers reps today, which was excellent. 

One of the manufactures gave a presentation about the high frame rate that their camera is capable of as compared to other manufacturers. His comments left me wondering if I have been wrong for so many years, and I need an answer.

Here's the scenario:

A typical camera is capable of 30 frames/second.

He asked this question: What happens to the frame rate if you turn on WDR.

Answer: It cuts the frame rate in half, (15FPS).

You program your VMS to record at (9 FPS).

That leaves you 6 FPS for everything else. (15 FPS for WDR, 9 FPS for recording = 24 FPS)

Your live stream is now 6 FPS because that is what you have left.

Now you have a customer log in through the web app, but there are no Frames left.

He acknowledged that some cameras have dual stream, so it's still possible, but he went on to say that his camera can do 60 FPS, and the next version coming soon will do 120 FPS. Given the FPS the new cameras can accomplish, you won't have any issues not having enough frames for whatever your situation is.

Is this how IP video works? Do the frames get divided out by the number of users live streaming and the recording server? I asked 4 respected industry associates this question today and they all had the same reaction I had, which is why am asking all of you. 

Is this correct, and if so, how many of us don't know it?

 

JH
John Honovich
May 25, 2017
IPVM

Now you have a customer log in through the web app, but there are no Frames left.

What??? :)

Let me say there might be a camera in the world built this way that there are a finite number of frames and once you use them, you are out, but that is not typical.

What happens to the frame rate if you turn on WDR.

Answer: It cuts the frame rate in half, (15FPS).

First, that is simply not true, in general. There are some cameras (notably some of the more recent higher end Sony cameras) that work that way but typically cameras can maintain 30fps when doing true multi-exposure WDR.

You program your VMS to record at (9 FPS).

That leaves you 6 FPS for everything else.

Again, that is simply not true, in general. Most cameras have at least some multi-streaming capabilities where they can handle this simultaneously.

there are no Frames left.

At some level of simultaneous video stream usage, you can overload the camera (and that threshold certainly varies across cameras). I have not seen a scenario where there are 'no frames left', what typically happens is that frame rate slows across streams so that a stream configured for 15fps may drop to 3fps, a stream configured for 3fps drops to 0.5fps, etc. Those numbers are not exact but just to give a sense of pattern. One can do a simplistic test of this by opening up 5, 10, 15 browser tabs with the same camera streaming video on each to see how it degrades / lessens frame rate on each.

Net/net, frame rate is not something that is typically a problem in modern cameras. It could be on less common occasions but nothing like you are describing from his presentation.

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UM
Undisclosed Manufacturer #1
May 25, 2017

John,

Thanks for the response. I'm hesitant to mention the manufacturer because they are one of the big one and I don't want to embarrass anyone, but that is exactly what he said.

Since they are coming out with a new chip that does 120 fps, it can handle all of the scenarios you could need, and you won't run out of frames.

JH
John Honovich
May 25, 2017
IPVM

Since they are coming out with a new chip that does 120 fps

One of the general trend in CMOS imagers is higher frame rate support, e.g., a few years ago 60fps started becoming more common, 120fps next, etc.

Surely there are some specialist applications that need such higher frame rates, but for the average user, it won't make a significant difference. Related: Average Frame Rate Video Surveillance 2016

U
Undisclosed #3
May 25, 2017
IPVMU Certified

There are some cameras (notably some of the more recent higher end Sony cameras) that work that way but typically cameras can maintain 30fps when doing true multi-exposure WDR.

But don't they still typically cut the max frame rate in half?

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JH
John Honovich
May 25, 2017
IPVM

No.

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U
Undisclosed #3
May 25, 2017
IPVMU Certified

ok, but there are quite a few out there. 

Consider Hikvision, from their catalog, the vast majority of cameras claiming non-digital WDR have half the max frame rate when WDR enabled:

 

 

 

JH
John Honovich
May 26, 2017
IPVM

Good counter example, note though those cameras are 30 true WDR / 60 WDR off, not 30 / 15 from the OP. Any other manufacturers?

U
Undisclosed #3
May 26, 2017
IPVMU Certified

Any other manufacturers?

Axis has several

Hanwha as well:

Note that this model does not mention anything about it in the spec, only in the user manual.

Maybe worthy of a new column in your - WDR Manufacturer Cheat Sheet and Camera Tracking?

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JH
John Honovich
May 26, 2017
IPVM

Thanks. Yes, @Ethan also update our WDR guide for that.

I suspect this is more of a trend with newer 60fps imagers because historically 30fps imagers with true WDR typically were 30fps with WDR on or off.

UM
Undisclosed Manufacturer #2
May 25, 2017

Yeah, that is just misinformation, or very old misguided information.

Even "dual stream" cameras is old hat.

The number of frames per second the camera can process is usually separate from the frames it can output.  I have worked with cameras that can stream live at 30 fps at a given resolution, then record to SD card at 15 fps, then record to NVR/VMS at another frame rate/resolution.

That being said, some cameras, often older ones will drop the frame rate with WDR on.  Most high end manufacturers/models will be running at 120fps or 60fps, so that with WDR on you get 60fps or 30fps out.  

The frame rate that streams out should be different than the internal fps that the camera processes.  (Yes, the camera may have a max frame rate with WDR on....)

Avatar
Jeffrey Hinckley
May 25, 2017

That was like Trump math.

I have 60 fps cameras (max) that I use that drop to 30 fps WDR (max).  The VMS takes in the fps you program it for.  WDR may limit the ability to access a secondary stream, though (if you are using one stream for live and one for recording).  Maybe this is what was meant?

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JH
John Honovich
May 25, 2017
IPVM

WDR may limit the ability to access a secondary stream

Jeffrey, which camera have you seen this with? I don't recall this being commonplace (i.e., turning on WDR impacting secondary streams).

AR
Alexander Ryltsov
May 25, 2017

Nerd-style comment.

Each camera has several independent budgets: CPU (used for most operations), GPU (pre-processing / encoding and maybe analytics), Ethernet (network packets).

With multiple streams there are 2 distinct cases:

  1. streaming different resolution / framerate (different uri)
  2. streaming same stream to multiple clients (same uri)

First case is less scalable, as it consume GPU budget that is typically most limiting, main stream is typically occupying half of it. There may be few more "secondary" streams with less resolution / rate. Some camera allow secondary streams to compromise main stream - that may be your case.

Second case is more scalable, as camera is using the same GPU unit for doing all except pushing data over network. That operation is consuming CPU budget (but most CPU can hold hundreds of connections) and Ethernet budget. The last is most important as typical camera is using 100Mbps channel, and with 2-8Mbps streams that mean ~25 clients. Of cause, multicast may be an option but that is another story.

To summarize - modern cameras are mostly GPU-bounded, and some of them may compromise main stream by secondary streams, but that is typically from bad design and/or wrong costs optimization. Most cameras can handle things properly.

Returning back to rep's calculations - they are inconsistent in one place: they are calculating FPS without resolution. That is ugly, as if you are not using reduced resolutions - why use independent stream. And with reduced resolution stream is using much less GPU budget (say storage stream is actual resolution ~ 2MP-4K, but web/live stream is VGA/HD). That is the logic behind the rule 50% GPU for primary stream - camera can hold several less-resolution streams with other 50% GPU.

UI
Undisclosed Integrator #4
May 25, 2017

Hey UI#1. You also need to consider the fact that most clients should NOT be directly streaming from the camera. They tend to pull their streams from the NVR/VMS for remote monitoring. So even if what the rep was saying happened to be true you shouldn't technically "need" those lost frames.

(Just my 2-cents)

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