Image not smooth, jerky

[kokokoala]

I am fairly new to the ip camera world so I may not be using proper terminology. When watching live view or recorded on my two outdoor cameras. It seems like every second the image shifts slightly, or is jerky... not smooth. It happens at 3000kbps and even at 12000Kbps, with bitrate being "variable" and quality set to "highest". These are outdoor E series speed dome cameras, 2mp. Frame rate is 30. I tried making it constant and moving the smoothing bar over to the right and it still occurs.

Changing the resolution from 1920x1080 down to 1280x720p makes it slightly less noticeable, though still occurring.I have an indoor 1mp camera mini ptz from hikvision and it does not seem to have the same problem and its only running at 2000kbps bit rate, constant with highest setting. The only real difference I see between the indoor and outdoor is indoor has a higher i-frame interval of 50 vs the outdoor cameras of 30 and a smaller resolution of 1280x720.

Rather than playing with a whole bunch of knobs without really understanding what they are... what is the name for this behavior and what tweaks can I do to smooth out my image? Is it an indoor vs outdoor camera issue?

Thanks.

 

[MaxIcon]

This is caused by the i-frame setting. At 30 fps and an i-frame of 30, you get a new complete image once a second. All the other frames are updates to the original. When the new full frame updates, it's enough different from the previous one that it looks like a glitch or jerk. Some cams are more prone to this than others, but there's not much you can do about it except set a longer i-frame interval.

You can verify this by changing your i-frame to 60 and see if it changes to every 2 seconds. If it's still every second, something else is going on.

 

[pozzello]

That makes sense MaxIcon. If the issue is indeed due to the difference between (full frame X + N incremental changes) and full frame X+1, would it not make sense to try a SMALLER
i-frame interval? That way, there's less chance for accumulated error between the i-frames (at the cost of higher BW usage). IE, you can have a bigger error/jerk less often,
or a smaller error/jerk more often. If you can make the error small enough, that may be the 'smoothest' looking...

 

[Michelin Man]

The smaller I-Frame number does mean more 'key' frames/full frames and as you mentioned bandwidth. Going larger in number on the I-Frame interval means less I-Frames overall.

 

[MaxIcon]

Yes, more i-frames will make smoother video. By the time you get to i-frame=1, you're running in MJPEG mode, essentially, which requires a higher bit rate for good quality, but every frame is good if your bit rate is high enough.

Running fewer i-frames has the benefit of having the glitch happen less often, but if any p-frames get dropped or corrupted, it takes longer before the i-frame comes along to fix the image. With more i-frames, if the quality suffers from low bit rate, the glitch will be even worse, since the p-frame will be more pixellated due to less bandwidth available, and each i-frame will clean it up more until the next i-frame comes along.

With variable bit rate, bandwidth changes will depend on the detail of the image and how much motion there is, as well as the camera's firmware. You'd have to test it to see for sure. My old Vivoteks will go above the baseline bit rate setting on variable if they need to, while Hiks use the bit rate setting as a max and will only drop below it. At least, that's how it worked when I tested, back on 2013 era firmware. I haven't updated for a while, so that may have changed.

Best bet is to test it at whatever settings you end up liking, and record a scene with a lot of motion and detail. If you step through it frame by frame and there's no obvious quality difference between the last p-frame and the next i-frame, your bit rate is good.