Pelco Developer Network (PDN)

StreamControl Issues


Why does a playback or live stream seem to lag?

There may be multiple factors for the problem above. Here is one explanation:

The refresh rate of the monitor depends on the resolution displayed and the capability of the monitor, but US monitors are between 60 - 120 Hz. Just like the video framerate of a camera, the refresh rate of the monitor is factorialy related to the input power frequency; this is why in Europe you have 50/75/100/150 Hz Monitors and in the US you have 60/75/90/120 Hz Monitors. The refresh rate is important as its frequency indicates how often we can draw something on screen.

We have between 60 and 120 times per second to draw or "blit" something onto the screen. Lets take a refresh rate of 60 and apply it to our example below. If we have an monitor that refreshes at 60 times per second, then for each frame per second we have 2 chances to draw something onto the monitor screen. In order to avoid "tearing" the software will wait for a "V-Blank" (the empty signal at the "top" of the picture) to draw the frame. Once something is drawn onto the screen, it will stay there until something is drawn over it. Therefore if we manage to draw a frame of video, it will stay on the monitor until the next frame is drawn on top of it. As such, if we have less than full frame rate, say 15 or 1 fps, then the effect is that the previously drawn picture will hang around on the display until it it is time to draw the next frame and the GUI software does so.


FrameAdvance

This action is only applicable for DVR / NVR devices.

Also refer to the VOL Header Data section below as another issue related to this action.


FrameReverse

This action is only applicable for DVR / NVR devices.

Also refer to the VOL Header Data section below as another issue related to this action.


Play

In some cases, IP110 cameras may omit a response for the Play action.

Also refer to the VOL Header Data section below as another issue related to this action.


Reverse

This action is only applicable for DVR / NVR devices.

Also refer to the VOL Header Data section below as another issue related to this action.


Seek

This action is only applicable for DVR / NVR devices.

Also refer to the VOL Header Data section below as another issue related to this action.


SeekEvent

This action is only applicable for DVR / NVR devices.

Also refer to the VOL Header Data section below as another issue related to this action.


VOL Header Data

Older Pelco MPEG4 devices may only provide VOL (Video Object Layer) header data for approximately the 1st 60 frames. Newer devices such as Sarix, Spectra HD and NET5400 all send out SPS/PPS ( THe H264 equivalent of VOL) every iframe.