Connectivity

Hi all !

i used NK-3G144.When i switching between 2 source HD : source 1 and source 2 (source pass thruogh CG) so have flash black in monitor.Compare to reference, source 1 delay 16 micro second ,source 2 delay 32 micro second.who can answer me that maximum delay source 1 with reference and max delay of source 1 with source 2.

Switching point is define in SMPTE RP 168 but it must purchase to read it.

Thank!

Hi Lee,

The router itself does not have a maximum delay specification. However, devices downstream from the router (such as your monitor) will have such a specification. Most broadcast monitors are very sensitive, even a small delay may cause them to glitch. Other devices such as WFM are aware of switching line, and can tolerate much larger delays. The exact value however varies from product to product.

Keep in mind that the NK-3G router does not have any line- or frame-sync; it cannot correct for mis-timed signals. It just cuts between the signals at the prescribed time, as defined by SMPTE RP 168.

Do check that your router has a valid reference signal, and that the switching line has been correctly set for either SD or HD format. Otherwise switching occurs at random point, which will cause troubles for downstream equipment.

Regards,

-Ralph

#NK

Hi Ralph !

If you have document of SMPTE RP 168 please sent me.

I thank that 2 source must delay < horizontal blanking ~ 9,6 micro second to work good for switching.

Thank !

#NK

Hi Lee,

I'm not able to share RP 168 unfortuantely. But I can tell you it lists different values for almost every video format. And this just defines where the switching line and switching point should fall. Each piece of video equipment interprets this somewhat differently.

The NK-3G routers perform what is often called a "timed switch". Based on the reference signal, the router cuts the video signal at the exact switching point as defined in the SMPTE spec. As there is only one reference, the router cuts all signals at this same point. If all inputs are the same video format, and they are timed perfectly, then the output from the router will also be clean -- downstream devices will not be able to tell.

But in practise, there is always some variation in timing. Thus the individual video signals will be cut "near" to the switching point, but not exactly. It is now a question of whether downstream equipment can handle such a mis-timed switch. Some devices will not tolerate even a minor (one pixel) shift. Others, like our MUX/DMX cards, are designed to handle +/- ½ line variation. There really is no single standard value here -- RP 168 is a recommendation, but not a hard requirement.

Depending on your needs, you might need to consider using either a line-sync or a frame-sync (possibly with clean audio switching) downstream of the router. It really depends what you are feeding into. Studio monitors tend to be quite sensitive, while many other downstream devices are more forgiving. Also if you are using some sort of SDI to HDMI conversion to drive your monitor, consider its specifcations as well.

Regards,

-Ralph

#NK

Hi !

Thanks for all that you said.

My system for SD but now i add 2 HD chanel.With SD used Black burst for system.but if have SD + HD we must used tri-level sync for HD (i think switching HD we can used black burst for HD but with xpression for HD support say me must used tri-level for xpression) so we used black burst for NK-3G and used tri-level for Xpression.can i do it . i need some advice.

can tri-lvel used for NK-3g with system SD + HD.

Thanks !

#NK

Hi Lee,

You can use either black burst or tri-level with all of the equipment (Xpression and NK-3G144). If you do use multiple reference formats, make sure they are generated from a single source, so that they are in sync.

Regardless of which type of reference signal you use, the NK-3G router has a user-adjustable switchpoint setting. This should be set to match the video format (SD or HD) of the signals you are switching.

In the case where you are switching [I]both[/I] SD and HD signals, it is not possible to switch them both at the correct point -- this is a hardware limitation of the NK-3G router. So if you select SD, then SD signals will be switched correctly, while HD signals will be slightly mis-timed. And vice-versa of course. Downstream equipment will have to cope with this.

There is also a custom switch point setting. This allows you to specify a switching point somewhere between the SD and HD values. This would mean that [I]all[/I] switches will be mis-timed, but in some cases, downstream equipment may be happier with this arrangement.

So to answer your question, you can use either blackburst or tri-level with your NK-3G, but if you use both SD and HD video, then at least one of them will not be switched at exactly the right point.

-Ralph

#NK

Hi !

With HD i think that need used tri-level because NK-3G switching in line 7.but if used black burst for NK-3G it not known start of line 7 of HD. black burst just used for vertical interval with HD.

am i right ?

Thanks !

#NK

Hi Lee,

The NK-3G supports both black burst and tri-level reference; regardless of the video format you are using. So even in HD formats, you may use black burst reference.

The NK-3G locks to the reference signal, and then performs all switches at a fixed time delay, relative to the reference. This delay is specified by the user - it is important that you set this parameter correctly. The choices are: SD, or HD, or a custom value in microseconds.

For details, please refer to the NG-3G144 user manual, page 44, "Setting up Video Referencing":

http://www.rossvideo.com/pdf/manuals/routing-systems/nk-3g144_user_guide.pdf

Regards,

Ralph.

#NK