6 Replies Latest reply: Feb 1, 2014 1:21 PM by dewdude RSS

    "No Video" on Composite Video input with RS170A video


      I hooked up a standard definition professional (RS170A) color bar generator to the video input of the SB 350. All monitoring site (newwatch) and software options report "NO VIDEO". If the system doesn't pass the official, standard definition professional NTSC video standard, what standard does it adhere to?

        • Re: "No Video" on Composite Video input with RS170A video
          dewdude Newbie

          I found this little blurb on the Apple site of all places:



          RS-170 is sometimes described as "the interlaced 60Hz video signal
          standard used for broadcast video in America."

          This statement is a little misleading.  RS-170 has not been the broadcast
          video standard in the United States for more than twenty years. RS-170,
          drafted in 1957, is a video signal developed by the Engineering Industries
          Association as a standard for monochrome (black and white) television
          studio facilities.

          RS-170 can be recorded using the "Video In" jacks of most video tape
          recorders. The Macintosh II Video Card can generate a signal that is very
          close to the exact specifications of the RS-170 standard--close enough so
          that it can be displayed on most RS-170 monitors, recorded on most RS-170
          video tape recorders, and so on. Unfortunately, the minor deviations from
          the exact standard causes problems with some video equipment.

          Twenty years after the drafting of RS-170, the EIA video signal standard
          proposal RS-170A evolved into what is known today as NTSC.  NTSC is the
          color television standard of the National Television Standards Committee,

          and is the standard now used for broadcast video in America.  This
          standard is the result of combining three RS-170 signals into a single
          encoded color video signal.

          While RS-170 signals are compatible with most of today's NTSC video
          products, it is NOT broadcast video, NTSC video, or color video.  Not
          knowing this fact can lead to confusion.

          Well, for starters, RS-170 is not NTSC standard.


          Without knowing the model of your generator, it's not possible to know wether it's outputting an actual NTSC signal or not. It's entirely possible it's outputting what's known as "double-strike" NTSC; which discards the even fields and generates essentially a 240p signal. This is a valid video mode, but was not allowed to be used for broadcasting; it was however used on old gaming consoles and was accepted by the majority of analog TVs. The Slingbox will likely not respond to anything but a proper interlaced signal. Most digital TV's have issues with 240p double-strike.

            • Re: "No Video" on Composite Video input with RS170A video

              I'm grateful for your insight. I retired in 2008 after just under 50 years as a network television engineer. The color bar generator I am using is a Grass Valley RS-170A (absolutely) full and split 75% bar generator. It is a broadcast standard NTSC generator.


              I recently returned to Slingbox that wouldn't pass the color bars and got another one which works fine.


              Thanks for your response.

                • Re: "No Video" on Composite Video input with RS170A video
                  dewdude Newbie

                  Yeah. I used to work on obscure equipment and had a guy bring in his color bar geneator/test pattern box because he couldn't use them on his LCD TV and thought they were broken. Turns out they were outputting 240p double-strike which the TV didn't accept as a valid input; conected to the analog CRT in the shop and it worked just fine.


                  Glad you got it sorted out; though I don't know why you'd try color bars unless it wasn't working with the cable box first. RS-170A isn't a model number I found and Grass Valley made a lot of portable sync generators to know if this was the case or not. It wouldn't surprise me if they didn't output full 525 interlaced since unlike PAL, you don't need the second field to know if your colors are going to be adjusted properly.

                    • Re: "No Video" on Composite Video input with RS170A video

                      Again, thanks for your response. I didn't mean to mislead you. The model number was not "RS-170A". It outputs a RS-170A color bar signal. It is part of a Grass Valley Model-100 switcher and was an add-on for that device. We used that switcher to broadcast the Presidential Inaugurals and Senate/House hearings throughout the 70's and 80's. I inherited it when we got rid of all our standard def equipment in favor of high-def. It absolutely puts out 525 line, interlaced video. That is NTSC.


                      I hooked it up because I had tried the output of my Verizon PVR, Sony Blue-Ray player and a VGA to composite converter with no joy. I confirmed with a scope that all three were conforming to NTSC broadcast standard definition video specs. The color bar generator was my final test to be sure I had been thorough in my testing of the Slingbox before I went to the trouble of returning it.