Re: Measuring TV Delays With regard to: "On 02/01/14 20:33, Bill Hawkins wrote: > IIRC, the reason why NTSC has an almost 30 fps rate is that early > vacuum tube TV sets could develop heater-cathode leakage that > would put a black "hum bar" in the picture. Almost 30 allows the > bar to move through the picture in a 60 Hz power distribution > system. Seems like Europe would have had that problem."
Not Quite. Before Color transmission was introduced, The field rate and frame rate was exactly 60 fields/sec and 30 frames/sec, respectively. The Frame rate was shifted as a result of the change in the horizontal line rate, primarily to avoid interference with the FM sound carrier when color transmission was adopted . "In January 1950, the Committee was reconstituted to standardize color television. In December 1953, it unanimously approved what is now called the NTSC color television standard (later defined as RS-170a). The "compatible color" standard retained full backward compatibility with existing black-and-white television sets. Color information was added to the black-and-white image by adding a color subcarrier of 4.5 × 455/572 = 315/88 MHz (approximately 3.58 MHz) to the video signal. To reduce the visibility of interference between the chrominance signal and FM sound carrier required a slight reduction of the frame rate from 30 frames per second to 30/1.001 (approximately 29.97) frames per second, and changing the line frequency from 15,750 Hz to 15,750/1.001 Hz (approximately 15,734.26 Hz)." See Wikipedia http://en.wikipedia.org/wiki/NTSC#Lines_and_refresh_rate. BD Systems On Friday, January 3, 2014 5:29 AM, "[email protected]" <[email protected]> wrote: Send time-nuts mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of time-nuts digest..." Today's Topics: 1. Re: Measuring TV delays (Gregory Muir) 2. Re: Measuring TV delays (Frederick Bray) 3. Update on my previous note regarding NBS television timing reference experiment (Gregory Muir) 4. Re: Update on my previous note regarding NBS television timing reference experiment (Chuck Harris) 5. Re: Update on my previous note regarding NBS television timing reference experiment (Robert Atkinson) 6. Re: Measuring TV delays (David J Taylor) 7. Re: Measuring TV delays (Magnus Danielson) ---------------------------------------------------------------------- Message: 1 Date: Thu, 2 Jan 2014 15:45:07 -0700 From: "Gregory Muir" <[email protected]> To: <[email protected]> Subject: Re: [time-nuts] Measuring TV delays Message-ID: <0B9DF1E83D4E4B81AC3555E776EF9B6F@D32K5JC1> Content-Type: text/plain; charset="iso-8859-1" Not certain as to how NBS achieved the transfer of timing accuracy but it was not believed to be in the VITS interval. If I can recall, there was a special waiver (FCC/NTIA) that was required in order to run the experiment. And it required some esoteric hardware to decode the signal at the other end. Mind you, this project was for local timing information dissemination only and didn't relate to programming aspects. This project was above and beyond the use of the local transmitted television signal sync pulses that NBS was using to synchronize the Fort Collins atomic clocks with the Boulder ones. I do agree, for those of us who tend to dabble in the sub-yoctosecond world, :) something like this is would be a rather coarse approach. Greg On Thu, 02 Jan 2014 19:15:13 +0100, Magnus Danielson wrote: >Just to help confusing matters even more, SMPTE-12M time code (which is >what you can suspect to be in the TV-signal) and it's Drop-frame >algorithm causes a drift of time over the day, as the drop-frame >mechanism isn't perfectly aligning up to 30000/1001 frames per second >over the 86400s day. This requires the production-time to be jammed into >alignment regularly, such as every day (off-hour). With the evolving >standards, the halting mechanics of drop-frame correction is not >changed, but just standardized. The jamming mechanism is also used for >leap-seconds and DST change-overs. >So, in the US and other 30000/1001 frames per second countries (formerly >NTSC), encoded time is not going to be useful for precision work. For us >in the 25 frames per second world, we only need to jam for leap-seconds >and DST change-overs, but that is enough of an upset, but can be more >easily predicted with only a few handful of bits extra information. >I prefer using MLS measurement for audio delay measurement. If you do it >right, you get 20,833 us step resolution, as a result of the 48 kHz >sampliung clock. MLS delay measurement is trivial using the Analog >Precision test-set. >Cheers, >Magnus ------------------------------ ------------------------------ Message: 2 Date: Thu, 2 Jan 2014 15:05:23 -0800 From: Frederick Bray <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Cc: "[email protected]" <[email protected]> Subject: Re: [time-nuts] Measuring TV delays Message-ID: <[email protected]> Content-Type: text/plain; charset=us-ascii We have noticed the same problem on some channels with Charter here in southern Calif. As noted, there can be a problem with recordings as a result. F. W. Bray Sent from my CP/M phone! On Jan 2, 2014, at 9:48, Joe Leikhim <[email protected]> wrote: > Here in Orlando, Brighthouse seems to have a delay of some 10's of seconds > for program material while the cable box through some magic of the internet > seems to be on time. As a result, the last seconds of some recorded programs > are lost. ------------------------------ Message: 3 Date: Thu, 2 Jan 2014 16:31:02 -0700 From: "Gregory Muir" <[email protected]> To: <[email protected]> Subject: [time-nuts] Update on my previous note regarding NBS television timing reference experiment Message-ID: <13B252DFE48B4CCEB57547F602DEE962@D32K5JC1> Content-Type: text/plain; charset="iso-8859-1" I did a little digging and managed to find a paper on the original television time experiment which was authored by David Howe of NBS, now head of the Time and Frequency Metrology Group at NIST. It can be found at http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=2&cad=rja&ved=0CDYQFjAB&url=http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F3092613_Nationwide_Precise_Time_and_Frequency_Distribution_Utilizing_an_Active_Code_within_Network_Television_Broadcasts%2Ffile%2F9fcfd5089a1d534c56.pdf&ei=Ze_FUsrXJ-LsyQGY0oHYCw&usg=AFQjCNGw2wK-8_RYN98R_72AlRLcm2BAUA&bvm=bv.58187178,d.aWc(Google cached - whew!). I stand corrected in my assumption that the timing signal was not related to the VITS interval in the video signal. They actually were inserting the signal on line 1. At the time Mr. Howe was involved in the development of the hardware that was deployed in the field for the experiment. He stated that the received code provided unambiguous time to 12 hours, with a resolution of 1 nanosecond and long-term stability of 10 nanoseconds for 10-second averaging. It's rather odd as to why I can't remember the sordid details off the top of my head regarding a project that took place 42 years ago.... Greg ------------------------------ Message: 4 Date: Thu, 02 Jan 2014 20:58:08 -0500 From: Chuck Harris <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Subject: Re: [time-nuts] Update on my previous note regarding NBS television timing reference experiment Message-ID: <[email protected]> Content-Type: text/plain; charset=UTF-8; format=flowed I had one of the remote units for this system many years ago. I scrapped the unit and used the cute little 5" Sony Trinitron TV for many years... I think I still have all of the PCB's that did the line extraction, and phase locking... -Chuck Harris Gregory Muir wrote: > I did a little digging and managed to find a paper on the original television > time > experiment which was authored by David Howe of NBS, now head of the Time and > Frequency Metrology Group at NIST. It can be found at > http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=2&cad=rja&ved=0CDYQFjAB&url=http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F3092613_Nationwide_Precise_Time_and_Frequency_Distribution_Utilizing_an_Active_Code_within_Network_Television_Broadcasts%2Ffile%2F9fcfd5089a1d534c56.pdf&ei=Ze_FUsrXJ-LsyQGY0oHYCw&usg=AFQjCNGw2wK-8_RYN98R_72AlRLcm2BAUA&bvm=bv.58187178,d.aWc > (Google cached - whew!). > > I stand corrected in my assumption that the timing signal was not related to > the > VITS interval in the video signal. They actually were inserting the signal on > line 1. At the time Mr. Howe was involved in the development of the hardware > that > was deployed in the field for the experiment. He stated that the received > code > provided unambiguous time to 12 hours, with a resolution of 1 nanosecond and > long-term stability of 10 nanoseconds for 10-second averaging. > > It's rather odd as to why I can't remember the sordid details off the top of > my > head regarding a project that took place 42 years ago.... > > Greg _______________________________________________ time-nuts mailing list -- > [email protected] To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nutsand follow the > instructions there. > ------------------------------ Message: 5 Date: Fri, 3 Jan 2014 07:23:06 +0000 (GMT) From: Robert Atkinson <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Subject: Re: [time-nuts] Update on my previous note regarding NBS television timing reference experiment Message-ID: <[email protected]> Content-Type: text/plain; charset=iso-8859-1 Here in the UK we had a version of this for nearly 40 years. It was called Ceefax or TeleText. Chunky graphics with the time, weather and lots of other information. it was also used for closed captioning. see < http://en.wikipedia.org/wiki/Teletext?> It was the best generally available time source for years. ? Robert G8RPI. ________________________________ From: Gregory Muir <[email protected]> To: [email protected] Sent: Thursday, 2 January 2014, 23:31 Subject: [time-nuts] Update on my previous note regarding NBS television timing reference experiment I did a little digging and managed to find a paper on the original television time experiment which was authored by David Howe of NBS, now head of the Time and Frequency Metrology Group at NIST.? It can be found at http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=2&cad=rja&ved=0CDYQFjAB&url=http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F3092613_Nationwide_Precise_Time_and_Frequency_Distribution_Utilizing_an_Active_Code_within_Network_Television_Broadcasts%2Ffile%2F9fcfd5089a1d534c56.pdf&ei=Ze_FUsrXJ-LsyQGY0oHYCw&usg=AFQjCNGw2wK-8_RYN98R_72AlRLcm2BAUA&bvm=bv.58187178,d.aWc(Google cached - whew!). I stand corrected in my assumption that the timing signal was not related to the VITS interval in the video signal.? They actually were inserting the signal on line 1.? At the time Mr. Howe was involved in the development of the hardware that was deployed in the field for the experiment.? He stated that the received code provided unambiguous time to 12 hours, with a resolution of 1 nanosecond and long-term stability of 10 nanoseconds for 10-second averaging. It's rather odd as to why I can't remember the sordid details off the top of my head regarding a project that took place 42 years ago.... Greg _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ------------------------------ Message: 6 Date: Fri, 3 Jan 2014 09:04:10 -0000 From: "David J Taylor" <[email protected]> To: "Discussion of precise time and frequency measurement" <[email protected]> Subject: Re: [time-nuts] Measuring TV delays Message-ID: <D41F2731B4234019BFEBABADB9D940BA@Alta> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original From: Chris Albertson When they broadcast "live" TV like from a sports vent I wonder if the time code generated by the camera is preserved? But then even if it were the time might have been set manually to match the display on the camera operator's cell phone. Same for scenes with clacks in the background. Do you trust them to be on-time? They might even have ben intentionally set wrong to hide the transmit delay. ================================= Can't comment on the camera time-code, Chris, but I would hope it was centralised rather than being off the operator's phone! The clocks I mentioned, F1 races, do appear to be accurate (observations partially from being present at the event), and certainly /not/ skewed to compensate for broadcast delay. Other times are when you see "behind the scenes" and a control-room clock is visible. Usually these are centrally synced, and can give a fair impression of the broadcast delays. All this from UK television observations - and the programs don't have a "bleep offensive content delay" - no nanny state here! (Others may differ in that view - <G>) I recall what Alan Jones once called Michael Schumacher on live TV, and the adjective was edited out on the repeat broadcast. Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu/ Email: [email protected] ------------------------------ Message: 7 Date: Fri, 03 Jan 2014 13:28:04 +0100 From: Magnus Danielson <[email protected]> To: [email protected] Subject: Re: [time-nuts] Measuring TV delays Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Bill, On 02/01/14 20:33, Bill Hawkins wrote: > IIRC, the reason why NTSC has an almost 30 fps rate is that early > vacuum tube TV sets could develop heater-cathode leakage that > would put a black "hum bar" in the picture. Almost 30 allows the > bar to move through the picture in a 60 Hz power distribution > system. Seems like Europe would have had that problem. > > No need for it now, but it's like the QWERTY keyboard . . . Wouln't help that much, since the power-grids 60 Hz vary over more frequency, than the 1/1.001 offset gives, which is about 59.94 Hz, and over the coarse of a day it varies more than 60 mHz. Cheers, Magnus ------------------------------ _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 114, Issue 7 ***************************************** _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
