[time-nuts] Time Code generator

[Magnus Danielson]

On 12/09/2010 02:46 PM, jimlux wrote:
> Magnus Danielson wrote:
>> On 12/08/2010 07:18 PM, jimlux wrote:
>>> Chris Albertson wrote:
>>>> Adding time code to video would be redundant. All video is already
>>>> time coded.
>>> All *digital* video is timecoded..
>>
>> No, not all digital video. The time-code is optional in many of the
>> transfer formats.
>
> You're right.. I was thinking more that analog certainly isn't always
> timecoded, but at least for digital, there's an inherent frame counter,

There is as inherent frame counting in the analog PAL and NTSC signals 
as there is for their digital counter-part in SDI.

> and dropped/doubled/partial frames are unusual in digital video systems.

Not after the frame-store farm...

> They're positively frequent in analog systems (esp consumer vhs!) But
> you'd still get caught if the frame rate isn't the same across your
> system (which is often the case)

Inside a production location yes, as the house clock dictates the time 
for all equipment... but not between the production locations, the 
solution being the use of a frame-store farm to "clean" the incoming 
signal into the local house-clock phase and frequency.

A number of false starts to align things to GPS have been attempted, but 
there has been some speed in the development. One progress was the 
definition of the SMPTE EPOCH in SMPTE 404M (which bounced the trial 
publication after feedback from a time-nut asking what time-zone the 
midnight of 1 Jan 1958 was being referenced, naturally it was UTC 
midnight which was intended and thus the Zulu time-zone). The idea with 
the SMPTE EPOCH (defined to where TAI and UTC align up) is that all 
sample-rates, line-rate, frame-rates etc. for all signals has T=0 at 
that time and then just follow the development of TAI, while the time of 
day would follow UTC.

> Consumer gear also usually doesn't have any ability to gen-lock.

Unfortunately. Some of it is hackable thought.

>>> It's been 12 years since I sat in an edit bay, so I'll bet that analog
>>> gear is pretty much out of the picture by now, though.
>>
>> Analog black-bursts is still here.
>
> I think that's the video equivalent of the 10MHz reference distribution.

It is.

Cheers,
Magnus