[time-nuts] GPS->audio interface

Lux, James P james.p.lux at jpl.nasa.gov
Sun May 10 23:47:59 UTC 2009




On 5/10/09 4:26 PM, "Magnus Danielson" <magnus at rubidium.dyndns.org> wrote:

> Lux, James P skrev:
>> 
>> 
>> On 5/10/09 12:15 PM, "Brooke Clarke" <brooke at pacific.net> wrote:
>> 
>>> Hi James:
>>> 
>>> You might want to get a KIWI-OSD, Video overlay of GPS precision time
>>> stamp.  It adds HH:MM:SS EEEE OOOO FFFFFF at the bottom of the image and
>>> so can be seen in every field.  They have also developed a way to
>>> calibrate the camera shutter in relation to the frame time by using a
>>> number of LEDs.  The main use if for star occulation timing.
>>> http://www.geocities.com/kiwi_36_nz/kiwi_osd/kiwi_osd.htm
>>> 
>>> Have Fun,
>>> 
>>> Brooke Clarke
>> 
>> Yes, but that requires getting access to the video stream, which isn't easy
>> in a "camcorder" environment.  Separate video recorders actually cost more
>> than camcorders.
> 
> What precision of anything do you need?
> 
> Expect 50-100 ppm oscillators in there.
> 

Yes, but probably fairly good in the short run, and if you were recording
almost any sync signal (e.g. The 1kHz sine) you could calibrate that out.

> 
> 
> 
> Recorded material is compressed. Consider how that affects your readout.
> Recorded material is said progressive/interlaced. This may not reflect
> how the CCD is snapshot and readout. You may not have the expected 1125
> or 750 lines per frame, and exactly what frame rate do you have?

I think that's something they'll need to experiment with...

Jim




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