Re: [linux-audio-dev] Setting the Beat of a Clock

On Sat, Sep 24, 2005 at 11:23:34AM -0400, CapnLinux wrote:

> I would like to build an application to assist in setting the "Beat" of
> a pendulum type clock. This is a tool used by a clock repair person to
> set a clock to keep accurate time. It is basically a low frequency
> oscilloscope with some specialized functionality.
>
> ...

Interesting project. I see one problem: the sample rate on most audio
hardware is much less accurate than what would be required for a clock.
That means that either you must use the computer's real time clock
(not extremely precise either), or some external timing reference,
e.g. a 1 Hz pulse from a GPS receiver, or a reference frequency.
In either case you would need to relate the audio clock the other
one. Since there is significant jitter on the only observation of
the audio clock you have (audio card interrupts as seen from user
space), the only solution is use a delay locked loop to filter out
the jitter and find the exact relation. I write this sort of thing
professionally, and if you need some help with this please feel free
to contact me directly.

-- 
FA