On 7/26/13 12:50 PM, Didier Juges wrote:
There is a difference between managing the latency (as in ensuring that sound
and video are synchronized, but latency itself is acceptable) and minimizing
the latency as in a Morse code keyer where the operator has to manually control
the generation of elements that can be as narrow as 20mS (one dit at 60 words
per minute) while getting timely aural feedback. That means you need the sound
to start and stop within less than about 5 mS following the key closing and
opening.
It is trivial to do on a microcontroller running at 1MHz but surprisingly
harder to do on a 2GHz Windows machine.
It is not just a matter of time stamping the key closure, you have to get the
sound system starting and stopping.
Yep. although, since the propagation path is on the order of 100
milliseconds, providing feedback to the user directly from the interface
works quite well (e.g. generating tones directly from the keying).
The challenge is trying generate the sidetone through Windows. But
really, there's no reason why you can't have a "keying box" that
provides the direct side tone and sends the events to the host computer.
Then the issue is more about keeping constant latency (or else the CW
will be really, really hard to copy)
It's not like an extra 10 milliseconds of delay between keying and the
emitted RF waveform makes any difference at the other end.
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