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some information for DVB-T modulators

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drmocm 2024-07-11 13:50:17 +02:00
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Here are some tips on how to use the modulator
cards.
After you set the tuning parameter of the modulator you open the
/dev/adaptor<X>/mod<Y> of your modulator and write into it.
You should write a steady stream of transport packets with the
rate given by the modulation. The easiest way to keep a steady rate
is to write as much as the device will receive until it blocks. In that
way you ensure that the device will not get an underrun of data and
you can use the acceptance rate as a guide for you input rate.
All you should do is to correct the PTS of your transport stream according
to the calculated packet rate and use a buffer that assures that you are
always ready to write as sson as the modulator device allows it.
E.g you have a circular output buffer that you fill to say 50% and than start
writing into the device in a seperate thread. You feed the output buffer
with you input TS and see that it does not underrun, you may need to insert
empty packets to do that. The output thread should always have enough data
to write to the device as soon as it no longer blocks.