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Harald Welte laforge at gnumonks.orgHi Alexander and Max,
I don't really have to add anything to what Alexander wrote, but to make
it super-clear:
On Wed, Jun 01, 2016 at 10:51:47PM +0300, Alexander Chemeris wrote:
> Sequence number is incremented by 1 with every packet, even if the packet is
> sent after a long pause (due to DTX). This way you know when you miss a packet.
correct, and makes sense.
> Timestamp is measured in samples and this is incremented by a number of samples
> since the last packet. This way you know when to start playing the packet in
> case of DTX.
correct. How would a receiver ever know when to play back a given
packet, if there was no constantly-incrementing timestamp generated
by the transmitter sample clock. So this clock needs to continue to
coult (like a ADC sample clock), whether we currently transmit RTP codec
frames, or whether we currently suppress sending some codec frames.
So in short: sqeuence numbers will increment by one with each frame
transmitted, and timestamp will expose gaps while DTX is used.
> A proper RTP library or rather a jitter buffer should handle this
> automatically, but I'm not sure how does ortp handle it.
that's the receiving side. The transmitter will have to put correct
values in the frames, which we are not doing in osmo-bts at the moment.
--
- Harald Welte <laforge at gnumonks.org> http://laforge.gnumonks.org/
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