On Sun, May 17, 2020 at 5:36 AM Michael Maier <m1278...@mailbox.org> wrote:
> On 17.05.20 at 01:28 Joshua C. Colp wrote: > > On Sat, May 16, 2020 at 10:58 AM Michael Maier <m1278...@mailbox.org> > wrote: > > > >> => How are the RTT values exactly calculated? Which values are actually > >> used for? > >> > > > > The value is calculated according to the logic in the RFC[1]. > Specifically > > using embedded timestamps in the RTCP packets and calculated delays. The > > value is presented in seconds I believe in the output. > > Thanks Joshua! > > >> => What about the processing time between the inbound leg and the > outbound > >> leg (transcoding, ...)? > >> > > > > That has no impact within this, since it's calculated using the RTCP > > traffic which is not used for media. It's really just for round trip time > > of a UDP packet, not for end to end time of a single audio packet/frame > > through the system. > > Let's try to sum it up on base of the given easy example how to get the > complete delay between those two speakers: > > A calls B: > ...........Receive......... > .........Transmit.......... > > BridgeId ChannelId ........ UpTime.. Codec. Count Lost Pct Jitter > Count Lost Pct Jitter RTT.... > > > =========================================================================================================== > > c8137221 327-00000004 03:22:42 g722 608K 0 0 0.000 > 608K 0 0 0.000 0.000 > c8137221 providePJSIP-xxx-0 03:22:42 alaw 608K 0 0 0.000 > 608K 0 0 0.000 0.023 > > A says something. > > 1. quantization: 20 ms > 2. processing time on the phone base / DECT: ? > 3. way from phone base to asterisk: 0 ms > 4. processing time on asterisk / transcoding: ? > 5. transport to destination: 11.5 ms > 6. processing time on destination side: ? > > Therefore it would take about 35 ms until B can here A. Is this basically > a correct estimation or did I miss(understand) something? > Roughly speaking, yes. It'd likely be more because of the aspects that aren't represented here but yes. -- Joshua C. Colp Asterisk Technical Lead Sangoma Technologies Check us out at www.sangoma.com and www.asterisk.org
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