On 16.07.2017 02:13, Len Ovens wrote: > On Sat, 15 Jul 2017, Bearcat Şándor wrote: > >> Ahh, i was misunderstanding. I was under the impression that i could just >> put an >> extra 2 ethernet ports into my computer, install the kernel drivers and >> libraries >> (when they're available) and have an operational Ravenna input/output. >> However, >> if it needs a wordclock then it obviously needs a card. I had thought that >> the >> 'wordclock' was part of the data packet. > > It is not word clock. but wall clock with high accuracy so word clock can be > derived. It is possible to do an end point without by treating packets in the > same way as as buffer in an audio card where alsa does not have to be aware of > the exact clock rise or fall to deal with it. However, If you wish to send > audio > from an internal audio card to any aes67 endpoint. Your computer must be able > to > be provide an ntp server with good enough accuracy to provide wordclock to > both > your internal audio ai and to act as a master clock on the network... or be > able > to sync your internal audio card to an external ntp server. This accuracy > pretty > much requires a HW ntp server. As I said the intel i210 ethernet cards at > $60-ish seems to be about the cheapest route. > > Depending on how synced you want things... SRC can do a very good job and the > broadcast industry uses it a lot. The zita-njbridge does a great job of > connecting two computers together and I suspect using the zita src library as > part of an aes67 driver would make <whatever> ethernet card workable so long > as > the computer was never expected to be a master clock. So an aes67 network with > only two linux computers may not be usable or at least your network would not > be > wholely aes67 compliant. An endpoint with no ntp able to follow a masterclock > closely doesn't seem fully compliant to me from what I have read. So the > windows > drivers downloadable from various places would have the same problem of not > being fully compliant too. Some of the MacOS hw does have an ethernet chip > with > builtin ntp server. > > So a driver that does what the windows driver does should be possible.
It think it should be PTP [1] instead of NTP above, the latter is not accurate enough. PTP can also be run in software timestamping mode, hardware timestamping will be more accurate, though [2]. [1] https://en.wikipedia.org/wiki/Precision_Time_Protocol [2] http://linuxptp.sourceforge.net/ _______________________________________________ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
