16 Jul
2017
16 Jul
'17
2:13 a.m.
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.
--
Len Ovens
www.ovenwerks.net