11 Sep
2014
11 Sep
'14
10:19 p.m.
Just some cents...
On Thu, 11 Sep 2014 12:44:45 -0700 (PDT) Len Ovens <len(a)ovenwerks.net>
wrote:
Unlike MADI, empty channels would not be filled with
null data, but
rather just not sent. In MADI, 64 channels are always sent even for a
payload of 1. In this case we should send multiples of two. There is
no reason that the channel count should not change from frame to
frame, but of course the receiving sw would have to have time
(non-real time) to reset itself and audio sw that doesn't know how to
deal with more channels all the sudden might need restarting too :)
In Jack's case, if the first two were set up as the sound card, the
rest could be added as jack clients. On the AI end they would all be
jack clients anyway and jack would see the whole complement of codecs
all the time. I feel it is worth while having jack in the AI because
this would allow routing. There would be no having the outputs be
channels 9 and 10 because that happens to be how s/pdif appears
because those could look to the host like 1 and 2.
Varying channel count per packet/frame means a varying number
of malloc/free per packet -> bad for realtime. Its probably better to
stay with one channel-count once the stream is set up.
Thinking about it some more, I think one of the reasons why several
vendors use dedicated network-devices with dedicated drivers is to
reduce the need for malloc/free in the kernel/driver as much as
possible and just use fixed buffers once the channel-count (and
word-size) are known.
Have fun,
Arnold