[Ardour-Users] Delta1010 + Edirol FA-101
arnold at arnoldarts.de
Mon Jul 9 15:35:13 PDT 2012
On Monday 09 July 2012 08:14:37 Ben Bell wrote:
> Returning to FFADO -- if I had a pair of identical devices, is there
> anything reason to expect that their latencies will be the same. Despite the
> clock sync preventing drift, is they are still necessarily going to be
> delivering their packets to the host server at different times, and perhaps
> split at different points in the stream. Is this too small a thing to
> notice or is there some need for compensation there too?
The killer-feature of firewire is that the data-streams are synced. So that
means that the data from the two devices always comes in at the same time (or
with a constant delay) and ffado unpacks it all into one synced data-stream for
Actually with firewire you get three possible clocks for syncing devices:
ADAT/SPDIF/Wordclock of the devices, the isochronous streams themselves and
the firewire clock driving the streams but also delivered additionally. Of
course the first depends on what the devices actually have and sadly not all
devices implement syncing to both the firewire timebases.
> Perhaps it would be fine for two different instruments but not wise to split
> a stereo channel between two devices.
Also keep the whole drums on one device.
One problem only recently fixed (I believe) is that the time-shift between
devices is random on each stream-initialization, thus can be different in
different recording-sessions. But once you record a loud shot on all the
channels, you can measure how much to nudge these ardour-tracks.
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