[Jack-Devel] I'm confused about latency

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Re: I'm confused about latency

Alexandre Bique
On 4/6/19 2:30 PM, Robin Gareus wrote:
>> To sum up in one sentence, in my opinion it is better to not have
>> latency compensation than having it working half of the time.
> A user asking for ambiguous latency situations is not an design issue
> with JACK. The 'range' was specifically added to account for this and
> allow jack-clients to cope with it.

So I did not understand how to cope with the latency range. Please could
explain it to me (again?)?

I would be really interested to read the fix of Ableton Link's LinkHut
with jack backend regarding latency compensation.

Thank you,
Alex
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Re: I'm confused about latency

Robin Gareus
On 4/6/19 2:53 PM, Alexandre BIQUE wrote:

> I would be really interested to read the fix of Ableton Link's LinkHut
> with jack backend regarding latency compensation.
>

LinkHut only has playback/output ports and transmits time, right?

If so, simply query the output port's latency-range and use the max.
Then offset the timestamp to transmit by the output's latency  (send
future time so that by the time it arrives on the physical outputs a bit
later it's valid).

You may want to subscribe to jack's graph-order callback and update the
alignment when connections change..

HTH,
robin
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Re: I'm confused about latency

John Rigg
In reply to this post by Alexandre Bique
On Fri, Apr 05, 2019 at 10:36:02AM +0200, Alexandre BIQUE wrote:
>  - the driver should have a rough idea of how much hardware latency is
> introduced by the audio interface

The driver has no way of knowing the latency of the ADC and DAC
circuitry. That has to be measured.

(As an example, think of a PCI(e) MADI or ADAT card which can be
used with a variety of different external DACs or ADCs).

John
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