[Jack-Devel] Suggestion for two new tools
me at jmendeth.com
Sun Jun 19 19:29:55 CEST 2016
I'd like to suggest two new tools. I find myself using them frequently
whenever I'm dealing with sets of outputs / inputs of different
latencies, or sometimes when I'm using software that adds noticeable
(i.e. >= 15ms) latency.
I think it would be best to add them as standard JACK tools because:
- They perform a very basic task.
- JACK has almost no latency-related tools AFAIK.
- They demonstrate the power of JACK's latency API and could serve
as [non-trivial] examples for devs trying to understand it.
What do you think? I've attached a patch with both tools. If they get
included, I'll write documentation about its usage and the latency API
in general. Below is a summary of what they do:
Synchronizes a set of ports for playback or capture, by inserting
appropriate delays to compensate for latency. Example:
Suppose you have one output `playback_1` with 20ms output latency, and
another output `playback_2` with 50ms output latency:
jack_lsync -a2 &
jack_connect lsync:output_1 playback_1
jack_connect lsync:output_2 playback_2
lsync will insert a 30ms delay on the first output, giving you two
outputs of 50ms latency. Instead of connecting to the original outputs,
you'd connect to `lsync:input_1` and `lsync:input_2` respectively.
Corrects the reported latency of a port. Example: to increment the
playback latency of `port` by 30ms:
jack_lset 30ms &
jack_connect lset:output_1 port
Then connect everything to `lset:input_1` instead of `port`.
Clients should ideally set the correct latency at their ports, or
provide an option (as with -I and -O) for users to set them. This is not
the case in practice, and there are also a number of legitimate reasons
why users may want to correct latency externally.
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