[Jack-Devel] Suggestion for two new tools

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: ## jack_lsync 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. ## jack_lset 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.