Re: [Jack-Devel] I'm confused about latency

On 4/5/19 11:27 AM, Alexandre BIQUE wrote: No, it should propagate latencies. But in this simple case it's not relevant at all. A better example is [HW Input] -> [App1] -> [App2] -> [HW Output] Each App is interested in two things: - how long has it been since the data read from a port arrived at the edge of the graph (capture, from hw-input) - how long will it be until the data written to a given port will arrive at the edge of the graph (playback, to hw-output) App1 should read the HW input *capture*-latency from its input port, add its own latency and inform App2 about the sum by setting the capture latency of App1's output port. Likewise, App2 should add its latency to the *playback* latency of its output port and forward that to App1 by setting the playback latency of App2's input port. Please see http://jackaudio.org/api/group__LatencyFunctions.html#ga7a8f181fcec32945db7… That outlines above algorithm One example use-case is Overdubs: e.g. App1 plays back, App2 adds some latent effect (e.g. a Limiter). A musician listens to HW output, sings along into the HW-input and App1 records it. The recording should be in sync with the playack. Yes, the port latencies, which may or may not be related to hardware. -=- As for absolute alignment, that's jack-transport or jack-time, which provides a clock based on the soundcard's oscillator. -- unrelated to the operating-system's time. http://jackaudio.org/api/group__TimeFunctions.html Hope that helps, robin