webrtc - Why solutions like pusher claim to be "Real time"? -


i have been using pusher time now. assumed "real time" meant "instantaneous". lately have step article: https://en.wikipedia.org/wiki/real-time_computing, , sentence grab attention:

"real-time programs must guarantee response within specified time constraints"

they give example based on audio processing:

"consider audio dsp example; if process requires 2.01 seconds analyze, synthesize, or process 2.00 seconds of sound, not real-time. however, if takes 1.99 seconds, or can made real-time dsp process."

my questions: 1. definition applies hardware/electronic devices or can applied software too? 2. if applies software, apply remote services pusher? 3. time constraint pusher considered "real time"? 4. time constraint other services webrtc, firebase?

sorry lengthly post doesn't answer question, hope make better undestand "real time" definition comes from.

yes, understandable confusion "real time" means "instantaneous". if start think find out "instantaneous" difficult define.

what instantaneous mean? 0 (zero) seconds response time (as in 0 sec 0 ms 0 ns 0 ps) time of command time of response physically impossible. can try instantaneous mean command-response time perceived instantaneously, i.e. not seen delay. then... "perceived instantaneously" mean? perceived humans? ok, good, getting somewhere. human eye , brain image processing very complex machine , not work in fps, can use data approximate some. human eye can "perceive image flashed on screen 1/250th of second". 0.004 seconds or 250 fps. approximation graphical program real time if has response time < 0.004 sec or run faster @250 fps. know in practice games perceived smooth people @ 60 fps, or 0.01666 seconds. have 2 different answers. can somehow justify them both? yes. can in theory realtime mean 0.004 seconds, in practice 0.01666 seconds enough.

we happy , stop here, on journey of discovery. lets think further. want "real time" avionic automation system have 0.01666 seconds response time? deem acceptable 0.01666 seconds response time "real time" nuclear plant system? oil control system valve takes physically 15 seconds close defined "real time" if command-completion time 0.0166 seconds? answer these questions no. why? answer , answer why "real time" defined is: "real-time programs must guarantee response within specified time constraints".

i sorry, not familiar @ "pusher", can answer first question , part of second one: "real times" can applied system needs "react" or respond form of input. here "system" more generic might think. brain qualify, in context of engineering means whole stack: hardware + software.


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