These will likely "listen" to your microphone whenever you have a virtual machine running, even if that virtual machine doesn't seem to be using the microphone at the moment. Virtualization software such as VMware, VirtualBox, or Parallels.Any VoIP application such as Skype or FaceTime.These applications could be running in the background while using your microphone. Boom by Global Delight Technologies ( reference)-as far as I can tell, this shouldn't be using the microphone.HipChat after first time camera/mic are used, such as when opening preferences (see HipChat forums).They do not release their hold on the microphone properly. These applications need to be restarted in order to restore normal CPU usage. The problem goes away a minute or two after the problem applications are closed. Various other ways of measuring the latency exist, but the above mentioned is a simple way of getting a measurement that is precise enough to know if your audio delay is really 60 ms larger than your visual delay.Certain applications appear to be triggering this problem when interacting with the microphone. Then make the program trigger the output (could be a digital I/O or in simple terms showing something on the screen) - and then measure the amount of time before you see the audio in the signal (on the oscilloscope or in the audio track of the video recording). In simpler terms, you could use an iPhone with slo-mo video recording. If you have the equipment, you could use for example an oscilloscope with a trigger input. Therefore using it to measure response times in units of milliseconds is not going to be precise at all.Ī way of measuring it would be to use an audio recorder of some sort with known low latency combined with another type of output from the computer with known low-latency. this command in itself could take a (relatively) long while to actually play the audio. It's much more accurate because it removes the overhead of the CPU management and gives you a truly accurate elapsed time.įirst off - using echo -ne '\007' to play audio is not "low-latency" audio. This is why you need a device called an Audiometer that is a purpose built piece of hardware that measures the time between the two events - sound and keypress. If we subtract the top values from the bottom, we can get pretty close to how much time elapsed. When you hear the beep, press Enter!įrom this one, we can see that there was some overhead that caused the process to account for more time. The resolution of the time utility is not granular enough to measure the time elapsed to execute each command so we assume it happened "immediately." 812s difference between when I heard the beep and pressed Enter. In the above example it shows that the latency according to the computers "stopwatch", there was a. Sample Output: When you hear the beep, press Enter! So, in order of accuracy, Real is in the ballpark, User is pretty darn close, and Sys is dead on balls accurate, as far as the CPU is concerned. Sys - this is the time spent inside the kernel and is also the actual time spent by the CPU.įor more information on this see Real, User and Sys process time statistics.User - this is the time spent in the user space outside the kernel and is the actual CPU time spent executing the task.This accounts for all processes running at the time. Real - the time start to finish of the call measured if you had a stopwatch in hand.# generate a random number between 3 and 10 for seconds to wait for beepĮcho "When you hear the beep, press Enter!" I've created a basic bash script that will prompt the user to press Enter after waiting for a beep to occur after a random period. However, you can get fairly close in bash by using the time function. ![]() To be "more accurate" you'd need to write a program that could directly access the kernel so that you could evaluate the actual time between events - the beep and the keypress. You really cannot measure the latency "through" the OS because of the overhead of queuing and managing the processes.
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