Javascript Web Audio API latency

Question

I want to make a Javascript program to process some audio from microphone. But when I make just a basic example, like get audio from microphone and play it back without any processing, just like this

source = audioCtx.createMediaStreamSource(stream);
source.connect(audioCtx.destination);

I get 200 milliseconds latency between input and output audio. I tried in Google Chrome and Firefox on 2 different PCs with Windows 7 and Windows 10 and it looks the same everywhere. I got this number (200ms) by recording and analysing audio with an external device, not just by my ears.

In official W3C specification here they tell about 3-50 ms latency. 30-50 ms is what I need. I do not really need 3-5 ms.

I tried to play with latency parameter like this

navigator.mediaDevices.getUserMedia({
  audio: {
    latency: 0.05,
    echoCancellation: false,
    mozNoiseSuppression: true,
    mozAutoGainControl: false
  }
});

but looks like it is ignored by Chrome and FireFox.

My full example is available here.

https://jsfiddle.net/xfq3ykp7/71/

Is it browser/hardware limitation or I am doing something wrong? Can anyone hear some latency with my example? Usually, it is easy to check it with hitting a table near a microphone. for 200 ms there is a noticeable delay between the hit and its sound.

I do not need complicated things like scheduled audio events etc which are needed for games or online musical instruments. I just need to decrease latency in my simple example from 200 ms to 50 ms or ideally to 20 ms.

UPDATE1:

I could make 70 ms on Windows 10 and 100 ms on Windows 7 in Firefox with that code change

var p = navigator.mediaDevices.getUserMedia({
  audio: {
    latency: 0.02,
    echoCancellation: false,
    mozNoiseSuppression: false,
    mozAutoGainControl: false
  }
});

Thanks to firefox support (https://bugzilla.mozilla.org/show_bug.cgi?id=1375466). But they tell that 30 ms should be possible. The question is still open "How to get 30 ms latency on Windows?" and "What is hardware requirements?".

Answer 1

I know that this is a very old question, but the problem remains (8 years later, in 2025), at least in Firefox on Linux. I therefore did the following test with Python, i.e., avoiding the browser and the web audio API altogether:

import pyaudio
pa = pyaudio.PyAudio()
stream_in = pa.open(format=pyaudio.paInt16, channels=1, rate=44100, input=True, frames_per_buffer=512)
stream_out = pa.open(format=pyaudio.paInt16, channels=1, rate=44100, output=True)
while True:
    stream_out.write(stream_in.read(512))

The latency seems to be pretty much the same as with direct playback in the browser. I conclude that the problem is likely caused by the OS and/or its drivers, not by the browser and the web audio implementation.