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Re: what is acceptible jitter for voip and videoconferencing?


From: Michael Thomas <mike () mtcc com>
Date: Thu, 21 Sep 2023 17:04:12 -0700


On 9/21/23 3:31 PM, William Herrin wrote:
On Thu, Sep 21, 2023 at 6:28 AM Tom Beecher <beecher () beecher cc> wrote:
My understanding has always been that 30ms was set based on human perceptibility. 30ms was the average point at which 
the average person could start to detect artifacts in the audio.
Hi Tom,

Jitter doesn't necessarily cause artifacts in the audio. Modern
applications implement what's called a "jitter buffer." As the name
implies, the buffer collects and delays audio for a brief time before
playing it for the user. This allows time for the packets which have
been delayed a little longer (jitter) to catch up with the earlier
ones before they have to be played for the user. Smart implementations
can adjust the size of the jitter buffer to match the observed
variation in delay so that sound quality remains the same regardless
of jitter.

Indeed, on Zoom I barely noticed audio artifacts for a friend who was
experiencing 800ms jitter. Yes, really, 800ms. We had to quit our
gaming session because it caused his character actions to be utterly
spastic, but his audio came through okay.

When I wrote my first implementation of telnet ages ago, i was both amused and annoyed about the go-ahead option. Obviously patterned after audio meat-space protocols, but I was never convinced it wasn't a solution in search of a problem. I wonder if CDMA was really an outgrowth of those protocols?

But it's my impression that gaming is by far more affected by latency and thus jitter buffers for voice. Don't some ISP's even cater to gamers about latency?

Mike


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