Creative Broadcast Agency

Venue testing

Jitter test for live streaming: what jitter is and how we check a venue.

A jitter test measures how much the delay on a connection varies from moment to moment. A stream can live with a steady delay. It struggles with a delay that keeps changing, because every buffer has to be sized for the worst moment. This is what jitter does to live video, the thresholds StreamCertified uses, and how we check a venue for it.

Reading time
4 min read
Updated
Updated
Run the free jitter test
Jitter for Ready
< 15 ms
Not ready from here
30 ms
Latency for Ready
<= 80 ms
Round trips per test
40
The short answer

What does a jitter test measure?

A jitter test measures jitter: how much the delay on a network connection varies from one moment to the next. If every packet takes 40 ms, the delay is steady and jitter is low. If packets take 20 ms, then 90 ms, then 35 ms, jitter is high.

A live stream can cope with a steady delay. It struggles when the delay keeps changing, because the encoder, the transport and the player all have to buffer for the worst moment. Too little buffer and the picture stutters. Too much and the stream falls further behind the room.

We check jitter on every venue with the StreamCertified jitter test.

Run the free jitter test on StreamCertified

Jitter vs latency

Jitter and latency are not the same thing

Technical specification
LatencyJitter
What it isHow long a packet takes to arriveHow much that time varies
What the viewer seesThe stream runs behind the roomStutter, buffering, audio drift
Can a buffer absorb it?It does not need to; the delay is fixedOnly by adding delay
Ready (StreamCertified)80 ms or less to the test serverUnder 15 ms

A satellite link can have high latency and low jitter, and carry a clean stream. A busy venue Wi-Fi can have low latency and high jitter, and break one.

Why it matters

Why jitter matters for live video

Live video is a steady flow of frames. The network delivers them unevenly. Buffers smooth that out, and every buffer adds delay.

  • SRT holds packets for a set latency window so it can re-order them and re-send lost ones. If jitter is larger than that window, late packets count as lost. See SRT.
  • Players buffer a few seconds of video. High jitter drains the buffer and the viewer sees a spinning wheel.
  • Interactive paths, such as remote speakers and interpreters, need a small buffer to keep conversation natural. They feel jitter first.

So jitter decides how much delay you must accept to keep the picture clean. For low latency streaming, jitter is often the real limit.

Thresholds

How much jitter is too much

Technical specification

These are the thresholds StreamCertified uses. Jitter is graded strictly under each figure.

JitterVerdictWhat we do
Under 15 msReadyStandard settings.
15 ms to under 30 msCheckLarger transport buffer, wired port, re-test under load.
30 ms or moreNot readyNot the show path on its own. Fix the network or add a second path.

Latency to the test server is graded alongside it: 80 ms or less is ready, up to 150 ms needs checking. That round trip is to the server named on the result, not to your internet provider.

What the test measures

How the jitter test measures it

The tool times 40 round trips to its test server, with a 3-second timeout on each. Jitter is the standard deviation of those round trips. Latency is the fastest one, which is the path with queueing noise stripped out. The result also shows the average, the slowest trip, how many requests did not answer, and a second jitter figure based on the difference between consecutive trips.

It measures round-trip jitter over HTTP, not the jitter of a media stream itself. That makes it a fast, fair read of the network before any kit is set up. On show day, SRT's own statistics give us the media-path picture.

How we do it

How we check a venue for jitter

  1. Wired and Wi-Fi, side by side. Wi-Fi jitter climbs with the crowd. The wired port is usually far steadier. The comparison makes the case to venue IT.
  2. Look at the slowest trip. The average hides spikes. One 400 ms round trip in forty is the moment a stream stutters.
  3. Test when the room is full. Registration, coffee breaks and the moment everyone opens a phone are when jitter peaks.
  4. Set the buffer from the reading. We size the SRT latency window from the measured round trip and its variation, not from a default.

Jitter is one line of our full venue readiness check, alongside upload and packet loss.

The second path

What we change when jitter is high

We move the encoder off Wi-Fi. We ask for a dedicated line or VLAN, with traffic priority if the venue supports it. We raise the transport buffer and accept a little more delay for a clean picture. And we add a second path, bonded 5G, so if the venue network turns unstable the stream carries on and a failure never reaches your audience.

This is standard on our live streaming in Dubai shows.

Run the free jitter test on StreamCertified

If the result worries you, send us the venue and we will test it first.

FAQ

Questions we get asked.

What is a good jitter for live streaming?

Is jitter worse than latency for a live stream?

Why is jitter so high on venue Wi-Fi?

Can SRT handle jitter?

Tell us the date, the venue and who is watching.

We scope every engagement against its run of show, not a package.

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