The stream stutters or lags
Stuttering, tearing or delay on the phone. Read the stats HUD, then fix the Wi-Fi, the resolution or the GOP mode.
The picture arrives but breaks up, tears, freezes in bursts, or runs visibly behind Premiere Pro.
Almost all of this is the Wi-Fi. Turn the stats HUD on first — it tells you within ten seconds whether you are looking at a network problem or an encoder problem, and everything after that is a different fix.
1. Read the stats HUD
Open the gear in the live view, expand Developer Tools, and turn on Show stats. The panel closes itself so the numbers land on the HUD.
Five rows, top to bottom: the host machine, the source sequence, the encoder backend, what the encoder is producing right now, and the network. The Avg row below them is a rolling window you can reset, copy or expand.
The two numbers that matter are on the last row:
loss 0.3% OWD 12.4ms·Packet loss
The app colors this for you:
| Color | Value | Meaning |
|---|---|---|
| Green | 0 – 0.5% | Healthy. FEC absorbs this without a visible artifact. |
| Yellow | 0.5 – 3% | Marginal. Expect occasional blocking on motion. |
| Red | above 3% | Broken. Frames are being lost faster than FEC can rebuild them. |
Forward error correction is fixed at 10% parity, so roughly one packet in ten is redundancy. Below about 0.5% loss that redundancy is enough to rebuild every frame and you see nothing. Above it, whole frames go missing.
OWD
OWD is one-way delay, but not absolute latency — it is how far the current delay sits above the lowest delay seen in the last minute or so. It is therefore a queueing indicator, and a healthy stream sits in the low single digits of milliseconds.
The trailing character is the trend:
| Glyph | Meaning |
|---|---|
· | Steady. The path is not building a queue. |
↑ (orange) | Rising more than 12 ms per window. Something upstream is buffering — this is what a congested access point looks like. |
↓ (green) | Falling. A queue that had built up is draining. |
A steady · with red loss is interference or range. A rising ↑ with low loss
is congestion — another device is saturating the channel.
Tap the copy button on the Avg row to put the whole rolling summary on the
clipboard — 10s: loss 0.20%(max 1.10) · 48.3Mb(41.0-55.0) · 25fps · OWD 2.1ms(max 4.0, trend ↑ avg +8us). That one line is the single most useful
thing to include if you contact support.
2. Fix the Wi-Fi first
Use the 5 GHz band, not 2.4 GHz. 2.4 GHz is three non-overlapping channels shared with every microwave, Bluetooth device and neighbouring router in range. It is the single most common cause of red loss numbers. If your network publishes separate SSIDs, join the 5 GHz one on both devices.
Get closer to the access point. Wi-Fi degrades sharply through walls and floors. The phone showing three bars is not enough information — watch the loss number as you move.
Wire the computer. An Ethernet cable from the Mac or PC to the router removes half the wireless path entirely, and is usually a bigger improvement than anything you can change in the app. The phone still needs Wi-Fi on the same network.
Stop competing traffic. A cloud backup, a Dropbox sync, or someone else streaming 4K on the same access point will show up here as a rising OWD.
3. Lower the Resolution Limit
Tap the resolution chip in the HUD — the round button showing the current value, left of the gear — and step down one rung. Each rung roughly halves the pixel count and therefore the bitrate.
| Rung | Use |
|---|---|
| Source | The sequence's own frame size. Highest quality, most bandwidth. |
| 2160p / 1440p / 1080p | Cap the short side at that many pixels. |
| 720p | Marked Recommended. The default, and the right answer on a busy network. |
| 540p / 480p / 360p / 240p | Fall back further on a bad link. |
The rung caps the short side, so a 1080×1920 vertical sequence at 720p encodes at 720×1280.
On the free tier the Resolution Limit is capped at 360p on the short side and the higher rungs show a lock. See Free vs Pro.
4. Choose the right GOP mode
Open the gear and set GOP Mode under Encoding. This is the trade between bandwidth and loss tolerance, and it is the setting most worth understanding.
| Mode | HUD label | What it does |
|---|---|---|
| All-Intra | Snappy | Every frame is independent. A lost packet damages one frame and nothing after it. Costs the most bandwidth by a wide margin. |
| Short | Smooth | A short group of pictures. Middle ground. |
| Long | Long | Marked Recommended. A 600-frame group — about ten seconds at 60 fps, twenty at 30. Smallest frames, lowest bandwidth — but a lost packet can smear until the next keyframe. |
The rule of thumb:
- Loss is red and the network cannot be fixed → All-Intra. You are trading bandwidth for the guarantee that damage does not propagate.
- Loss is green but the bitrate is more than the link can carry → Long. Smaller frames mean fewer packets to lose in the first place.
The receiver also asks the plugin for a fresh keyframe when a decode fails, so a long-GOP stream does recover — it just takes until that request round-trips.
Encoder, Codec and GOP Mode are the three encoding controls; the summary line underneath restates the resulting configuration.
5. Try a different encoder engine
The Encoder dropdown at the top of the Encoding card lists the encoder backends the host machine reported. The first entry is the one the host recommends and is marked Recommended.
If the picture stutters in a way that does not track the loss number — smooth network, uneven motion — the encoder is the more likely culprit than the link. Switching from a software backend to a hardware one, or between two hardware ones, changes which chip does the work.
Switching engine rebuilds the encoder, so expect a brief interruption.
On Windows, only NVIDIA, Intel and AMD hardware encoders produce an entry in this list. A hardware encoder from any other vendor is detected but not listed, so you will see only Software (CPU) even though working hardware is present.
6. Consider the codec
H.265 is the default and produces a smaller stream at the same quality. H.264 decodes on more hardware and is more forgiving of a marginal decoder.
If the phone is a recent iPhone, leave it on H.265. Switch to H.264 if you are chasing a decode problem rather than a network one — or if you hit the 4K HEVC failure on Windows.
What the design will not do for you
PreviewMonitor does not adapt. There is no automatic bitrate controller, no retransmission and no variable FEC. The forward error correction is fixed at 10%, recovery is FEC plus a keyframe request, and every quality control — Resolution Limit, GOP Mode, Codec, Encoder — is set by hand and stays where you put it.
That is deliberate. A monitor that silently changes its own resolution is useless for judging an image, so the product would rather show you honest numbers and let you decide. It also means a bad network stays bad until you act on it — nothing is quietly compensating in the background.
The design target is a single LAN Wi-Fi hop with a 1500-byte MTU, payloads sized to 1440 bytes. Any path that is not that — a VPN, a mesh hop, a network with smaller frames — will fragment and show up here as loss.
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