Optimizing for Sync

FloSync is designed to keep your screens in sync automatically. For most setups, it works great right out of the box. But if you're building a video wall, running a professional installation, or simply want the tightest possible synchronization, the choices you make about your network, hardware, video files, and system settings all add up.

This guide walks you through each factor and helps you build a setup that delivers rock-solid sync.

What Great Sync Looks Like #

Before diving in, it helps to set realistic expectations.

Human perception: In real installations, the goal is visual alignment that looks seamless to your audience.

What FloSync targets: After clients connect, FloSync stabilizes quickly and keeps playback aligned during long sessions.

The goal isn't a lab number, it's imperceptible sync in your venue. Every recommendation in this guide helps remove sources of inconsistency so FloSync can stay smooth and stable.

Bottom line: Good networking, optimized video files, and clean system setup produce the most reliable results.

Network Configuration #

Your network is the foundation. FloSync computers communicate over UDP on your local network, and the quality of that connection directly affects sync stability.

Wired vs. WiFi #

For video walls and sync-critical installs, wired Ethernet is strongly recommended. WiFi can introduce variability that is harder to control.

For distributed setups, like individual TVs around a retail store showing the same promotional video, WiFi works fine. When screens aren't viewed side by side, small timing differences are invisible to viewers and FloSync keeps everything close enough that nobody will notice. If WiFi makes your installation easier, use it.

Keep It Simple #

The fewer network hops between your computers, the better:

• Best: All FloSync computers plugged into the same network switch
• Good: Same subnet, connected through one or two switches
• Avoid: Connections that cross routers, VLANs, or subnets

A basic unmanaged gigabit switch is all you need. Fancy managed switches work fine too, just make sure nothing is filtering or throttling UDP traffic on port 9201.

Dedicated Network (Optional but Ideal) #

For the most demanding installations, consider a dedicated network just for FloSync:

• Use a separate switch that only your FloSync computers are connected to
• No other traffic competing for bandwidth
• No risk of network congestion from other devices
• Each computer can also have a second network connection for internet access if needed

This isn't necessary for most setups, but it eliminates network variability entirely.

For a complete step-by-step guide to building an isolated network with no internet connection — including OS lockdown to prevent background updates, cloud sync, and other interference — see Dedicated Network Setup.

Firewall and Port Requirements #

FloSync uses UDP port 9201 for sync communication. Make sure:

• Firewalls on all computers allow FloSync (or UDP port 9201)
• No network-level firewalls or filters are blocking UDP between your machines
• If you're on a corporate network, ask your IT team to allow UDP 9201 on the local subnet

See Network Sync - Firewall Configuration for platform-specific instructions.

Video Encoding Choices #

Your video format has a direct impact on sync consistency, and it's one of the easiest things to improve.

Why Encoding Matters for Sync #

FloSync keeps computers aligned automatically during playback. Sync-friendly video formats make this process smoother and more consistent.

Standard delivery formats from cameras, editors, and the web are great for file size. For sync-critical installations, dedicated production formats are usually more consistent across machines.

Sync-friendly formats generally provide steadier long-run behavior, especially in multi-computer video walls.

What We Recommend #

Use ProRes LT on macOS and DNxHD on Windows. If storage is limited, H.264 All-Intra is a good alternative with smaller file sizes.

Test Before You Transcode #

You may not need to re-encode your content at all. We provide downloadable sample videos in various formats so you can compare sync performance on your own hardware before committing to a format.

When you're ready to convert, FloSync's built-in Transcode Panel makes it easy — pick a format, queue your files, and let it run. No external tools needed.

For format comparisons, sample file downloads, and manual FFmpeg commands, see the Video Preparation guide.

Match Files Across Computers #

When using network sync, every computer should have an identical copy of the same video file:

• Don't mix formats (for example, ProRes on one machine and H.264 on another)
• Copy files to each computer's local storage rather than playing from a network share
• Even if the visual content is the same, differences in encoding can cause drift

Looping Mode #

If your content loops continuously (as most signage and video wall content does), your choice of looping mode significantly affects sync quality over time.

Standard Looping #

In standard mode, the video player reloads the file each time it reaches the end. This creates a brief transition at the loop point. During that transition, computers may momentarily fall out of sync, requiring FloSync to correct.

Over a long session, these corrections add up. Your system stays in sync, but it's doing more work to get there.

Seamless Looping #

Seamless mode eliminates the loop transition entirely. FloSync prepares your video for continuous playback when you Go Live.

In many setups, seamless looping noticeably reduces correction events and produces steadier long-run playback.

Our Recommendation #

Use Seamless looping for any installation where sync quality is the priority. It's the default for a reason.

You can change the looping mode in Preferences.

Hardware and GPU #

Use Similar Hardware Across Computers #

When multiple computers need to stay in sync, consistency matters. Differences in GPU, CPU, or storage performance can affect how evenly systems run over time.

For the tightest sync:

• Use the same model of computer for all nodes when possible
• At minimum, use the same GPU generation across machines
• Ensure all machines have SSD storage (not spinning hard drives)

GPU and Video Decoding #

Modern GPUs handle video decoding in hardware, which is both faster and more consistent than software decoding. FloSync uses hardware-accelerated decoding automatically when available.

For best results:

• Use a dedicated GPU (not integrated graphics) for 4K content
• Keep GPU drivers up to date
• Avoid running GPU-intensive applications alongside FloSync
• If using multiple screens per computer, make sure your GPU supports the total pixel output

Storage Speed #

High-bitrate formats like ProRes and DNxHR need fast storage:

• SSD (internal or USB 3.0+): Recommended for all formats
• NVMe SSD: Ideal for 4K ProRes/DNxHR
• USB 2.0 or spinning hard drives: May not keep up with high-bitrate content
• Network drives: Not recommended, always use local storage

System Configuration #

Small system-level details can make a surprising difference for long-running installations.

Disable Sleep and Power Saving #

A computer that goes to sleep or throttles performance will break sync.

Windows:

• Settings > System > Power > set to High Performance or Best Performance
• Disable screen timeout and sleep under power settings
• Disable USB selective suspend (can cause display adapter issues)

macOS:

• System Settings > Displays > Advanced > Prevent automatic sleeping
• System Settings > Lock Screen > set screen saver and display sleep to Never (or a very long interval)
• Consider using caffeinate in Terminal for kiosk setups

Disable Automatic Updates #

Nothing disrupts an installation faster than an unexpected restart.

Windows:

• Pause Windows Update during your event or installation period
• Disable automatic driver updates if possible
• Set active hours to cover your operating window

macOS:

• System Settings > General > Software Update > disable automatic updates during your installation

Close Unnecessary Applications #

Every application competing for CPU, GPU, and memory takes resources away from video playback:

• Close web browsers, email clients, and chat applications
• Disable startup applications you don't need
• On Windows, minimize background services where possible
• Disable notifications to prevent pop-ups from appearing over fullscreen content

Screen Saver and Lock Screen #

Make sure the computer doesn't lock or show a screen saver during playback:

• Disable screen saver entirely
• Disable lock screen / password requirement after sleep
• FloSync enables a wakelock during Go Live to prevent sleep, but screen saver settings are separate

Schedule Regular Restarts (Long-Running Installations) #

If your installation runs unattended for days or weeks at a time, schedule a daily restart on every computer — for example, at 2:00 AM or whenever your venue is closed.

Why this matters: FloSync synchronizes computers by comparing their system clocks. Every computer's clock is driven by a hardware oscillator — a tiny crystal that vibrates at a precise frequency. Over days of continuous operation, heat from the CPU, GPU, and other components causes these oscillators to drift at slightly different rates on each machine. Your operating system's time service (NTP) periodically corrects the clock, but these corrections can be abrupt rather than gradual, and they happen independently on each computer. The result is that after several days of uptime, the clocks on two machines may be drifting in ways that are difficult for any software to fully compensate for in real time.

A restart resets this accumulated state: the OS performs a fresh time sync, hardware temperatures normalize briefly, and video decode pipelines start clean. It's the same reason professional digital signage systems, broadcast playout servers, and AV installations routinely schedule overnight restarts — it's an industry best practice, not a workaround.

FloSync is designed for this. With Launch at Login and Auto Go Live enabled, your installation recovers automatically after a restart — FloSync launches, reconnects to the network, and goes live without any manual intervention. The entire restart cycle is invisible to your audience.

How to schedule restarts:

Windows:

• Open Task Scheduler and create a new task
• Set the trigger to Daily at your preferred time (e.g. 2:00 AM)
• Set the action to run shutdown /r /t 0

macOS:

• System Settings > General > Startup & Shutdown > set a schedule (older macOS: Energy Saver > Schedule)
• Or use sudo pmset repeat restart MTWRFSU 02:00:00 in Terminal

The Optimization Checklist #

Use this as a reference when setting up a sync-critical installation.

Network #

• [ ] All computers connected via wired Ethernet
• [ ] All computers on the same subnet
• [ ] Ideally connected to the same switch
• [ ] Firewall allows FloSync / UDP port 9201
• [ ] No network filters blocking UDP between machines

Video Files #

• [ ] Videos encoded in a sync-optimized format (use the Transcode Panel or see Video Preparation)
• [ ] Identical files copied to each computer's local storage
• [ ] Files stored on SSD (not network drive or USB 2.0)
• [ ] Tested playback on each machine individually before going live

Software Settings #

• [ ] Seamless looping enabled in Preferences (if content loops)
• [ ] Server/client network sync configured and connected
• [ ] Global Canvas Extension configured on each computer (for video walls)
• [ ] Default sync tolerance settings (adjust only if needed)

System #

• [ ] Power plan set to High Performance (Windows) or sleep disabled (macOS)
• [ ] Automatic updates paused or disabled
• [ ] Screen saver and lock screen disabled
• [ ] Unnecessary applications closed
• [ ] GPU drivers up to date
• [ ] Daily restart scheduled for unattended installations (with Launch at Login and Auto Go Live enabled)

Before Going Live #

• [ ] Start the server first, then connect clients
• [ ] Allow initial sync to settle before evaluation
• [ ] Watch status indicators and confirm playback remains stable
• [ ] Run a test session before your event or opening

Still Seeing Issues? #

If you've followed this guide and are still experiencing sync problems:

1. Check the Troubleshooting guide for specific symptoms and solutions
2. Review the Diagnostic Logs, which record sync events and can help pinpoint the cause
3. Try our sample video files to rule out encoding issues
4. Contact us with your log files and we'll help diagnose your setup

Related #

• Network Sync: Setting up server/client sync
• Video Preparation: Encoding formats and sample files
• Transcoding: Convert videos to sync-optimized formats in FloSync
• Preferences: Sync tolerance and looping mode settings
• Troubleshooting: Common issues and solutions