Bitrate, RTT, packet loss — what do the numbers mean?
Stream health numbers explained
When you look at the Stream Health widget in the IRL tab, you'll see three main numbers: Bitrate, RTT and Packet Loss. Here we explain what each one means — and when you should be worried.
Bitrate (kbps / Mbps)
What does it measure? How much data per second you're currently sending to FizzyPeak.
- Unit: kbps (kilobits per second) or Mbps (megabits)
- 1 Mbps = 1000 kbps
Target values for IRL streams
| Quality | Bitrate target |
|---|---|
| 1080p60 (best IRL quality) | 6000–8000 kbps |
| 1080p30 | 4500–6000 kbps |
| 720p60 | 3500–4500 kbps |
| 720p30 | 2500–3500 kbps |
What do fluctuating numbers mean?
- Stable at your target value: ✅ all good
- Brief drop to 60–80 %: minor network dip, the encoder buffers. No problem.
- Drop below 50 %: warning — viewers see stutter or pixel mush
- Drop below 500 kbps: NOALBS kicks in (if active)
RTT — Round-Trip Time (ms)
What does it measure? How long a data packet takes to travel from your encoder to FizzyPeak and back.
- Unit: milliseconds (ms)
- Lower = better
Target values
| RTT | Meaning |
|---|---|
| < 50 ms | Perfect — direct fiber or strong 5G |
| 50–150 ms | Good — normal 4G/LTE |
| 150–300 ms | OK for IRL, but you'll notice the latency during chat interaction |
| > 300 ms | Problematic — high probability of packet loss |
| > 800 ms | Critical — SRT is struggling, bonding modems reconnect |
Why does RTT rise?
- Cell tower far away
- Too many devices on the same modem
- Weather conditions (rain, thunderstorms)
- Network congestion (peak times)
- Driving through a tunnel
Packet Loss (%)
What does it measure? What percentage of your packets don't arrive.
- 0 % is the goal
- SRT retransmits lost packets — but that costs extra bandwidth
Target values
| Packet Loss | Meaning |
|---|---|
| 0–1 % | Normal, SRT compensates easily |
| 1–5 % | Slightly elevated, OK with good RTT |
| 5–15 % | Warning — lower the bitrate or prioritize other modems |
| > 15 % | Critical — SRTLA bonding falls back to a single modem |
The most important equation
Stream quality ≈ Bitrate × (1 − Packet Loss) × 1 / RTT factor
A stream with 4000 kbps, 2 % loss and 80 ms RTT is better than 6000 kbps, 8 % loss and 220 ms RTT — even though the second one has a higher bitrate.
What to do with bad values?
Bitrate too low
- Check all 4G modems (the Belabox UI shows per-modem status)
- Manually reduce the bitrate to 70 %
- Raise the encoder latency (SRT latency to 4000 ms)
RTT too high
- Move closer to the cell tower
- Fewer modems in the bond (3 instead of 5 — reduces overhead)
- Check whether a modem is roaming (an expensive foreign network)
Packet loss high
- Increase SRT latency → more retransmit opportunity
- Temporarily disable a modem with high loss
- Reduce the bitrate if needed to avoid congestion
Where do I find the live numbers?
Dashboard → IRL Pro → Stream Health widget (from IRL Pro €19)
The widget shows:
- Large bitrate number (live, color-coded)
- Mini chart with the last 30 samples (≈ 90 seconds)
- Chip row: State · Uptime · Packet Loss
Chat command !bitrate
Any viewer can type !bitrate in your chat and the bot replies with the current bitrate. This is transparent and shows viewers that you're technically on top of things.
In short
- Bitrate = amount of data · higher = better quality, but needs a good connection
- RTT = latency · lower = better
- Packet Loss = % of lost packets · 0 % is ideal, up to 5 % is OK
All three numbers together tell you whether your stream is currently stable. In the IRL tab you can see them live.
Noch Fragen? Öffne das Dashboard oder schreib im Discord #support.