Most AVoIP problems at commissioning trace back to the pairing decision made at tender: the wrong codec profile, a decoder undersized for the wall, or an encoder feeding more simultaneous viewers than its stream design allows. This page covers the pairing rules we apply on real projects, with the numbers behind them.
An AV over IP encoder turns an HDMI signal into a network stream. A decoder turns that stream back into HDMI. Everything that matters happens in between: how the stream is compressed, how many receivers can subscribe to it, and how much delay the whole chain adds.
HDMI in, scaled and compressed to H.264 or H.265, wrapped for IP transport. One encoder per source, regardless of how many screens show it.
Multicast on a managed switch with IGMP snooping, or unicast for point-to-point. The switch, not the endpoint, decides how far the system scales.
Stream in, decompressed and output as HDMI. Windowing, crop and rotation are applied here, which is why the decoder matters for video walls.
Routing, presets and status live in the management layer. Good designs keep this separate from the media path so a control change never interrupts a live screen.
Both units are 1GbE, Linux-based, and covered by a 3-year warranty. Firmware is ours, which is why we can change behaviour for a project rather than wait for a chipset vendor.
| Specification | QG-FBST52K — encoder | QG-FBSR52K — decoder |
|---|---|---|
| Role | HDMI → network stream | Network stream → HDMI |
| Resolution | Up to 4K@60 4:4:4 in, streamed at project profile | Up to 4K@60 4:4:4 out |
| Codec | H.264 / H.265, profile set per project | H.264 / H.265 decode |
| Network | 1GbE RJ45; fibre SFP variant on request | 1GbE RJ45; fibre SFP variant on request |
| Routing modes | Point-to-point, point-to-multipoint, many-to-many | Single source, or windowed multi-source for walls |
| KVM | USB 2.0 passthrough for keyboard, mouse, touch | USB 2.0 host emulation at the operator position |
| Audio | Embedded HDMI plus analogue in | Embedded HDMI plus analogue out, breakout on request |
| Management | Centralised from QG-1169: status, presets, firmware | Same, plus per-panel crop, rotate and bezel settings |
| Variant | QG-FBST5K (1GbE, alternative model) | QG-FBSR5K (1GbE, alternative model) |
A camera shown on twelve displays is still one encoder and one multicast group. Buying twelve encoders is the most common over-spec on AVoIP quotes. Count sources and destinations separately before pricing anything.
If a decoder must show four windows on one panel, it carries four decode sessions. Spec the wall decoder for the window count, then choose the encoder for image quality.
H.265 halves the bitrate of H.264 at similar quality, which matters on congested uplinks. H.264 has wider interoperability with third-party recorders and older decoders. Pick per project, not per catalogue.
Operator desks that both send a workstation and receive a feed need two units unless the endpoint is dual-role. FBSLTR002 / FBSLTR003 do both in one box, which halves rack space and switch ports.
Presets, firmware and status polling belong on a management VLAN. Mixing them with multicast media is how a harmless firmware push becomes a visible glitch on the wall.
Endpoint cost is small next to a site visit. A stocked spare encoder and decoder per twenty units turns a failure into a swap instead of a return-to-base.
Bitrate is a design choice, not a fixed specification. The table shows the ranges we use when sizing a network, at 1080p60 and 4K30/4K60, for typical content.
| Profile | Resolution | Typical bitrate | Streams per 1GbE port | Where it fits |
|---|---|---|---|---|
| H.264 high | 1080p60 | 8–16 Mbps | ~40–60 | Legacy interoperability, mixed estates, recording to third-party NVR. |
| H.264 high | 4K30 | 20–30 Mbps | ~20–25 | Signage and presentation where motion is limited. |
| H.265 main | 4K60 | 12–20 Mbps | ~30–40 | Default for new builds. Best balance of quality and uplink load. |
| Low-latency | 1080p60 | 20–40 Mbps | ~15–25 | KVM positions and live camera work where delay is visible. |
| Visually lossless (project) | 4K60 4:4:4 | 80–200 Mbps | ~4–8 | Radiology, colour-critical review, high-end court evidence. Needs 10GbE uplinks. |
Port counts assume a dedicated media VLAN with no other traffic. Always size the uplink for the worst-case simultaneous view, then add 30% headroom for control, recording and bursts.
Frame capture and compression, typically 15–40 ms depending on profile and GOP structure. Shorter GOPs reduce delay at the cost of bitrate.
Switching and buffering, usually under 5 ms on a well-configured LAN. Jitter buffers added by the decoder to survive congestion are the hidden cost — hence QoS.
Decompression plus display sync, 10–30 ms. Displays themselves add 10–30 ms of processing that no AVoIP vendor controls.
Practical outcomes: a camera-to-wall chain in a control room lands around 80–120 ms end to end and is invisible to the operator. A KVM desk chain needs under 80 ms to feel direct, which is why KVM endpoints should run the low-latency profile instead of the bandwidth-saving one. Ask any vendor which profile their quoted latency figure was measured on — a number without a profile is marketing.
| Room type | Encoder | Decoder | Why |
|---|---|---|---|
| Meeting room, 1–2 screens | QG-FBST52K per source | QG-FBSR52K per display | Simple any-source-any-screen with no matrix cabling; KVM optional for the room PC. |
| Courtroom | QG-FBST52K for evidence PC, document camera, remote witness | QG-FBSR52K at bench, bar table, public gallery | Independent windows per position, no re-cabling between hearings, recording from the same layer. |
| OR and clinical teaching | QG-FBST52K for endoscope, OR camera, PACS | QG-FBSR52K in lecture hall and overflow rooms | Colour fidelity and low latency matter more than bitrate here; run the low-latency profile. |
| Control room desk | Dual-role FBSLTR002/003 | Dual-role FBSLTR002/003 | Each desk sends its workstation and receives a feed in one unit; halves ports and rack space. |
| Digital signage wall | QG-FBST52K per player | QG-FBSR52K per panel group | H.265 keeps bitrate low across many panels; scheduled layouts handled by the platform. |
We will come back with an encoder/decoder pairing, the bitrate profile, the switch port plan and the latency figure for your application — within 24 hours.
The full platform: encoders, decoders, KVM, video wall control and centralised management.
How wall mapping, bezel compensation and synchronised playback are built on decoders.
The system layer: management, recording, transcoding and firmware control from one factory.
Every major platform we replace, compared at family and model level.
Eight dimensions worth comparing before a platform is specified.
Every term that appears in AVoIP quotations and commissioning documents.
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19 years of AV engineering · Shenzhen, China · 3-year warranty