Hardware, software, latency, clerking, and post-sale reconciliation for a live simulcast auction — operator's how-to.
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A live simulcast auction broadcasts your in-room sale to remote bidders in real time over the web and mobile, accepting their bids alongside floor, phone, and absentee bids and clerking everything into a single ledger. To run one well you need three video feeds (auctioneer, lot, room), an audio mix with a wireless lavalier on the auctioneer, an encoder pushing sub-second-latency video to the bidder console, an auctioneer/clerk console synchronised with the platform, and a tested fallback for every link in the chain. Latency under 450ms keeps remote bidders psychologically present in the room; over 1.5 seconds and they fall behind the floor and bidding collapses.
Simulcast is now the default format for any auction house running sales above six figures. Christie's reports 80% of bids in 2025 came from online channels. The operational complexity is real: you are running a live broadcast, a real-time betting platform, and a high-stakes commerce transaction simultaneously, and any failure on any of those three is visible to every bidder. This is an operator's how-to covering the hardware, software stack, latency budget, common failure modes, and post-sale reconciliation.
What "simulcast" actually means
A simulcast auction is a live in-room sale where the auctioneer's call is broadcast in real time to remote bidders, who can place bids from a web or mobile interface and have those bids clerked into the same ledger as floor, phone, and absentee bids. The auctioneer sees online bids on a console at the rostrum. Whoever has the highest active bid at the moment the hammer falls — floor, phone, online, or absentee — wins.
Two adjacent formats often confused with simulcast:
Timed online auction — no live auctioneer. Lots have a scheduled close time and bidding extends with anti-snipe rules. Asynchronous.
Webcast-only auction — broadcast and online bidding but no in-room floor. Auctioneer sells to the camera. Simpler than simulcast because there is no floor to coordinate.
A true simulcast has all four bid channels live at once. See our glossary entries on simulcast and live auction for the broader definitional context.
The hardware setup
Simulcast hardware splits into video, audio, network, and rostrum.
Video
A credible simulcast feed needs three camera angles minimum:
Auctioneer camera — wide-angle headshot of the auctioneer at the rostrum. This is the camera bidders watch most of the time. Use a 4K-capable camera with autofocus locked to the rostrum spot. Sony FX3, Canon C70, or equivalent broadcast-grade.
Lot camera — static or PTZ camera on the lot display. Operator-controlled zoom for fine detail. For jewelry and watches, a macro-capable lens is essential.
Room/wide camera — establishing shot of the floor showing paddles being raised. Less critical but adds production value and bidder confidence that the room is real.
Mid-market houses often add a fourth camera for VIP or back-of-room coverage. Top-tier houses (Christie's, Sotheby's) run 6–8 cameras with a vision mixer.
Audio
Audio failure is the most common simulcast failure. Online bidders abandon a broken video feed within 60 seconds and a broken audio feed within 30 seconds — voice is what tells them the auction is still alive.
Auctioneer microphone — wireless lavalier (Sennheiser EW or equivalent) plus a hardwired backup. Use both, not either-or. Rostrum lighting and movement can disrupt wireless; the cable backup catches the dropout.
Room microphone — overhead boundary mic to capture floor bid acknowledgment ("yes!", "back to you, sir"). Bidders draw confidence from hearing the room engaged.
Audio mix — dedicated mixer (Behringer X32, Yamaha QL5, or equivalent) consolidating mics into a clean broadcast feed. Auctioneer voice should be 70–80% of the mix; room ambient 20–30%.
Network and encoder
This is where most operations underspend. The encoder converts your video feeds and audio into a streaming format and pushes it to the bidder console.
Hardware encoder preferred over software (LiveU LU800, Teradek Prism, or equivalent). Hardware is purpose-built for low-latency reliability.
Bonded internet — at minimum two independent internet uplinks (different ISPs, ideally fiber + 4G/5G cellular). The encoder fails over automatically. Single-uplink simulcast is a reputational risk.
Bandwidth budget — at least 25 Mbps upstream sustained for a 1080p broadcast plus rostrum console traffic. Plan for 50 Mbps if running 4K.
Latency-optimized streaming protocol — WebRTC or low-latency HLS. Standard HLS adds 6–30 seconds; that is unusable for live bidding.
Rostrum console
The auctioneer needs a screen at the rostrum showing:
Current high bid (any channel)
Current high bid channel (floor / phone / online / absentee)
Online bidders watching the lot (count + recent activity)
Time on lot
Reserve status indicator (private — only auctioneer sees the figure)
Next bid increment
Active phone bidders standing by
Auction Rabbit's auctioneer console is built for sub-450ms round-trip — auctioneer call to online bid back at the rostrum — which is the threshold below which online bidders feel like they are bidding against the floor in real time. Above ~1.5 seconds round-trip, online bidders fall behind and the floor wins everything; sell-through online drops sharply.
Clerk station
A clerk sits at a separate station running the catalogue, clerking each lot's hammer into the system, recording paddle numbers and final prices, and confirming consignor reserves are met. The clerk console mirrors the auctioneer's console with full edit rights to lot status.
The software stack
The minimum stack is:
Layer
Function
Examples
Auctioneer console
Rostrum display + control
Auction Rabbit, ATG Live, Bidpath Auctioneer
Bidder web/mobile
Where remote bidders watch and bid
Auction Rabbit Web + Mobile, HiBid, LiveAuctioneers, Invaluable
Livestream encoder
Video/audio ingest and broadcast
LiveU, Teradek, OBS (software fallback)
Clerk software
Lot-by-lot ledger
Auction Rabbit Clerk, Auction Flex
Payment processing
Post-hammer settlement
Stripe, Adyen, internal merchant
Identity/KYC
Bidder verification
Onfido, Sumsub, in-house KYC
Auction Rabbit unifies the auctioneer, clerk, bidder, and broadcast layers into one platform — see the Web product, Mobile bidder, and AI hammer-prediction features. Mixed-vendor stacks introduce sync and reconciliation gaps; integrated stacks shrink that risk.
Pre-sale tech rehearsal
The single most important operational habit in simulcast is the pre-sale rehearsal. Run a full end-to-end test 24–72 hours before the sale. Common rehearsal protocol:
Camera and audio check — all feeds live, all mic levels correct, lot camera focused at the lot table distance. Rehearse the auctioneer movement that occasionally hits the wireless mic dropout.
Encoder + network check — confirm both uplinks active, simulate a primary-link failure, confirm failover is seamless on the broadcast.
Auctioneer console end-to-end — place a test online bid from a remote device, confirm it appears on the rostrum within the latency budget, confirm clerk can record the hammer, confirm the test transaction reverses cleanly.
Phone-bid integration — phone-clerks call in a test bid and confirm it routes correctly through the integration into the rostrum console.
Absentee-bid execution — confirm pre-loaded absentee bids fire at the correct moments during the test lots.
Failover drills — kill the primary internet link, kill the primary camera, kill the primary mic. Confirm each failover is sub-30-second.
Run the rehearsal with the actual auctioneer who will run the sale, not a stand-in. Auctioneers have voice, tempo, and gesture habits that affect mic placement and camera framing.
Latency budgets — the number that matters
The single quantitative spec that drives simulcast quality is the end-to-end latency from auctioneer's call to the bid arriving back at the rostrum from a remote bidder. Break it down:
Segment
Target
Typical poor-stack figure
Auctioneer call → encoder
<50ms
100–200ms
Encoder → CDN edge
100–150ms
300–500ms
CDN edge → bidder device
100–150ms
500–1500ms
Bidder device render → human reaction
200–300ms
200–300ms
Bidder bid → server
50–100ms
200–500ms
Server → rostrum console
<50ms
100–200ms
Total round trip
<450ms
2–4 seconds
Auction Rabbit's stack targets and consistently delivers sub-450ms round-trip — see the Web platform for the full architectural detail. This is the threshold at which online bidders behave indistinguishably from floor bidders in observed bid timing data.
A stack at 2+ seconds round-trip produces a predictable and damaging pattern: floor bidders win lots online bidders would have taken, online bidders abandon the platform after 5–10 lots, and consignors notice their realised prices underperforming sale-day expectations. The fix is structural, not configurable — you need a low-latency-engineered platform end to end, not just a CDN tweak.
Absentee and phone-bid routing
Simulcast doesn't replace absentee and phone bids; it adds a fourth channel alongside them. The four channels must reconcile cleanly into one ledger.
Absentee bids
Pre-loaded into the system before the sale. The platform fires the absentee bid automatically at the appropriate increment when bidding crosses below the absentee maximum. The platform should never expose the absentee maximum to anyone except the system — neither the bidder, nor competing bidders, nor the auctioneer mid-lot.
Phone bids
A staffed phone-clerk operation parallel to the simulcast. Phone-clerks hold a registered bidder on the line, listen to the auctioneer, and call out bids on the bidder's behalf. The phone-clerk presses a "phone bid" button on a tablet that registers the bid in the rostrum console identically to a floor or online bid.
Phone-bid staffing is the most expensive part of the simulcast operation per lot. Major houses run 1 phone-clerk per 4–8 simultaneous phone bidders. For high-value sales, expect 30+ phone-clerks at a single sale.
Clerking under simulcast
The clerk's job is harder under simulcast than at a floor-only sale. Floor bids alone are easy — paddle numbers visible, live in the room. Simulcast clerks must:
Confirm hammer to the right channel (floor/phone/online/absentee)
Capture the right paddle/bidder ID for the winning channel
Record the hammer figure correctly (most platforms auto-fill but human verification matters)
Mark "passed" lots cleanly with the highest underbid recorded for after-sale work
Time-stamp every event for the audit trail
Use a two-clerk setup for any sale above ~200 lots: a primary clerk on the live feed and a secondary clerk reconciling the catalogue file in real time. Single-clerk operations introduce reconciliation errors at a rate of roughly 1 in 200 lots, which compounds across a sale year into real money.
Common failure modes
These are the failures that have cost houses real money and reputation. Plan for each.
Audio dropout
The auctioneer's wireless mic fails for 5–30 seconds. Online bidders see the auctioneer gesturing but hear nothing. Bid behaviour collapses for the affected lot.
Mitigation: wired backup mic always live; auto-cut to backup on dropout. Brief the auctioneer to verbalize "audio is restored, continuing from $X" when the audio recovers.
Latency spike
Network congestion or CDN issue pushes round-trip latency from 400ms to 3+ seconds. Online bidders find their bids arriving late and being beaten by floor bids.
Mitigation: monitor latency in real time during the sale. If latency spikes above 1 second sustained for >30 seconds, the auctioneer slows tempo deliberately to compensate. If the platform shows >2 seconds, pause the sale and investigate.
Encoder failure
The hardware encoder crashes. The broadcast goes black for 30–120 seconds.
Mitigation: redundant encoder pre-warmed; automatic failover. If failover takes >60 seconds, pause the sale and announce to the room.
Phone-bid line drops
The phone-clerk loses connection to a bidder mid-lot.
Mitigation: phone-clerk must signal the auctioneer immediately. Auctioneer either holds the lot for 30 seconds while the line is restored or proceeds without that bidder. Never proceed past hammer with an unresolved phone connection.
Online bidder ID conflict
Two bidders are bidding under the same account by accident or fraud. Hammer goes to an account that contests the win.
Mitigation: strong identity verification at registration (KYC), single-session enforcement, and real-time fraud signals. Auction Rabbit's identity layer flags multi-session conflicts before the hammer falls.
Settlement mismatch
The catalogue shows lot 47 hammered at $48,000 to paddle 213 (online); the payment system shows paddle 213 has not paid; the consignor's payout calculation runs without confirming the buyer is real.
Mitigation: never settle the consignor before buyer payment confirmation. Standard 30–45 day buyer-payment grace; consignor remit triggered on buyer-paid status, not on hammer event.
Post-sale settlement reconciliation
The hammer event is not the transaction. Settlement is. After the sale closes, the operations team must reconcile every line of the ledger, confirm buyer payment, and remit consignors. Standard cadence:
Buyer payments incoming. Phone-bid and absentee bidders confirmed.
7
First payment-chase email to non-paying buyers.
14
Second payment-chase + late-fee notice.
21
Buyer default declared on non-payers. Lot offered to underbidder.
30–45
Consignor settlement on paid lots.
60
Bought-in / after-sale negotiation window closes.
90
Final reconciliation of all unsold lots, returns, refusals.
Auction Rabbit's settlement pipeline automates the reconciliation flow end-to-end — buyer invoicing, payment chasing, consignor payout calculation, and 1099-K / VAT reporting — see the Web product and contact to see how it integrates with the simulcast layer.
How-to steps
How to run a live simulcast auction
Step 01
Specify the hardware stack
Three cameras minimum (auctioneer, lot, room), wireless mic with wired backup, hardware encoder, dual internet uplinks bonded, rostrum console for the auctioneer, separate clerk station.
Step 02
Choose the software platform
Integrated platforms (auctioneer + bidder + clerk + broadcast in one stack) reduce reconciliation gaps. Verify the platform's measured end-to-end latency — sub-450ms is the standard.
Step 03
Configure absentee and phone-bid integration
Pre-load absentee bids; confirm they fire automatically. Set up phone-clerk stations with tablet-based bid buttons routed into the rostrum console.
Step 04
Run the pre-sale tech rehearsal
24–72 hours before sale. Full end-to-end test with real auctioneer, real lot table, real cameras, real mic. Test failover for primary internet, primary camera, primary mic.
Step 05
Brief the auctioneer on simulcast tempo
Auctioneer must allow ~250–350ms beat for online bids before hammering. Brief on the rostrum-console layout and the latency monitor.
Step 06
Run the sale with active monitoring
Designated tech operator watches latency, encoder health, mic levels, and bidder-count dashboard live. Pre-agreed pause protocol if latency exceeds 1 second sustained or any feed drops.
Step 07
Lock the catalogue at sale end
Clerks complete the lot ledger. Two-clerk reconciliation. Catalogue locked within 30 minutes of last lot.
Step 08
Issue invoices within 4 hours
Automated invoicing to all winning bidders. Include hammer, premium, tax, shipping, payment instructions, payment deadline.
Step 09
Run the settlement reconciliation flow
Buyer payment in 0–14 days; payment chase 7/14 days; default declared at 21 days; consignor remit at 30–45 days on paid lots only.
Step 10
Post-mortem the sale
Within one week of sale: review latency log, audio/video drop incidents, online bidder behaviour, sell-through by channel. Adjust the stack and process for the next sale.
Common questions
A simulcast auction is a live in-room sale broadcast in real time to remote bidders over the web and mobile, with online bids clerked into the same ledger as floor, phone, and absentee bids. The auctioneer sees all four channels on a rostrum console and hammers to whichever channel has the highest active bid at the moment of the hammer.
Sub-450ms end-to-end round-trip (auctioneer call to remote bid back at the rostrum) is the threshold for online bidders to behave indistinguishably from floor bidders. Above 1.5 seconds, online bidders consistently lose to floor bids and abandon the platform within 5–10 lots. Auction Rabbit's platform consistently delivers sub-450ms.
Three cameras (auctioneer, lot, room), a wireless lavalier on the auctioneer with a wired backup mic, an audio mixer, a hardware encoder (LiveU, Teradek), bonded internet with two independent uplinks, a rostrum console for the auctioneer, and a separate clerk station. Mid-market house budget for the hardware stack runs $25k–$80k as a one-time investment plus $500–2,000 per sale day operational.
All four channels (floor, phone, online, absentee) feed into the rostrum console and are clerked into a single ledger. The auctioneer hammers to whichever channel has the highest active bid. Absentee bids fire automatically when the live bidding crosses below the absentee maximum; phone-clerks press a tablet button to register their bidder's call; online bidders click directly. The system time-stamps and channels each bid for the audit trail.
Audio dropouts (most common — fix with a wired backup mic always live), latency spikes (mitigate with active monitoring and pre-agreed slow-tempo protocol), encoder crashes (redundant pre-warmed encoder), phone-bid line drops (phone-clerk signals the auctioneer immediately), and settlement mismatches (never settle consignor before buyer payment is confirmed).
For most houses, use an integrated platform. The latency engineering, multi-channel reconciliation, identity verification, and settlement pipeline are non-trivial to build and harder to maintain. Mixed-vendor stacks introduce sync gaps between auctioneer, clerk, broadcast, and payment layers. Houses with above ~$200M annual GMV sometimes build proprietary stacks for cost reasons; below that, integrated platforms win on TCO and reliability.