The cut never leaves the edit bay
A conferencing app re-encodes your picture twice and crushes the grade your colorist spent a day on. Screener does not touch it: the file is read in slices where it sits, the slices cross a direct connection, and the client’s browser plays the exact bytes on your disk. No upload, no copy in a bucket, no screen share.
A byte stream, not a file transfer
The player is handed chunks as they arrive and drops what it has played. Sending waits on the channel’s own buffer rather than on a timer, so a slow seat slows its own stream and nobody else’s.
- Preflight before anyone is invited. The container is sniffed and the whole file is hashed. A plain MP4 with its index at the end is refused now — with the ffmpeg command that fixes it — rather than stalling five minutes into the screening.
- The door is host-locked. A browser that reaches the room gets no bytes until you admit it.
- Everybody sees the same frame. You pace the room; drift is absorbed by playing imperceptibly faster or slower, never by a visible seek.
- Approval is a certificate. It hashes the file that actually streamed into an append-only chain, with the number of notes still open at that moment. “Looks great!” in a chat thread is worth nothing on a disputed invoice.
webm · plays from a byte stream 2.1 Mbps per seat 6.3 Mbps up at 3 seats sha-256 9c8f736e…1715 SEATS 3 of 10 priya 100% sent 12s buffered marcus 100% sent 9s buffered ana 74% sent 3s buffered NOTES 2 open 00:41:22 the door cut is late 01:02:08 grade drifts warm
What “the client never holds the file” actually means
There is no download button and no file on disk: chunks are appended to the player and the played ones are dropped. That is cooperative eviction — the page drops them because the page is written to. A determined viewer running a modified client can keep what it is sent, and anything that reaches a screen can be filmed off it. This is a review tool that stops a cut drifting into somebody’s downloads folder; it is not DRM, and a page that claimed otherwise would be lying to the person who most needs the truth.
The container, honestly
A browser plays a byte stream, not a file. WebM works as it is, and so does fragmented MP4. A plain MP4 keeps its index at the end, so a player would need the last bytes first — and that is the file most people actually have. Today Screener refuses it with the one-line ffmpeg command that converts it. In-browser remux is not built yet, and until it is, that first step is real friction rather than a footnote.
Not a broadcast platform
The host sends one copy per viewer. A 3 Mbps cut to six people is 18 Mbps of upload, which is a screening, a review or a film club — not an audience. The number is on screen before you press play, because the alternative is a room that degrades and blames the wifi.
What it costs
Commercial — per screening room, per month
A licence per bay, checked when the console opens. Without one the screening still runs and every
certificate it writes is stamped licensed:false.
The part that matters, in the open
Sending waits on the channel's own buffer and resumes on bufferedamountlow — never on a fixed sleep, which is a guess about somebody else's network.
send: (buf) => dc.send(buf),
bufferedAmount: () => dc.bufferedAmount,
readyState: () => dc.readyState,
onLowWater: (threshold, fn) => {
dc.bufferedAmountLowThreshold = threshold;
dc.onbufferedamountlow = () => { dc.onbufferedamountlow = null; fn(); };
},Taken from this app's source, not written for the page. Built on the Messaging Platform SDK.