Options & settings

Every command-line flag, and where the saved settings live.

Saved settings

Whatever the control page applies is written to config.json:

Windows: %APPDATA%\web2sdi\config.json
Elsewhere: $XDG_CONFIG_HOME/web2sdi/config.json, or ~/.config/web2sdi/config.json

It is plain JSON on purpose, so an operator who cannot reach the web UI can still read and fix it by hand:

{
  "url": "https://example.com",
  "device": 0,
  "mode": "1080p59.94",
  "width": 0,
  "height": 0,
  "fps": 0,
  "audio": false,
  "audio_offset_ms": 0,
  "video_delay_ms": 50,
  "bind": "localhost",
  "port": 8787
}

A width, height or fps of 0 follows the SDI mode. bind is localhost or lan.

Command-line flags

Flags override the saved settings for that run only.

Source and output

Flag	What it does
`--url <url>`	The page to render. Default `https://example.com`.
`--sink <decklink\|file>`	Where frames go. Default `decklink`; `file` writes PNGs.
`--device <n>`	DeckLink device index. Default `0`.
`--mode <mode>`	SDI mode, e.g. `1080p59.94`, `1080i50`, `720p59.94`.
`--width <n>` / `--height <n>`	Browser render size. Default: match the SDI mode.
`--fps <n>`	Browser frame rate. Default: match the SDI mode.
`--pixel-format <bgra\|yuv>`	The pixel format on the wire.
`--seconds <n>`	Stop after n seconds. `0`, the default, runs until stopped.

A render smaller than the SDI frame is centred in it rather than scaled up.

Supported modes are 1080p59.94, 1080p60, 1080p50, 1080p30, 1080p29.97, 1080p25, 1080p24, 1080i59.94, 1080i50, 720p59.94, 720p50, NTSC and PAL. Which of those a given card will actually take — and in which pixel format — is what dltest --probe reports. A Duo 2, for one, will not take BGRA at 1080p59.94, so web2sdi converts to YUV there.

Audio

Flag	What it does
`--audio`	Embed the page's audio in the SDI output.
`--video-delay-ms <n>`	Hold video back to meet Chromium's audio delay. Default `50`.
`--audio-offset-ms <n>`	Trim audio later (+) or earlier (−) against video.
`--audio-continuous`	A continuous audio stream instead of timestamped scheduling.

The default video delay is calibrated for the Chromium version web2sdi ships. It is worth re-measuring with dlsync after an upgrade — see How it works.

Control page and preview

Flag	What it does
`--port <n>`	Control page port. Default `8787`.
`--lan`	Serve the control page on the network.
`--preview-width <n>` `--preview-height <n>`	The box the preview is scaled into. Default 1280×720.
`--preview-fps <n>`	Preview frame rate. Default `30`.
`--preview-quality <n>`	Preview JPEG quality. Default `70`.

Encoding the preview is the one part of web2sdi that costs real CPU — about a quarter of a core at the defaults. The preview slots are sized once at startup, so changing them needs a restart.

File sink

For development without a card: --sink file writes PNGs instead.

Flag	What it does
`--out-dir <dir>`	Where to write. Default `/tmp/frames`.
`--every <n>`	Write every _n_th frame. Default `30`.
`--max-frames <n>`	Stop after n files. `0` runs until stopped.

Other tools

Two small programs ship beside web2sdi.exe:

dltest --probe lists every sub-device on the card and the modes and pixel formats each will accept. Without --probe it plays a test pattern, which is the quickest way to prove the card and cabling work on their own.
dlsync measures A/V sync over an SDI loopback cable.