How it works
Vistacast does not imitate anyone else's protocol. Both halves are ours, the app that sends and the app that receives, which is why it keeps working across iOS releases instead of breaking with them. Here is the whole chain, end to end.
Discovery
The receiver announces itself on your local network using mDNS, the same zero-configuration protocol your printer uses to appear without you typing an address. Your iPhone listens for those announcements and lists whatever it finds. Nothing is registered anywhere, and no lookup leaves your network.
Capture
iOS hands the app your screen through ReplayKit, the system's own screen-recording interface. This is why the confirmation you see when you start comes from iOS itself rather than from us: the operating system controls the capture, not the app.
Encoding
Frames are compressed to H.264 by the iPhone's dedicated video hardware rather than in software, which is what keeps the phone from overheating and the battery from draining faster than it already does with the screen on. Audio is encoded separately as AAC.
Transport
The compressed stream travels over a direct TCP connection from the phone to the television, across your own Wi-Fi. There is no server in the path because there is no server at all. The connection is encrypted when your television can negotiate it, and falls back to an unencrypted local connection on the chipsets that cannot.
Decoding and sync
The television decodes both streams in hardware and lines them up against a shared clock, so the audio stays matched to the picture instead of drifting apart over a long session.
Adaptation
Throughout, the receiver reports back on how well it is keeping up. Quality and bitrate step down when your network is struggling and recover when it improves, with deliberate cooldowns so the picture settles rather than oscillating.
Questions this usually raises
- Why does Vistacast need an app on the television?
- Because the alternative is worse. Apps that avoid a TV-side install do it by imitating a closed protocol they do not control, which means they break whenever the other side changes. Owning both halves means the protocol is ours, and an iOS update does not silently end the product.
- Does anything go through the internet?
- No. There is no backend, no account and no telemetry in the shipped apps. Your screen goes from the phone to the television across your own network. If your internet connection dropped entirely, mirroring would keep working.
- Is the connection encrypted?
- It is encrypted when your television can complete the handshake, and some chipsets cannot. On those, the app falls back to an unencrypted connection within your local network so that mirroring still works. The receiver is also not authenticated yet, so on a network you do not control another device could in principle present itself as a receiver. On a home network this is not a practical concern, but we would rather state it than imply more than is true.
- What resolution does it send?
- Vistacast scales the picture to fit the television rather than sending your screen at its full pixel dimensions. The result is sized for comfortable viewing across ordinary home Wi-Fi rather than for a specification sheet.
- Why can it not mirror Netflix?
- Copy-protected video is blocked by iOS at the operating-system level, below where any third-party app operates. Every screen-mirroring app on iOS has this limit, and any that claims otherwise is not describing protected content.
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