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Casting (DLNA)

Stream to Chromecast and DLNA devices

CineWindows can stream media to Chromecast, DLNA-compatible TVs, and UPnP media renderers on your local network. The CastService handles device discovery via UPnP SSDP and sends media URLs using SOAP-based AVTransport control.

How Casting Works

The CastService uses UPnP (Universal Plug and Play) to discover and control media renderers:

  1. Discovery — Sends an SSDP M-SEARCH multicast to 239.255.255.250:1900 requesting MediaRenderer:1 devices
  2. Description — Devices respond with a description URL; the service fetches the XML and extracts the friendlyName and AVTransport control URL
  3. Streaming — Sends the media URL to the device via SetAVTransportURI SOAP action, followed by a Play command
UPnP AV Transport 1.0 SSDP v1.0

Device Discovery

Trigger discovery from the Cast dialog (Media > Cast). The service broadcasts an M-SEARCH request with a 2-second MX (response wait time) and collects responses for 3.5 seconds total. Compatible devices appear in a list as they are found.

Discovery Process

M-SEARCH * HTTP/1.1
HOST: 239.255.255.250:1900
MAN: "ssdp:discover"
MX: 2
ST: urn:schemas-upnp-org:device:MediaRenderer:1

The service listens on a UDP socket bound to QHostAddress::AnyIPv4. Each response is parsed for the LOCATION header, which points to the device’s XML description. The description is fetched over HTTP, parsed with QXmlStreamReader, and registered if it exposes an AVTransport service with a controlURL.

Device Information

Discovered devices provide:

  • Name — friendlyName from the device description (e.g. “Living Room TV”, “Office Chromecast”)
  • Control URL — SOAP endpoint for AVTransport commands
  • Description URL — Device description URL for metadata

Streaming a URL

Once a device is selected, CineWindows sends the media URL to the device via a SOAP XML envelope:

SetAVTransportURI

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"
  s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
  <s:Body>
    <u:SetAVTransportURI xmlns:u="urn:schemas-upnp-org:service:AVTransport:1">
      <InstanceID>0</InstanceID>
      <CurrentURI>https://example.com/video.mp4</CurrentURI>
      <CurrentURIMetaData></CurrentURIMetaData>
    </u:SetAVTransportURI>
  </s:Body>
</s:Envelope>

Play

Immediately after the URI is set (on success), the service sends a Play SOAP action:

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"
  s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
  <s:Body>
    <u:Play xmlns:u="urn:schemas-upnp-org:service:AVTransport:1">
      <InstanceID>0</InstanceID>
      <Speed>1</Speed>
    </u:Play>
  </s:Body>
</s:Envelope>

Same-Network Requirement

Both your computer and the casting device must be on the same local network. UPnP SSDP discovery uses multicast (239.255.255.250) which does not route across subnets or through NAT. The media URL must also be accessible from the casting device — local file paths will not work unless served by an HTTP server reachable on the LAN.

Casting Steps

Connect Devices to the Same Network

Ensure your computer and the target device (Chromecast, DLNA TV, etc.) are on the same Wi-Fi or wired network. Devices on separate VLANs or guest networks will not discover each other.

Open the Cast Dialog

Click Media > Cast from the menu bar or right-click the video and select Cast. The Cast dialog opens with a Discover Devices button and a device list.

Discover Devices

Click Discover Devices. The service broadcasts SSDP and lists every found MediaRenderer on the network. Discovery runs for ~3.5 seconds. If no devices are found, the dialog shows a “No compatible devices found” message.

Select a Device

Click a device name from the list. CineWindows immediately sends the currently-playing media URL to the device.

Streaming Begins

The device starts playback. CineWindows shows a confirmation toast. The local player continues playing independently — casting does not stop local playback. Use the device’s own controls (remote, TV interface) to pause, seek, or stop.

Supported Devices

CineWindows’ UPnP implementation is compatible with:

  • Chromecast (1st, 2nd, 3rd gen, Chromecast Ultra, Chromecast with Google TV)
  • Google Nest Hub and Nest Max
  • DLNA-certified TVs (Samsung, LG, Sony, Panasonic, Vizio)
  • Game consoles (PS4, PS5, Xbox One, Xbox Series X/S — DLNA mode)
  • Software renderers (VLC in renderer mode, Plex, Universal Media Server)

Note that Chromecast requires the media URL to be an HTTP/HTTPS link. Local file paths will not cast to Chromecast devices.

Limitations

The first release of casting supports:

  • HTTP/HTTPS URLs only — local files and YouTube links resolved by yt-dlp are not cast directly. To cast YouTube content, use the Chromecast’s native YouTube app.
  • No playlist support — single media URL per cast session
  • No transport monitoring — CineWindows does not poll the device for playback position or status after casting starts
  • No queuing — subsequent cast actions replace the current URI

These limitations are expected to be addressed in future releases as the cast service matures.

Troubleshooting

No devices found — Check that all devices are on the same network. Verify UPnP is enabled on the target device (often in network settings). Try disabling and re-enabling the network interface. Some corporate or guest networks block SSDP multicast.

Device found but cast fails — Ensure the media URL is accessible from the casting device. Test by opening the URL in a browser on the device. Check that the URL uses HTTP or HTTPS — local files are not supported.

Playback does not start — The device may not support the media format. Try a standard MP4 with H.264 video and AAC audio. Some devices require specific container formats.

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