dlna-cast

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Mirror your Linux desktop (or use the TV as a second monitor) to a smart TV over DLNA, with sound. No Miracast, no Chromecast, no app on the TV: it uses the TV's built-in DLNA media player.

A small Python package with no dependencies beyond PyGObject and GStreamer. It captures the screen through the Wayland screen-cast portal, encodes it with GStreamer and plays it on the TV as a live MPEG-TS stream.

• Mirror mode: the TV shows one of your screens.
• Extend mode (--extend): the TV becomes a separate virtual monitor; drag windows to it.
• Finds the TV automatically, recovers if the TV stops the stream or your IP changes.
• Steady 60 fps output, hardware encoding on NVIDIA (NVENC) or Intel/AMD (VA-API), x264 as a fallback.

Latency is about 3 seconds (TV-side buffering in DLNA). Good for videos, films and presentations; not for using the mouse on the TV.

Requirements

• Linux with a Wayland session and xdg-desktop-portal (KDE Plasma or GNOME).
• PipeWire (default on current distributions).
• A TV that acts as a DLNA/UPnP MediaRenderer on the same network. Tested on a Samsung UE49KS8500 (Tizen, 2016). Most Samsung, LG, Sony and Philips smart TVs have one; reports for other models are welcome.
• Python 3.9+ with PyGObject, and GStreamer 1.20+ with the plugins below.

GNOME, VA-API and other TVs should work but haven't been tested yet. Extend mode needs a portal that supports virtual monitors (KDE Plasma 6 does; GNOME doesn't).

Installation

Install the dependencies, then download the script:

Fedora (enable RPM Fusion for x264 and AAC):

sudo dnf install python3-gobject gstreamer1-plugins-base gstreamer1-plugins-good \
    gstreamer1-plugins-bad-free gstreamer1-plugins-ugly gstreamer1-plugin-libav \
    pipewire-gstreamer pulseaudio-utils

Ubuntu / Debian:

sudo apt install python3-gi gir1.2-gstreamer-1.0 gstreamer1.0-plugins-base \
    gstreamer1.0-plugins-good gstreamer1.0-plugins-bad gstreamer1.0-plugins-ugly \
    gstreamer1.0-libav gstreamer1.0-pipewire pulseaudio-utils

Arch:

sudo pacman -S python-gobject gst-plugins-base gst-plugins-good gst-plugins-bad \
    gst-plugins-ugly gst-libav gst-plugin-pipewire libpulse

Then:

git clone https://github.com/tamerardall/dlna-cast.git
cd dlna-cast
./main.py --list      # should show your TV

./main.py runs straight from the checkout. To get a dlna-cast command instead, install it with access to the system PyGObject:

pipx install --system-site-packages .

For NVIDIA hardware encoding you need the proprietary driver; the nvcodec plugin is part of plugins-bad. For Intel/AMD, the va plugin (plugins-bad) plus the VA-API driver for your GPU.

Usage

Turn the TV on, then:

./main.py             # mirror
./main.py --extend    # TV as a second monitor

On first start your desktop asks which screen to share. The choice is remembered in ~/.config/dlna-cast/; delete that folder to choose again. Stop with Ctrl+C (the TV is told to stop as well).

If there are several TVs, or discovery fails, pass the TV's IP: ./main.py 192.168.1.50. ./main.py --list shows what was found.

Options

The output is always 1920×1080; other screen sizes are scaled with black borders.

Status line

Every 5 seconds:

fps: source 50/s, output 60/s, longest gap 25 ms, dropped chunks total 0

• source: new frames from the screen. The compositor only sends frames when something changes, so a low number on a still screen is normal.
• output: frames sent to the TV. Should always be ~60.
• longest gap: longest pause in the data sent to the TV. Above ~50 ms you'll see stutter.
• dropped chunks: non-zero means the TV (or the network) can't keep up.

How it works

1. The screen is captured through xdg-desktop-portal (the only sanctioned way on Wayland) as a PipeWire stream.
2. GStreamer encodes video (HEVC/H.264) and desktop audio (AAC) into MPEG-TS. A live black 60 fps background drives a compositor, so the output runs at a fixed rate even when the screen is still.
3. A small HTTP server on port 8765 serves the stream.
4. The TV is told to play that URL with UPnP SetAVTransportURI + Play. The control URL is read from the TV's device description found via SSDP.

Security

The HTTP server listens on 0.0.0.0:8765 with no authentication. While it runs, anyone on the same network (including VPNs like Tailscale) can watch your screen at http://<your-ip>:8765/screen.ts. Stop it when you're not using it and don't run it on untrusted networks.

Troubleshooting

• TV not found: TV on and on the same network/subnet? Some routers block multicast (SSDP) between Wi-Fi and Ethernet; pass the IP by hand. ./main.py --list shows what answers.
• Nothing on the TV: check the log for SetAVTransportURI -> 200. Anything else means the TV refused the stream; please open an issue with the log. Play -> 500 is harmless on Samsung (it starts playing by itself).
• Stutter: ping the TV and look for packet loss. Use 5 GHz Wi-Fi for the computer, move the TV closer to the router, or lower --bitrate.
• Low frame rate under motion: check which encoder the log says it chose. With NVIDIA use nvautogpuh265enc (what nvenc selects); the plain nvh265enc dropped the live source to ~20 fps in testing.
• Laptop screen turns off in extend mode (KDE): KWin sometimes applies a stored layout that disables the built-in screen when the virtual monitor appears. The script turns it back on and moves the virtual monitor to the right with kscreen-doctor.
• No screen sharing dialog: make sure a portal backend is running (xdg-desktop-portal-kde or -gnome): busctl --user list | grep portal.
• No sound: the log says what's missing (pactl, pulsesrc or an AAC encoder).

Known limitations

• ~3 s latency; inherent to DLNA playback.
• Miracast was tried and failed with this TV (P2P-GO-NEG-FAILURE); DLNA is more reliable.
• On some NVIDIA drivers NVENC only encodes HEVC (Codec not supported for H.264), which is why nvenc uses HEVC. TVs older than ~2016 may not play HEVC; use --encoder x264 then.
• If the TV's own IP changes while running, restart the script.

Contributing

Bug reports and reports of working/non-working TVs are very welcome, see CONTRIBUTING.md.

License

MIT