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Third-Party Encoder - MTU & Black Screen Issues

Black livestream video​

In some network environments, remote participants may see a black livestream video feed (stream is subscribed, but the output is black). This can happen when video packets are dropped due to network MTU (Maximum Transmission Unit) limits, which are common on corporate networks, VPNs, or IPSec tunnels.

When packets are dropped, the video stream cannot be decoded correctly and appears as black frames.

If you experience black video when using a third-party encoder (for example, Magewell Ultra):

  • Set encoder MTU to 1000
  • If available, reduce video bitrate (for example to 1000 kbps)
  • Restart the encoder and rejoin the Louper room

These settings have resolved black screen issues in real-world customer environments.

Why this happens​

Some networks do not support large UDP packets. When an encoder sends packets that exceed the network’s supported MTU, the packets may be fragmented or silently dropped. Because Louper uses browser-based video playback, dropped packets can result in missing video frames, which appear is a black video stream.

If the issue persists​

If lowering the MTU does not resolve the issue:

  • Check whether the network path includes a VPN or IPSec tunnel
  • Work with your network team to bypass the tunnel or increase supported MTU
  • Contact Louper Support at support@louper.io with details about your encoder model and network setup