External mp4 camera not streaming

Hi !
With the config below in configuration.yaml I can add the camera entity to a picture-glance card

  - platform: generic
    name: a102_Flyover
    stream_source: https://s3-eu-west-1.amazonaws.com/jamcams.tfl.gov.uk/00001.03111.mp4
    still_image_url:  https://s3-eu-west-1.amazonaws.com/jamcams.tfl.gov.uk/00001.03111.jpg

But only the still image works, not the mp4.

2021-01-12 07:42:33 ERROR (stream_worker) [homeassistant.components.stream.worker] Error demuxing stream: 

If I open the link in a browser it works fine though …

thanks