you need to update mpurlsourcesplitter, I made some fixes for playback of webm (MediaPortal IPTV filter and url source splitter is now at 2.2.24)
Thats right, i am also facing the same issue, btw. i tested with LAV
[07-22 00:56:43,579] [OnlineVideos] [DEBUG] GetWebData-GET: 'https://api.zdf.de/tmd/2/ngplayer_2_4/vod/ptmd/mediathek/210709_london_boulevard_trailer_spf'
[07-22 00:56:46,240] [MPMain ] [INFO ] Preparing graph for playback of 'https://nrodlzdf-a.akamaihd.net/dach/zdf/21/07/210709_london_boulevard_trailer_spf/2/210709_london_boulevard_trailer_spf_2128k_p18v15.webm'
[07-22 00:56:47,414] [OnlineVideos] [INFO ] Start prebuffering ...
[07-22 00:56:47,415] [OnlineVideos] [INFO ] BufferFile : using 'MediaPortal IPTV filter and url source splitter' as source filter
[07-22 00:56:47,417] [OnlineVideos] [INFO ] BufferFile : loading url: 'https://nrodlzdf-a.akamaihd.net####Url=https%3a%2f%2fnrodlzdf-a.akamaihd.net%2fdach%2fzdf%2f21%2f07%2f210709_london_boulevard_trailer_spf%2f2%2f210709_london_boulevard_trailer_spf_2128k_p18v15.webm&'
[07-22 00:56:48,176] [OnlineVideos] [DEBUG] Buffering: 767/43511 KB (1%)
[07-22 00:56:48,228] [OnlineVideos] [DEBUG] Buffering: 43510/43511 KB (99%)
[07-22 00:56:53,077] [OVGraph ] [DEBUG] BufferFile : Rendering unconnected output pins of source filter ...
[07-22 00:56:53,187] [OVGraph ] [DEBUG] BufferFile : Playback Ready.
[07-22 00:56:53,230] [OnlineVideos] [INFO ] Prebuffering finished.
[07-22 00:56:53,257] [MPMain ] [INFO ] OnlineVideosPlayer: Play 'https://nrodlzdf-a.akamaihd.net/dach/zdf/21/07/210709_london_boulevard_trailer_spf/2/210709_london_boulevard_trailer_spf_2128k_p18v15.webm'
[07-22 00:56:53,262] [MPMain ] [WARN ] OnlineVideosPlayer: Failed to render file -> No video renderer connected
That could be the reasonor it's geoblocked...