Well, I’m watching it again now, it’s got a genuine ‘50i fluid’ look
Ah - I'm careful to say 50Hz not 50i these days as there is so much 50p knocking around
Are you saying it’s 720p50 ?
Unless you are watching on Sky HD - then it's almost certainly a 1080i25 to 720p50 deinterlace. The highest quality (non-'UHD') iPlayer format (other than on Sky HD) is 720p50. There is also a 540p50 profile at a lower bitrate. The lower-than-540p profiles are p25 not p50. For legacy platforms there are also 720p25 streams still I believe. (These are SDR Rec 709 H.264/AVC 8-bit.)
For UHD iPlayer (which is also HLG) there are 2160p50, 1440p50 and 1080p50 (and possibly a 720p50 now?) streams in H.265/HEVC 10-bit HLG Rec 2020 for live, and there are p25 variants for pre-recorded stuff. (Dynasties is 2160p25)
Sky HD uses Sky's in-house distribution system and uses progressive download (You can start watching before the download has completed but it won't let you start until it thinks it's got enough for you not to run out). I think it's around 8Mbs 1080i25 H.264 (and can carry 5.1 Dolby Digital - all other iPlayer outlets are 2.0 AAC ISTR)
It could be, but looks the same quality as ‘broadcast’ 1080i50 !
It's around 5Mbs so survives OK - but demanding content exposes the less-than-ideal deinterlacing and compression used - particularly on live stuff. Strictly hammers iPlayer...
BTW 50i from the start this time, so must have been some bandwidth starvation first time round ?
Yes - I guess so.