the odd semi hd 1024x576 resolution is from way back and not valid anymore they are changed to 720x480.
but I am pretty sure all the real hd channels are still valid. only the 1024x576 channels have changed.
you can check them yourself in kodi, press 'o' while the video is running.
that being said they are very much watchable imho.
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actually the correct sd format for 30 fps (or 29.970 fps) us channels is 704x480. and for 25 fps uk channels 720x576.
but that's another story.