Four, CBBC and CBeebies now downconvert to 576i on their SD outlets. BBC One and Two have been doing this for some time.
CBBC and CBeebies haven't had the HD bug for some time now.
Which begs the question...
BBC THREE's refresh last year before being moved online lacked an HD bug on the DOG. Was it also down converted to SD (like with FOUR, CBBC, CBeebies), or was it two versions of the channel?
Last time I check it was full resolution (DSat & Freeview) so either 720/704x576
Looking at Digital Bitrate - resolution is 704x576 across BBC SD channels on Freeview, 720x576 for Sky/Freesat/Virgin.
And now, in theory, that the channel is sourced entirely from HD - 704x576 is all you should need, as 1920x1080 will be downscaled to 702x576, leaving nothing to go in the 8 additional samples each side in a 720x576 frame vs a 704x756 one? (*)
(*) Apart - possibly - from an edge case with 4:3 content.
I noticed yesterday BBC Four have changed their DOG again. It is now smaller and fainter than before - it may be how the HD DOG was, but without the HD tag, though as I'm don't receive BBC Four HD, I can't say for sure. Now it's so small and faint, I really can't understand why they still don't have the confidence just to drop it altogether?