I always wondered if this was a deliberate pre-show test of the transmission channel's compression. I remember noticing as a kid that some channels on cable TV

I always wondered if this was a deliberate pre-show test of the transmission channel's compression. I remember noticing as a kid that some channels on cable TV were noticeably worse quality (far more blocky iirc, looked very MPEG artifacty) than the analogue broadcast equivalent and that others looked very different between even cable and satellite tv (iirc More4 was one of the more obvious ones, looked OK on Sky but awful on NTL). The HBO static intro screen was worst case for compression but gave a pretty good indication of the quality (of the bitrate/compression) of the rest of the show; which worked for broadcast, recordings or downloads. Probably not deliberate, but actually kinda useful.