Originally Posted by A_Smith
not sure I get it ... They all use the same standards for broadcasting, best picture is only a matter of bandwidth
They use the same basic technical interconnect standards in production, but not always to the same quality, and the transmision standards vary country by country.
Some countries are using mainly H264 (aka MPEG4) for HD broadcasting to the home, others are still using MPEG2. H264 delivers is a much more modern system, and capable of delivering decent quality at lower bitrates, with far less objectionable compression artefacts. (In Europe there are no major MPEG2 HD broadcasts to the home anywhere - HD = H264 here)
Some countries have a distribution infrastructure based around compressed distribution with multiple MPEG2/MPEG4 encode/decodes between the viewer and the source material, whilst others may only have a single encoder at the end of a centralised broadcast chain.
All of these make a major difference in picture quality terms.
Sky in the UK, for instance, will have just a single H264 encoder between their HD-SDI playout area and the viewer at home. Other broadcasters may use MPEG2/MPEG4 to distribute to a local station, then that station will decode this to HD-SDI and re-encode to MPEG2 for OTA broadcast, and there could be further decode/recodes if the signal is then broadcast on satellite as well. This concatenation of codecs hammers picture quality.
Of course there are differences in standards upstream of the distribution and transmission systems.
Some broadcasters may still accept transmission masters on HD Cam tape (1440x1080 3:1:1) whilst others may mandate HD Cam SR (1920x1080 4:2:2 or 1280x720 4:2:2). Some may mandate a minimum acquisition bitrate of 50Mbs Long GOP or 100Mbs Intra, whilst others may accept 35Mbs Long GOP (aka Sony XD Cam EX) or even 25Mbs Long GOP (aka HDV) for acquisition. Some may accept Super 16mm as being suitable for HD broadcast, others may not. Some may standardise on DVC Pro HD for shooting (1440x1080 4:2:2 at 50Hz, 1280x1080 4:2:2 at 60Hz), some may not think this is acceptable.
Some broadcasters may use 1440x1080 for their transmission resolution (UK OTA HD and satellite, France OTA HD, Japan OTA HD I believe) whilst others may mandate 1920x1080 (Sky HD, and US OTA broadcasters)
Whilst the 1920x1080 4:2:2 and 1280x720 4:2:2 interconnects are standards, and there are many broadcast recording, distribution and transmission standards, there are lots of combinations of these, and lots of different bitrate choices that can alter quality to the viewer at home.
And then of course there are the technical standards involved in ensuring decent production values (camera set up and matching, decent camera work, decent sound acquisition etc.) You can shoot with the same kit and have the same distribution model - but deliver totally different qualty results.
Personally I think Sky have very decent technical standards for delivery to the viewer, and a very clean chain. However outside of sport and news they don't actually make much content of their own, so it's difficult to judge their production technical standars. (I sometimes think they over detail-enhance some of their live sports to make it "crisper")
When it comes to great HD production I've seen - I think some of the European HD state broadcasters do a pretty good job. SVT HD (1280x720/50p H264) on Canal Digital usually looks cracking, with no obvious compression artefacts visible, and some of their HD music shows have incredible standards, with very well mixed 5.1 sound at 640kbps and very clean pictures. But then their SD broadcasts on the same platform also usually look excellent, and they've been doing 5.1 sound for SD 16:9 broadcasts for years (it was part of their SD OTA digital standard)