[mythtv-users] Graphic cards supporting VDPAU and sound over HDMI

[mythtv at derdev.com]

On Tue, 30 Mar 2010 11:46:17 +0100, Andre <mythtv-list at dinkum.org.uk>
wrote:
> On 30 Mar 2010, at 11:18, Christopher Kerr wrote:
>> 
>> Actually, that reminds me of something I've been wondering about for a
>> while: why do we use 1080i anyway? Basically all HD displays are
>> progressive by nature, and it takes the same amount of bandwidth to
>> broadcast 1080i50 as 1080p25. So why do they do it that way? Doesn't
>> MPEG-2 encoding work more efficiently on progressive content, anyhow?
> 
> 
> Yes, yes and yes!
> 
> When HD first started commercially (theoretically it's 20+ years old
> already) in the US you could buy 720p60 and 1080i30 equipment. In Europe
> only 1080i25 for many years, even now lots of equipment needs firmware
> updates to work properly with 720p50 or doesn't ever work properly!  So
in
> the US there are some stations that transmit 720p and some sports events
> are shot in 720p, no-one would shoot anything live in 1080p25 or
1080p30,
> it would look truly awful. Drama and other shows where everything can be
> controlled very thoroughly especially the camera movements often shoot
in
> 1080p25 or 1080p24, actually more often 2k24 or on film.
> 
> It's pretty much impossible to change a TV station from 720p50 to
1080i25
> or 1080p25 between programmes, on outside broadcasts it can take a day
to
> switch everything over in just one truck. So 1080i25 gives a compromise
> between ok 1080p25 for movies and 1080i25 for live sports without
changing
> anything. Some transmission encoders will detect 1080p25 shows in a
1080i25
> feed, de-interlace and transmit 1080p25. Just search the lists here for
> people having trouble with "progressive flag" video playback in MythTV.
> 
> Things are changing though an EBU lecture yesterday referred to
interlaced
> video as "legacy HD", all the new HD standards do not permit interlaced
> video :-))
> 
> Most broadcast engineers don't really understand compressed video, very
> few understand that 720p actually has slightly higher detail than 1080i,
> very very few will believe your assertion that 1080p25 takes the same
> bandwidth as 1080i25 (in fact it needs less) the administrators are
worse
> and most of the viewers have no concept! Many many stations launch with
> 1080i because the numbers are bigger and that's what our viewers want, I
> hear this so much of the time.
> 
> When broadcast TV stations talk about 1080p they usually mean 1080p50 or
> 1080p60, equipment to do this is currently very expensive, and almost
> no-one knows how to work with it. In time it will come, it looks utterly
> gorgeous and doesn't need any more transmission bandwidth than 1080i25,
in
> many cases it uses less, try finding a broadcast engineer that believes
> that!
> 
> Sorry too much information ;-)
> 
> Andre


Andre, a personal thanks, that was a pretty cool writeup.