Any chance of 1080p25 on BBC HD on Freesat
Since this has been testing on Freeview HD, I was just wondering if this is viable on Freesat - considering there are 2 BBC HD streams (one of which could be used for Sky and the other for Freesat if that becomes an issue). I was wondering if Freesat boxes support it...
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Not completely sure about freesat boxes but it shouldn't be a problem, it is also down to the TV but most modern ones should be able to deal with it ok.
I was going to try to determine if it was by examining the pictures when I knew HD on Freeview was 1080p25 (NB I have a Freesat/Freeview HD TV) - but I decided that it was getting a bit too much! My understanding is that -p25 modes are a standard part of the DVB specs (like static video) - reslfj?
DVB-T2 HD uses MBAFF to give 1080p25 as appropriate - and receivers will flag this in different ways depending on design.
PS I think you can easily see the difference in the lack of motion blur.
No they have not, all broadcast HD TV in the UK is 1080i two fields of 1/50 sec making one full frame every 1/25 sec. If the footage is derived from a single static frame like a frame of film because there is no movement between the two fields it's effectively a progressive picture, it's still transmitted as two interlaced fields. The only truly progressive broadcast source is 720p 1280 x 720 at 50fps but apart from VOD services no-one uses 720p.
Of course (virtually) any deinterlacer will effectively give 1080p25 from a 24/25fps original broadcast as 1080i25 - in fact zero processing will give it (like 24/25fps films shown on analogue)
Which is all that the BBC are doing.
Take a 1080p25 source and put it inside a 1080i50 stream, which the TV recognises and treats as such.
See http://www.avforums.com/forums/6009712-post2.html regarding Sky
and an explanation on wikipedia
Obviously for UK read 25/50 instead of 24/60
Sky don't transmit 1080p50, but 1080p25 in a 1080i50 stream, exactly as the BBC is now doing on Freeview HD.
How else do you think the BBC are now transmitting 1080p25 using existing equipment and receivers?
Actually the BBC might be doing it differently as I understand Freeview HD boxes do have a 1080p output which sky boxes do not.
But the above is what sky do.
you have just made an assumption based on your lack of understanding of mpeg4 H.264 encoding.
What you are missing is that Mpeg4 H.264 in the modes used by sky and the BBC Avoid encoding interlaced ether by frame or by macro-block depending on the mode used. Encoding interlaced video is inefficient and requires a higher bitrate to achieve an expectable picture quality. Thus the these mode where added to encode progressively whenever it is possible as a bandwidth saving measure.
The result is that all film based or 25p sources are encoded and broadcast as 1080p25 , it's flagged as an interlaced stream and it is your STB that re interlaces this before sending it to your TV.
as someone else mentioned with logs, Interlaced material can end up being encoded with odd average frame rates between 25-50fps as the encoder finds frames that do not require interlacing and encodes them as such
25P gives slightly better picture than current offering but 50i handles motion better so horses for courses.
My understanding is 50P offers the best of both worlds but needs far more bandwidth (I think it may even be double) and compatible tv's.
Not interlaced 50 progressive.
I understand most tv's can't show 50P because they lack the necessary processing power to handle 50 Progressive frames per second.
The problem with wrapping 1080p25 in a 1080i50 stream is that the chroma sub-sampling is lower resolution (based on fields, rather than frames), some encoders don't always adapt properly (e.g. using quantisation matrices which are less than ideal, or picking field encoding due to combing-like content in the video, or just being stupid), and the true nature of the video might not always be correctly detected in the end.
Other than those issues, there is no inherent problem with encoding full "progressive" frames in 1080i50 mode - this feature exists because that's just a (momentary) still picture, and there are plenty of those in genuine interlaced content too.
Cheers,
David.
1280x720p50 has been there all the time, as has 720x576p50 - that's even handled by some old 100Hz CRTs.
It's not the frame rate that's the problem - it's the total data rate, and having an input that supports it.
Cheers,
David.
http://www.bbc.co.uk/blogs/researchanddevelopment/
None taken.
2Bdecided would be a good person to comment as he knows what he is talking about.
Agreed. You have twice as much as data to process with 50P vs 50i and thats what many tv's can't handle.
50P and even 100i is the Holy Grail of TV but like many technologies there's just no push towards widespread adoption because broadcasters just see increased bandwdith costs and tv manufacturers see little demand in the absence of 50P broadcasts.
Now thats very interesting. But how does this affect Freesat?
It doesn't sound like it.
As stated in the BBC Blog about this, a Freeview HD spec box output is mandated to output 1080P, Freesat isn't.
Are we going to be able to see the difference, time will tell.
But that doesn't mean that the BBC might encode Freesat transmissions as 1080p25 as described above as Sky does, and leave the TV to handle it, rather than handling it in the Freeview HD box.
What people see on the screen should just be the same - differences in the quality of the decoding aside...
http://www.linowsat.de/cgi-bin/lsat.cgi?0282-10847-V-2050-0-0
So how does that help ?