BBC HDTV on Freeview idea

The most empty BBC DTT mux is Mux B:

http://www.dtg.org.uk/retailer/dtt_channels.html#muxb

BBC FOUR / CBeebies
BBC PARLIAMENT
The Community Channel (6am to 9am only)
301 BBCi
302 BBCi
303 BBCi
1 Xtra BBC
Radio 5 Live
BBC Five Live Sports Extra
BBC 6 Music
BBC 7
BBC Asian Network

The mux capacity is 18.1 Mbps. The radio stations consume 800kbps, but
the stereo stations should use a minimum bit rate of 192kbps per
station, so they require an extra 160kbps, making a total of 960kbps for
radio.

18.1 - 0.96 = 17.14 Mbps

So they've got 17.14 Mbps for

BBC4 / CBeebies
BBC Parliament
BBCi
The Community Channel

Ignoring The Community Channel, because it only transmits between 6am
and 9am and an HDTV channel doesn't need to be 24-hour.

If we assume the BBC buys new MPEG-2 video encoders / stat-muxer like
the ones used on the commercial multiplexes, and that an HDTV channel
requires an average bit rate of 8 Mbps, then:

Option 1:

Only provide an HDTV stream when the part-time BBCi stream is not
running:

The 17.14 Mbps could be allocated as follows:

8 Mbps for video + 192kbps (AAC) for audio for an HDTV stream

You've then got 17.14 - 8.192 = 8.948 Mbps for:

BBC4 / CBeebies
BBC Parliament
2 x BBC News multiscreens

They could then use:

4Mbps for video + 256kbps for audio for BBC4/CBeebies
1.5Mbps for video + 192kbps for audio for each quarter-screen channel
(BBC Parliament + 2 x news multiscreens)

When you consider that C4 typically uses between 2.5Mbps and 3Mbps, and
some of the newer channels use about 2.0 to 2.5Mbps on average, 4Mbps
for BBC4 and 1.5Mbps for quarter-screens are both more than enough.


Option 2:

Provide an HDTV stream as well as running the part-time BBCi streams.
This would only rarely be an issue anyway, because the BBCi streams are
rarely utilised.

Same as above but use on average 2 Mbps for the video + 192kbps for the
audio for the BBCi stream, leaving

8.948 - 2.192 = 6.756 Mbps

allocated as follows:

3Mbps for video + 256kbps for audio for BBC4/CBeebies

1Mbps for video + 160kbps for audio for each of the 3 quarter-screen
channels

As I say, this is only an issue when the BBCi stream is in use, so at
all other times they can revert back to Option 1 bit rates.

Sorted. Will they do it? I doubt it; it's the BBC, and they move about
as quickly as your average supertanker.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview & DAB prices:
http://www.digitalradiotech.co.uk/fr..._receivers.htm
http://www.digitalradiotech.co.uk/dab_radios.htm

DAB sounds worse than FM wrote:
The most empty BBC DTT mux is Mux B:

Oh dear.

I understand the BBC are to use a different, experimental, multiplex.

"Calm down, dear."

Raoul.

Sorted. Will they do it? I doubt it; it's the BBC, and they move about as
quickly as your average supertanker.

Steve I once had a supertanker bearing down on me and I had seawater in my
diesel. Believe me a supertanker is not a good example of a slow thing.

Bill

"DAB sounds worse than FM" wrote in message
...


8 Mbps for video + 192kbps (AAC) for audio for an HDTV stream


From what I have seen you need at least 12mbit/s for Video and because
broadcast quality H264 coders are very much in their infancy you might have
to start with 15mbit/s or you will be changing your tag to "HD looks worse
than analogue".

Your sums miss out all the interesting detail like AD, subtitles, MHEG5
applications, cross carried SI, SI for the actuals, PSI and mux overhead.

I'm applaud that someone who campains so hard against low audio bitrates
that would consider squeezing the videos like that.

I also think time sharing an HD trial service with 301/302 will cause
problems. They are going to want to show off their premium productions and
I'm sure that this will include important sporting events like the World Cup
or Wimbledon and events like the last night of the Proms, when they need
301/302.

Glyn

Bill Wright wrote:
Sorted. Will they do it? I doubt it; it's the BBC, and they move
about as quickly as your average supertanker.

Steve I once had a supertanker bearing down on me and I had seawater
in my diesel. Believe me a supertanker is not a good example of a
slow thing.


True. Thinking about it, I was probably thinking about a supertanker
doing a U-turn, but that's a bad analogy in this case.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview & DAB prices:
http://www.digitalradiotech.co.uk/fr..._receivers.htm
http://www.digitalradiotech.co.uk/dab_radios.htm

GlynM wrote:
"DAB sounds worse than FM" wrote in message
...


8 Mbps for video + 192kbps (AAC) for audio for an HDTV stream


From what I have seen you need at least 12mbit/s for Video


If that's correct then fair enough. I have read articles (can't remember
which or where) that said that H.264 can be used at 8 Mbps for video.


and because
broadcast quality H264 coders are very much in their infancy you
might have to start with 15mbit/s or you will be changing your tag to
"HD looks worse than analogue".

Your sums miss out all the interesting detail like AD, subtitles,
MHEG5 applications, cross carried SI, SI for the actuals, PSI and mux
overhead.


True, but if you used Option 1, and if 8Mbps was used (i.e. HDTV stream
not used at the same time as the BBCi stream) then there's plenty of
headroom (i.e. you can eat into the bit rates of the main streams
slightly).


I'm applaud that someone who campains so hard against low audio
bitrates that would consider squeezing the videos like that.


If you're talking about the BBC4, BBC Parliament and BBC News
multiscreens, then they're not using these encoders that are tuned for
lower bit rates. If new encoders were bought then I think the following
bit rates would be acceptable:

4Mbps for video + 256kbps for audio for BBC4/CBeebies
1.5Mbps for video + 192kbps for audio for each quarter-screen channel
(BBC Parliament + 2 x news multiscreens)

Just look at the bloody commercial TV channel bit rates. Some are using
2 Mbps, and I'm suggesting that BBC4 use TWICE that much, and
QUARTER-SCREEN channels should use almost as much.

Basically, it's about trying to make HDTV available on Freeview. IMO,
it's worth slightly degrading the picture quality on BBC4 (who cares
about the picture quality of BBC news multiscreens, or the BBCi video
streams that are watched at any one time by an audience that consists of
3 men, 2 dogs, a cat and a budgie).

You know, you lectured me once about "broadcasting is a trade-off blah
blah". What I've just come up with is just such a trade-off -- allowing
an HDTV channel to be transmitted by slightly reducing the picture
quality of BBC4. If current H.264 video encoders can't provide decent
quality HD at 8Mbps then fair enough. But at least I've tried. And
what's the alternative? Waiting for analogue switchoff? That's 7 years
away for you lot in the south east. Is it desirable to wait that long?
Nope.

And anyway, I don't see how someone from the BBC has the balls to have a
go at me about broadcast quality. Only today I received a letter from
Reception Advice after I'd written to the DG, and it consisted of a page
full of patronising bull**** about DAB which I've seen time and again
(and changing bit rates on DAB wasn't even the subject of the letter,
although that's what the reply was mainly about), and it highlighted the
fact that the BBC doesn't seem to have the faintest idea how to get the
most out of the resources at its disposal. So, don't lecture me about
quality. You can lecture me about quality once the BBC provide their
radio stations at a higher audio quality than on FM on at least once
digital platform. Until then, don't even think about it until you work
for someone else.


I also think time sharing an HD trial service with 301/302 will cause
problems. They are going to want to show off their premium
productions and I'm sure that this will include important sporting
events like the World Cup or Wimbledon and events like the last night
of the Proms, when they need 301/302.


Well, it was an idea. Looks like Freeview will have to wait until
2009-2012 for HD then, eh. Great stuff.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview & DAB prices:
http://www.digitalradiotech.co.uk/fr..._receivers.htm
http://www.digitalradiotech.co.uk/dab_radios.htm

"DAB sounds worse than FM" wrote in message
...

Just look at the bloody commercial TV channel bit rates. Some are using 2
Mbps, ...

And they often look crap.


and I'm suggesting that BBC4 use TWICE that much, and QUARTER-SCREEN
channels should use almost as much.


Trouble is that when 301/302 have moving pictures BBC4 is getting less than
that already.

A quick look at muxB on CP shows 4 videos (remember that the news multi
screens and Parliament are all contained inside one full resolution video).
The video bundle is about 14mbit/s, that's 3.5Mbit/s per service. The rest
of the bitrate is being used by the audios and all those interesting details
and remember that the new coders on the commercial muxes are heavily reliant
on stat-muxing and stat-muxing only works if you have multiple, diverse,
services. It won't work with just two services unless you want to try and
sat-mux them with the HD. Now that would be really fun.


Basically, it's about trying to make HDTV available on Freeview. IMO, it's
worth slightly degrading the picture quality on BBC4 (who cares about the
picture quality of BBC news multiscreens, or the BBCi video streams that
are watched at any one time by an audience that consists of 3 men, 2 dogs,
a cat and a budgie).

But there are around 650 very influential views of Parliament.


You know, you lectured me once about "broadcasting is a trade-off blah
blah". What I've just come up with is just such a trade-off -- allowing an
HDTV channel to be transmitted by slightly reducing the picture quality of
BBC4. If current H.264 video encoders can't provide decent quality HD at
8Mbps then fair enough. But at least I've tried. And what's the
alternative? Waiting for analogue switchoff? That's 7 years away for you
lot in the south east. Is it desirable to wait that long? Nope.

There is always DSAT.

... Until then, don't even think about it until you work for someone
else.

Don't think it will be long. 50/50 that I'm on the redundancy list in the
new year. Who needs engineers anyway?

Glyn

GlynM wrote:
"DAB sounds worse than FM" wrote in message
...

Just look at the bloody commercial TV channel bit rates. Some are
using 2 Mbps, ...

And they often look crap.


I know they do, but I'm recommending that BBC4 should use TWICE that bit
rate!


and I'm suggesting that BBC4 use TWICE that much, and QUARTER-SCREEN
channels should use almost as much.


Trouble is that when 301/302 have moving pictures BBC4 is getting
less than that already.


But Option 1 assumes that 301/302 aren't carrying moving pictures.


A quick look at muxB on CP shows 4 videos (remember that the news
multi screens and Parliament are all contained inside one full
resolution video). The video bundle is about 14mbit/s, that's
3.5Mbit/s per service.


Eh? There's TWO news multiscreens and Parliament. That's 3 services.
There's also 301/302. Are you including the still images that consume
about 3.5Mbps in the bit rate?


The rest of the bitrate is being used by the
audios and all those interesting details and remember that the new
coders on the commercial muxes are heavily reliant on stat-muxing and
stat-muxing only works if you have multiple, diverse, services.


No, it works *better* the more services you have. It still obviously
works with less services.


It won't work with just two services unless you want to try and
sat-mux
them with the HD. Now that would be really fun.


BBC4
BBC news multiscreen 1
BBC news multiscreen 2
BBC Parliament
HDTV channel

5 services. Not 2. You'd just have to set it up with the appropriate max
and min bit rate values for each service. Will it be perfect? Nope. Is
it better than waiting until 2012? Yep.


Basically, it's about trying to make HDTV available on Freeview.
IMO, it's worth slightly degrading the picture quality on BBC4 (who
cares about the picture quality of BBC news multiscreens, or the
BBCi video streams that are watched at any one time by an audience
that consists of 3 men, 2 dogs, a cat and a budgie).

But there are around 650 very influential views of Parliament.


That'd just about sum up the BBC's attitude towards providing quality:
provide it for posh people and influential people, and screw the plebs.


You know, you lectured me once about "broadcasting is a trade-off
blah blah". What I've just come up with is just such a trade-off --
allowing an HDTV channel to be transmitted by slightly reducing the
picture quality of BBC4. If current H.264 video encoders can't
provide decent quality HD at 8Mbps then fair enough. But at least
I've tried. And what's the alternative? Waiting for analogue
switchoff? That's 7 years away for you lot in the south east. Is it
desirable to wait that long? Nope.

There is always DSAT.


Yes. And if they provide HDTV on cable and satellite but not on Freeview
then I'm looking forward to seeing them justify their use of
insufficient bit rates levels for the radio stations on the digital TV
platforms (which up to now they've tried to justify using the argument
that it maintains platform neutrality -- i.e. not increasing the bit
rates on the digital TV platforms makes the audio quality closer to the
abysmal audio quality of their stations on DAB).


... Until then, don't even think about it until you work for someone
else.

Don't think it will be long. 50/50 that I'm on the redundancy list in
the new year.


Well, then you will be able to have a go at me. ;-)


Who needs engineers anyway?


I think they're recruiting heavily in China at the moment. ;-)


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview & DAB prices:
http://www.digitalradiotech.co.uk/fr..._receivers.htm
http://www.digitalradiotech.co.uk/dab_radios.htm

"DAB sounds worse than FM" wrote in message
...

GlynM wrote:
A quick look at muxB on CP shows 4 videos (remember that the news
multi screens and Parliament are all contained inside one full
resolution video). The video bundle is about 14mbit/s, that's
3.5Mbit/s per service.


Eh? There's TWO news multiscreens and Parliament. That's 3 services.
There's also 301/302. Are you including the still images that consume
about 3.5Mbps in the bit rate?

...
BBC4
BBC news multiscreen 1
BBC news multiscreen 2
BBC Parliament
HDTV channel

5 services. Not 2. You'd just have to set it up with the appropriate max

Please at least read what I have written. "(remember that the news multi
screens and Parliament are all contained inside one full resolution video)".

If that wasn't clear here is a bit more detail: The video for the news
multiscreens and Parliament are matrixed together into a single video. The
BBCi applications apply a mask so that you only see the part of the screen
applicable to that particular application. There are only 4 coders in the
stat-mux:

BBC4/CBeebies
Parliament & multiscreens
301
302

To try and stop STBs from seeing the matrix before the BBCi application get
going the video is hidden by changing its stream type to user private pes
data. The BBCi application then tells the video decoder where to find the
video.

Glyn

"DAB sounds worse than FM" wrote in message
...
The most empty BBC DTT mux is Mux B:

Will existing boxes cope with an unintelligable (to them) MPEG4 stream
within a multiplex?

I have no idea, but could imagine they might crash.

Roger