Freeview+, "accurate recording", padding, etc.

Remember that digital transmission is really (in simple terms) just a
stream of data, and in the data stream sent with each multiplex, is a
"road map" called Service Information (SI). There is much data here to
help the receiver deal with digital TV; one such "table" contains what I
call the "Start of Programme" (SoP) flag. This can be seen as a simple
toggle, when it changes state the next programme has started. PVRs use
this to start recordings. The SI also contains a table called the Event
Present/Following (EITpf) which provides what's also known as the Now &
Next. That's what you get when you press the "i" button. This EITpf
contains very precise timings for each programme.

The Humax 9200 was designed by a software team who only took the toggle
to indicate the programme start. Sony, for instance, also use the EITpf
start and stop times as a default. How sensible this approach is is
often demonstrated when one of the lesser broadcasters cocks it up.

Most of the major broadcasters send all the right information in the
right order. some don't get the order right, some don't even send it.

Using the Humax "Accurate Record" feature usually works on models later
than the 9200, cause Humax realised (were told) of their error and
designed a more robust system. But every so often some broadcaster
fails......

And don't forget that broadcasters may time the SoP flag to include a
few ads, including the BBC. This is not just to force you to watch an
ad it is useful to allow for the fact that the data sent in the EITpf is
only sent every few seconds.

Someone may well be along soon to more correctly state things.

Richard

Scott wrote:

I thought there were two different systems with the more accurate
system used by the newer equipment. Can any of the experts enlighten
us?

That's my understanding, too. Let's hope an expert comes along...

--
SteveT

"Dickie Mint" wrote in message
...
Remember that digital transmission is really (in simple terms) just a
stream of data, and in the data stream sent with each multiplex, is a
"road map" called Service Information (SI). There is much data here to
help the receiver deal with digital TV; one such "table" contains what I
call the "Start of Programme" (SoP) flag. This can be seen as a simple
toggle, when it changes state the next programme has started. PVRs use
this to start recordings. The SI also contains a table called the Event
Present/Following (EITpf) which provides what's also known as the Now &
Next. That's what you get when you press the "i" button. This EITpf
contains very precise timings for each programme.

Surely it has to be more that a "toggle".

It has to include the name of the program.

Take the case of programs running 10 minutes late and the one before yours
only being 5 minutes long.

The box would start to look for the start signal on time (or perhaps some
time early), see the first toggle and think your program had started and
record it. See the real start signal, think your program had finished and
stop recording.

Only a bunch of idiots would think that this would work?

And out of interest, where are these signals. Are they only in the mux that
they channel is in or are they in all muxes (or somewhere else).

If a box is recording programs on Mux 1 and 2, how does it look for start
signal for a program on mux 3? (or A, B and C)

tim

On Sun, 09 Oct 2011 08:48:11 +0100, tim....
wrote:


"Roger Mills" wrote in message
...
Can someone please enlighten me!

In the user manual for my Humax HDR-Fox T2, under the heading "Freeview+
HD" it describes a process - seemingly equivalent to PDC on an analog
VCR - whereby the start and end times of a scheduled recording are
automatically adjusted if the programme runs early or late.

In the same section, it talks about Series Link, Alternate Instances and
Split Recordings - and goes on to say that not all features are
available
on all channels.

In the menu system, there is a facility to add "padding" to all
recordings
so as not to miss anything if a programme runs early or late. I
currently
have this set to 2 minutes at the start and 10 minutes at the end. This
means that if I want to record two consecutive programmes on the same
channel, the two recordings need to overlap by 12 minutes - and the poor
thing holds up its hands in horror and says "Which do you want to do - I
can't do both?!"

So, a few questions . . .

1. Does this Freeview+ PDC-like feature only apply to HD, or is it on SD
also? [The Humax manual is unclear on this point]

2. If it also applies to SD, which channels is it on / not on?

It theoretically works on all channels, though some are not as good at
sending the signals as they should be.


3. How reliable is it - can I safely remove my padding, and allow it to
do
its own thing?

When recoding one program in isolation it's about as close to 100%
reliable
as you could expect it to get.

But when recording back to back programs there is always going to have
to be
a strategy to resolve conflicts.

IMHO the Hummy takes the wrong view on this, but that's just MHO and
others
don't agree with it. You'll have to for your own


4. Since it can record two channels at once, why can't the stupid thing
make overlapping recordings from the *same* channel if necessary?

Because it can't!


This is why I still prefer to use my PC to record TV programs in spite of
the extra complications in calculating the total run time when using the
basic software (DTVR) supplied with the DVB-T adapter.

I can (and do) schedule a whole string of back to back programs by the
simple expedient of setting the start time less the 2 or 2.5 or 3 minutes
padding required for BBC3 & 4, BBC2 and BBC1 respectively, and the total
run time plus a padding out of 6, 7 or 8 minutes (BBC3 &4, BBC2 and BBC1
respectively). I can then slice and dice the separate programs out of the
single large file thus created using basic (free) video editing software.

The record scheduling software knows nothing of start and stop flags so I
can't reliably[1] handle programs that supposedly immediately follow a
previous one on a different channel. To overcome this, I keep a laptop
with a USB DVB-T tuner running 24/7 to resolve such record scheduling
conflicts.

Unfortunately, even sticking to just BBC broadcast content, I'm sometimes
faced with a 3 way conflict where there exists no repeat option to save
the day. If I deem all three programs to be sufficiently important as to
not be missed, I can usually make use of the XYL's Toppy to capture the
shortest or most disposable of the three[2].

The Toppy has never suffered the issues with transferring files over the
USB link that have been described by Humax owners. The only 'Gotcha'
that's caught me out has been the issue of invalid characters in the file
names used by the Toppy's file system. The transfer proceeds as per usual
but it's only at the end (about 15 minutes per 1 hour program) that it
fails with no obvious error message to indicate why. Once you're aware of
this, it's just a case of renaming the files to eliminate the illegal
characters before proceeding with the transfer.

[1] This is no great loss since, even assuming accurate flagging, the only
(reasonably) certain way to avoid clipping of the start or end of a
program is to use suitable padding. Also, the relationship between
published (in the EPG) start times and the actual start times varies
between the different BBC channels. BBC3 and BBC4 being the most accurate
followed by BBC2 then BBC1.

The general rule followed by the Beeb seems to be "Start 1 minute after
the published time". Unfortunately, there are many instances of exceptions
to this rule with BBC1 being the worst offender in managing every now and
then to not just start exactly on time but the worse sin of starting ahead
of the scheduled time, by as much as two and a half minutes in some cases
(hence the 3 minute start padding).

[2] The shorter program to keep the transfer time to a minimum or most
disposable in case, when previewing from the toppy's archive directly, it
turns out to be a lot more crapper than I was prepared to tolerate as a
'Keepsake'.

--
Regards JB Good

On 09/10/2011 13:35, tim.... wrote:

Surely it has to be more that a "toggle".

It has to include the name of the program.

Take the case of programs running 10 minutes late and the one before yours
only being 5 minutes long.

The box would start to look for the start signal on time (or perhaps some
time early), see the first toggle and think your program had started and
record it. See the real start signal, think your program had finished and
stop recording.

Only a bunch of idiots would think that this would work?

And out of interest, where are these signals. Are they only in the mux that
they channel is in or are they in all muxes (or somewhere else).

If a box is recording programs on Mux 1 and 2, how does it look for start
signal for a program on mux 3? (or A, B and C)


The "toggle" is the last point of action for the PVR, it having derived
all the programme information it needs from the various tables in the
SI. A programme is known to the system as an "event". The EPG is the
human interface to enable the user to see what's on in an easily
understandable form. When you see the programme you want to record the
PVR or STB translates that to the event number.

Each mux's SI contains such information from other muxes as is
necessary, EITpf (actual) in the mux you're using. EITpf in other muxes
known as EITpf(other)for example. A Network Information Table in the SI
tells the PVR (or STB) of all available muxes at that transmitter.

Richard

On Sun, 09 Oct 2011 11:49:22 +0100, Dickie Mint
wrote:

Using the Humax "Accurate Record" feature usually works on models later
than the 9200, cause Humax realised (were told) of their error and
designed a more robust system. But every so often some broadcaster
fails......

My 9300 still occasionally misses the beginning of a programme, even
when nothing was being recorded immediately before.
--
(\__/) M.
(='.'=) Due to the amount of spam posted via googlegroups and
(")_(") their inaction to the problem. I am blocking some articles
posted from there. If you wish your postings to be seen by
everyone you will need use a different method of posting.

On Oct 9, 11:49*am, Dickie Mint
wrote:
Remember that digital transmission is really (in simple terms) just a
stream of data, and in the data stream sent with each multiplex, is a
"road map" called Service Information (SI). *There is much data here to
help the receiver deal with digital TV; one such "table" contains what I
call the "Start of Programme" (SoP) flag. *This can be seen as a simple
toggle, when it changes state the next programme has started. *PVRs use
this to start recordings. *The SI also contains a table called the Event
Present/Following (EITpf) which provides what's also known as the Now &
Next. *That's what you get when you press the "i" button. This EITpf
contains very precise timings for each programme.

Do you have a reference for that "SoP" flag?

I'm well aware of the EITpf transition triggering "accurate"
recording, but I've never heard of SoP and Google isn't helping me.

Cheers,
David.

On 10/10/2011 14:02, wrote:

Do you have a reference for that "SoP" flag?

I'm well aware of the EITpf transition triggering "accurate"
recording, but I've never heard of SoP and Google isn't helping me.

I churned out a load of all that some time ago in these hallowed halls....

It took me ages to ask those who knew and look it up. I'll see if I can
find it again. It's not actually called "start of Programme" I just
coined that phrase to describe what it did. ETSI's anyone?!!

Richard