AR quirk ... maybe

[MikeSh]

We've had our new freesat box - the Arris 4K one - for a few months now and it's thrown up an oddity with recording start/end points on back-to-back recordings.
This is most obvious when watching a series where the broadcaster (usually BBC Four in our case) transmits two or more episodes in succession.

We will watch the/an earlier episode right through to the end of the credits and then (usually) stop and delete it. However, when we come to watch the next episode it will start the recording a minute or so before the end of the previous episode (which gives us a moment of deja vu), so we have to skip through the end, credits and interim trailers and babble to get to the actual episode.
It gives the appearance of adding a few minutes padding to the start. (I've not really investigated the end but I think that does usually happen at the start of the next programme, or on some occasions even before the end of the target programme .)

Our old Humax freesat box didn't do this, so I assume it's an Arris thing.
I'm very curious as to how it does it, unless freesat is now sending additional AR codes.

 

[Black Hole]

How sure are you it is using AR at all?

 

[MikeSh]

How sure are you it is using AR at all?

Interesting point. Not very now I think on it.

There's no option in settings to choose timed or ar, so I assumed it would be the latter. But who knows?
OTOH, it has on several occasions missed the last few moments of programmes, so I don't think it has any significant end padding.

It just seems odd that it's recording the same channel twice at the same time. Though with other PVRs I've often found the first few moments of a programme are on the end of the previous one, so it makes sense that it does this if enough capacity is available. I just don't understand how it does it.

 

[Black Hole]

Perhaps there's more knowledge of the Arris in The Other Place.

 

[MikeSh]

Yeah, probably. Not been in there for years. I just threw it out as a curiosity really, though I wonder if SWMBOs Aura does something similar being a later generation device.

 

[Rodders53]

There's an awfully long thread on the freesat 4k box on AVForums where this might have been discussed?
One other place to look is DigitalSpy where an ex-colleague who was the de facto expert on PDC and AR, posts.

Each box/maker will design how they work within the specs for DVB, with possibility for 'interpretation' differences. The Arris box has 4/5 tuner-decoder modules so can easily use two to record the same data stream, rather than relying on using the same tuner-decoder to service both recordings as other designs may do?

I would also wonder if later Freeview 3+ multi-tuner 5000Ts and Auras handle such back to back recordings in a similar (or very different) way?

Personally on BBC FOUR especially I'd not be certain that AR was any different to Clock Time playout of the schedule? So stuff like early cutoff could happen due to playout timing miscalculations.

I recall in the dim and distant past having some b-t-b recordings where the start of the next programme was on the end of the previous (that, having watched, I'd just deleted )... May even have been something like Casualty double bills. Nothing more recent though.

 

[prpr]

I'm very curious as to how it does it, unless freesat is now sending additional AR codes.

You can't have two programmes running at once on DVB on the same service.

I just don't understand how it does it.

Presumably it just copies the same received data to two different files for whatever it deems the duration of the overlap.

 

[prpr]

Personally on BBC FOUR especially I'd not be certain that AR was any different to Clock Time playout of the schedule?

It is. Here's the data for BBC FOUR HD from yesterday:

09/29 00:35:48 Event 18048:22758 4E:23 started 00:35:00 01:00:00 "Life" "/b/BE5EP" "/b/A34EN/14"
09/29 01:34:51 Event 18048:22759 4E:24 started 01:35:00 01:00:00 "Hidden Wales with Will Millard" "/1b/54C7O1" "/1b/549MHN/04"
09/29 02:34:51 Event 18048:22760 4E:25 started 02:35:00 01:55:00 "This is BBC Four" "/m/Z69" ""
09/29 04:30:03 Event 18048:22761 4E:26 started 04:30:00 13:28:00 "This is BBC Four" "" ""
09/29 17:58:23 Event 18048:22792 4E:27 started 17:58:00 00:02:00 "This is BBC Four" "/m/Z69" ""
09/29 17:59:48 Event 18048:22793 4E:28 started 18:00:00 00:30:00 "TOTP: 1995" "/m/YEVH" "/b/3UNHM/04"
09/29 18:29:38 Event 18048:22794 4E:29 started 18:30:00 00:30:00 "TOTP: 1995" "/m/YEVM" "/b/3UNHM/04"
09/29 18:59:36 Event 18048:22795 4E:30 started 19:00:00 00:30:00 "TOTP: 1991" "/m/K03F" "/b/3UNHM/04"
09/29 19:30:37 Event 18048:22796 4E:31 started 19:30:00 00:30:00 "TOTP: 1977" "/b/SCV0J" "/b/3UNHM/04"
09/29 19:59:09 Event 18048:22797 4E:00 started 20:00:00 01:00:00 "Phil Collins at the BBC" "/m/HXNQ" ""
09/29 21:00:02 Event 18048:22798 4E:01 started 21:00:00 00:40:00 "Genesis: Old Grey Whistle Test" "/m/R5V2" "/b/3U503"
09/29 21:40:01 Event 18048:22799 4E:02 started 21:40:00 00:45:00 "TOTP2: Genesis" "/b/26A6SC" "/b/3SMM2/04"
09/29 22:26:14 Event 18048:22800 4E:03 started 22:25:00 01:00:00 "Mark Lawson Talks to... Phil..." "/b/7UJNA" "/b/3N8E3"
09/29 23:25:14 Event 18048:22801 4E:04 started 23:25:00 00:30:00 "TOTP: 1991" "/m/K03F" "/b/3UNHM/14"
09/29 23:56:01 Event 18048:22802 4E:05 started 23:55:00 00:30:00 "TOTP: 1977" "/b/SCV0J" "/b/3UNHM/04"

Compare the actual start with the scheduled start.

 

[MikeSh]

I recall in the dim and distant past having some b-t-b recordings where the start of the next programme was on the end of the previous (that, having watched, I'd just deleted )

Yep. Very common with our previous freesat box (1010S). As a result I was in the habit of always FFing the recording to the end to check it before deleting.
Annoyingly, in many cases although the beginning of the next programme was not on the previous recording the start was still clipped by a few seconds. Presumably the box took a little while to switch over when the AR flag was sent. At least we don't have that problem any more

 

[MikeSh]

Presumably it just copies the same received data to two different files for whatever it deems the duration of the overlap.

Yes. And if the overlap was on the end of the previous programme that would be easy. But adding it to the front of the next one, ie. before the AR flag occurs, is less so. I actually wonder if when it has two consecutive programmes it operates a kind of live buffer of a few minutes for the second one, like you can use the buffer on a FOX to record stuff that's already passed.

I might go and have a look on AVR and/or DS sometime. I'm on holiday shortly and will probably have lots of time to kill.

 

[Black Hole]

I actually wonder if when it has two consecutive programmes it operates a kind of live buffer of a few minutes for the second one

Yes, some kind of circular buffer of a few minutes to capture a window ahead of the trigger (rather like a dashcam) seems like a good idea, and mitigates the broadcaster being late with their AR flags. If that extends past the end of a recording also, so much the better (mitigating early cut-off), but no buffer necessary for that.