odr-padenc v2.2.0 and DLS update time

[Nick Piggott]

I updated odr-padenc to v2.2.0.

I'm inserting 24 bytes / frame, and transmitting a slideshow (image = 10299 bytes) and DLS. The sleep time is set to 12 seconds (10299 / 24 * 0.024ms = 10.3 seconds).

The DLS is taking 63 seconds to update following a change to the input text file. In practical terms, it means the first minute or so of a song is showing the details of the previous song, which isn't very good. In the prior version the worst case secenario was a delay of the sleep time (~ 12 seconds).

I know there's been some big changes to 2.2.0 in the way it handles inputs, in order to interleave DLS and Slideshow better, but any ideas on how I can get it to update DLS more promptly? Otherwise I'll need to revert to 2.1.1

Thanks

[Stefan Pöschel]

Hi Nick,

hmm, this should not happen and I currently cannot think of why this
happens. The DLS should use the updated text after the 12 seconds sleep
time as intended - not after 63 seconds.
(BTW the interleaving of DLS and Slideshow was already introduced with
v2.1.0)

Do the 63 seconds fall together with a slideshow image change on the
receiver?
Does the delay still occur with e.g. 15 seconds sleep time?
Which cmdlines do you use for PAD and audio encoder?

Regards,
Stefan

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[Nick Piggott]

Hi,

I've currently got a static slide on there, so I'll need to create a variant version and swap between the two. I'll try that tonight.

The command lines are:

odr-padenc --output /home/dabsys/site/mot/station.mot --dls /home/dabsys/site/mot/station.txt --dir=/home/dabsys/site/mot/slideshow/station --raw-slides --pad=24 --sleep=12

odr-audioenc --dab --bitrate=128 --dabmode=j --dabpsy=2 --pad=24 --pad-fifo=/home/dabsys/site/mot/station.mot --input=/dev/stdin --output=tcp://127.0.0.1:9001

I'll try bumping the sleep time to 15 seconds, in case it is overflowing.

Nick

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[Nick Piggott]

Switching to --sleep=15 has improved it.

How many bytes are allocated to DLS relative to Slideshow in the new method?

My original calcs were *fairly* tight (10299 bytes file, plus MOT overhead (10%) plus 128 bytes DLS = 11.5 seconds). Maybe it was overflowing and filling the buffers?

Nick

[Stefan Pöschel]

It indeed seems that overflow is the reason here:

The PAD size of 24 results in:
- 2 bytes F-PAD, signalling the X-PAD
- (up to) 22 bytes X-PAD

Due to DAB restrictions on the X-PAD Data Group sizes, rather 20-21
bytes can be used for actual Slideshow/DLS payload.

The DLS is inserted every 50 PAD packets during transmission of a slide.
In your case of 48kHz MP2, this corresponds to every 1200ms.

So:
10299 bytes plus assumed 10% overhead....= 11329 bytes.
With 21 bytes usable X-PAD, this results in 539 X-PADs needed.

Every 50th X-PAD DLS is inserted, which takes ~7 X-PADs (assuming 128
bytes plus some overhead). So 43 X-PADs remain for the Slideshow until
the DLS is inserted again.

539 / 43 = 12,5 iterations
12,5 * 50 = 626,7 X-PADs for a single slide pass
626,7 * 0,024 = 15,04s

So 16s should be sufficient in theory, maybe use 17s just to make sure.

Another question is then why the problem did not already occur with v2.1.1.

Regards,
Stefan

Am 06.06.2017 um 17:30 schrieb Nick Piggott:
> Switching to --sleep=15 has improved it.
>
> How many bytes are allocated to DLS relative to Slideshow in the new method?
>
> My original calcs were *fairly* tight (10299 bytes file, plus MOT
> overhead (10%) plus 128 bytes DLS = 11.5 seconds). Maybe it was
> overflowing and filling the buffers?
>
>
> Nick
>
>
> On Tuesday, 6 June 2017 16:10:05 UTC+1, Nick Piggott wrote:
>
> Hi,
>
> I've currently got a static slide on there, so I'll need to create a
> variant version and swap between the two. I'll try that tonight.
>
> The command lines are:
>
> odr-padenc --output /home/dabsys/site/mot/station.mot --dls
> /home/dabsys/site/mot/station.txt
> --dir=/home/dabsys/site/mot/slideshow/station --raw-slides --pad=24
> --sleep=12
> odr-audioenc --dab --bitrate=128 --dabmode=j --dabpsy=2 --pad=24
> --pad-fifo=/home/dabsys/site/mot/station.mot --input=/dev/stdin

> --output=tcp://127.0.0.1:9001 <http://127.0.0.1:9001>

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[Nick Piggott]

Hi Stefan

Thanks for the explanation. So I'm clear, the encoder reserves 50 X-PAD frames, inserts the DLS using as many X-PAD frames as required, and then uses the remaining X-PAD frames to continue transmission of the MOT Slideshow?

I've increased the delay to 17 seconds, and the behaviour is now much better.

I think I actually jumped versions from 2.0.1 to 2.2, so ignore my comment about 2.1!

Thanks

Nick

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[Stefan Pöschel]

Hi Nick,

Am 06.06.2017 um 18:39 schrieb Nick Piggott:
> Thanks for the explanation. So I'm clear, the encoder reserves 50 X-PAD
> frames, inserts the DLS using as many X-PAD frames as required, and then
> uses the remaining X-PAD frames to continue transmission of the MOT
> Slideshow?

Yes, kind of - it is rather a continuous process than a reservation of
X-PADs. The exact procedure is:

The PAD encoder maintains an internal FIFO queue with the DLSs/slides to
be processed. The queue is processed in order and usually contains just
the current slide. So usually a slide is processed.
Now every 50th X-PAD, a new DLS is inserted at the front of the queue.
That DLS is then processed completely until the (temporarily
interrupted) processing of the slide is resumed.
(In addition, after a slide a final DLS is inserted.)

> I've increased the delay to 17 seconds, and the behaviour is now much
> better.

Great!

> I think I actually jumped versions from 2.0.1 to 2.2, so ignore my
> comment about 2.1!

Ah, that explains quite a bit.

Regards,
Stefan

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[Jeffrey MacK]

Hi Nick,

Do you know if it possible to send with PadEnc a preset logo like the German stations?

Or is there a option that the current logo 320x240 resize to a preset logo's ?

Regards,

Jeffrey

[Nick Piggott]

Hello Jeffrey,

If you're talking about the radio station logos that are shown in some cars (for example VW, Seat) on the presets, then these are "burned" into the car and cannot be updated over the air. The only update methods are for the driver to take their car back to an official dealership and have a software update performed, or download the logos from the manufacturers website and update them individually. Many of the logos on the manufacturer's website are out of date.

Nick