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Offline decoding questions


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#1 HWTest

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Posted 9 December 2018 - 14:21

I have a couple of questions regarding offline decoding.

There is not much about it on the wiki and also searching the forum didn't help.

 

When I watch a decoded recording, it is decoded on the fly but it stays decoded?

 

The decoding delay sets the delay between ECMs?

Because I was testing it with delay set to 7000 and ratelimit set in Oscam and it ignored it and hammered the server very hard, I have no idea why.

When I tested it before with the default delay 1000, I was trying to decode multiple recording at once and the ratelimt in Oscam kicked in.

 

Is it possible to salvage a partially decoded recording using offline decoding?

I have set to always record ECM.

Now when I have a partially decoded recording (say the server was unstable), can I salvage it by setting to 188 1 in the meta file and let it offline decode?

Because when I tested it, the hammering of the server occurred and the decoded parts were still there in the "decoded" recording ...



Re: Offline decoding questions #2 HWTest

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Posted 9 December 2018 - 15:09

I did some more tests.

I've created a partially decoded recording by restarting the server several times during the recording.

(BTW thank you very much for the preconfigured Oscam, it was really very easy to setup.)

Then I changed the meta to 188 1 and started offline decoding.

I watched the Oscam log closely during the decoding and it seems it ignores the delay during decoding of the already decoded parts.

- decoding already decoded parts -> hammering the server with ECMs every second or so

- decoding undecoded parts -> ECM every 7 seconds as setup

 

The decoded recording is fine this time.

Why does it ignore the decoding delay, when decoding already decoded parts?

Why does it ignore the Oscam ratelimit setting?

What can I do to fix it? I'm afraid, that my card goes into punishment, as mentioned here in the forum.

It didn't happen so far but ...



Re: Offline decoding questions #3 Erik Slagter

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Posted 10 December 2018 - 09:30

The disadvantage of setting "always record ECM" is that that is a signal to enigma that the file still needs to be descrambled. That means enigma will always try to get cw's from ecm's for that file, even if it's already completely clear. That might upset you subscriber card.

 

There isn't much documentation on this subject as it doesn't work really well on many receivers (due to driver of hardware limitations).


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* Ziggo digital cable TV (FTA)
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Re: Offline decoding questions #4 HWTest

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Posted 10 December 2018 - 09:46

That seems to be solved by the 188 1 and 188 0 flag in the meta file.

When the flag was set to 188 0 and I started offline decoding, it didn't work, no ECM request sent. I had to change it to 188 1.



Re: Offline decoding questions #5 littlesat

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Posted 10 December 2018 - 10:15

First I think we need to arrange that recording with ECM will be the new default... I know the recordings will be slightly bigger, but when a recording is somehow partly encrypted you still be able to encrypt it afterwards (e.g. in case the softcam and/or CI was shortly offline).


Edited by littlesat, 10 December 2018 - 10:16.

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Re: Offline decoding questions #6 HWTest

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Posted 10 December 2018 - 10:29

There is an option for that (always record ECM) - you mean, that the new default of this option is, to be on?

 

I think the ECM timing issue I've encountered is a problem.

Assuming you have a (several hours) long recording, where the end (say the last 5 minutes) is coded.

You start offline decoding, the card gets hammered so hard, that when the decoding process reaches the coded part at the end, the card is already in punishment mode ...



Re: Offline decoding questions #7 Erik Slagter

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Posted 10 December 2018 - 13:48

First I think we need to arrange that recording with ECM will be the new default... I know the recordings will be slightly bigger, but when a recording is somehow partly encrypted you still be able to encrypt it afterwards (e.g. in case the softcam and/or CI was shortly offline).

See above (#3) why you don't want that (currently, without other changes).


Edited by Erik Slagter, 10 December 2018 - 13:48.

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Re: Offline decoding questions #8 littlesat

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Posted 10 December 2018 - 17:36

And exactly for this we need some changes.... but are you sure it always set the encrypted flag?

Edited by littlesat, 10 December 2018 - 17:37.

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Re: Offline decoding questions #9 Erik Slagter

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Posted 10 December 2018 - 17:58

That's not the issue. The issue is that when enigma sees ECM packets, it will try to fetch the related control word.


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* Ziggo digital cable TV (FTA)
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Re: Offline decoding questions #10 littlesat

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Posted 10 December 2018 - 18:22

There is a meta file with the recording. When the latest value is 1 the recording is encrypted... when it is 0 the recording is not encrypted... when you record witn ecm what is this value doing?????

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Re: Offline decoding questions #11 Erik Slagter

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Posted 12 December 2018 - 17:47

If you record ECM's, it will be "1".


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Re: Offline decoding questions #12 littlesat

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Posted 12 December 2018 - 20:00

Sjoot... ;)... Sounds for doing offline decoding in a good 'way' it need also a lot of decent cpp work... Just re-record it via an timer to encrypt as it is done now via the UI in MoviePlayer gives me the feeling this is more a work-a-round...


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Re: Offline decoding questions #13 Erik Slagter

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Posted 13 December 2018 - 16:57

The way it is done now (by PieterG) is in a technical way very clean. It uses the existing enigma2 infrastructure and adds only little code. The offline decoding is simply making a recording from a file that is concurrently played. The data is inserted into the demux and immediately retrieved from there. Having the effect that any non-unscrambled packets are still descrambled.

 

For this path, it doesn't matter whether the record is marked as "encrypted" (1) or not (0). AFAIK this flag is only used for playback.

 

Resolving ECM packets into control words and sending them to the descrambler is the task of the softcam. The only way to prevent the softcam from resolving the ECM's is to make sure the service/demux is not mentioned in the CApmt sent to the softcam. AFAIK this is controlled by the flag mentioned above.

 

But you need to also consider that recording with ECM marks the recording as "encrypted" anyway.

 

We may want to try some things here, it may be interesting to have an option to record with ECM but not setting the "encrypted" flag. That way it will play normally without loading the subscriber card. If the recording is "damaged" (i.e. some parts are not descrambled), it will not play correctly. But if you do an "offline decode", it will try repair the scrambled packets, but it will load the subscriber card, so do this only when required.


* Wavefrontier T90 with 28E/23E/19E/13E/9E/4.8E/0.8W/5W via SCR switches 2 x 2 x 6 user bands
* Ziggo digital cable TV (FTA)
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Re: Offline decoding questions #14 HWTest

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Posted 13 December 2018 - 17:36

Sounds very promising :)

 

I'm interested mostly in rescuing "damaged" recordings (but without the card bursting in flames).

Just one addendum - I have set to always record ECM and I just checked a couple of new recordings and all have 188 0.

I'm not 100% sure but I think some of them were additionally explicitly set "descramble and record ECM" in their timer settings - I'm not able to verify it, the timers are already deleted.



Re: Offline decoding questions #15 Erik Slagter

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Posted 13 December 2018 - 17:42

The problem is that ECM's are either always resolved or never. There is (at least currently) no way to only resolve ECM's for packets that are not descrambled. Which severly decreases it's usefulness.


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* Ziggo digital cable TV (FTA)
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Re: Offline decoding questions #16 HWTest

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Posted 13 December 2018 - 17:59

That's not really a problem (but it would be great, no doubt), the problem is the speed.

Single (playback) speed, would be great, adjustable speed even better.

 

I have a couple of ideas but I don't know how useful they are:

 

1) the obvious you already mentioned (that's currently not possible)

 

2) Mark scrambled areas manually (similar to cut marks) and during offline decoding process only the marked areas.

(there is a great software for locating scrambled areas - TSDoctor)

 

3) during regular playback detect scrambled areas, descramble them on the fly and replace the scrambled areas in the original file with the descrambled parts on the fly - I'm afraid technically (almost) impossible ...



Re: Offline decoding questions #17 Erik Slagter

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Posted 13 December 2018 - 20:01

2) would be technically possible, I guess

 

3) technically daunting, that's akin to your previous thought, it would mean 

- processor needs to no only read the file but also check one in 188 bytes for scrambled packets (please note: not all vendors do this right)

- at the time the undescrambled packet is found, the softcam needs to be involved, a new CApmt needs to send, the softcam needs to find out which CAIDS are present, find out which ECM pid to use, fetch the ECM, send it to the reader, get a control word back and program it into the descrambler. By the time you have a valid control word programmed, you're already a minute ahead in the recording.

 

Option 2) is more plausible, but one would have to grow the areas such that a valid control word is always in the demuxer whenever a non-descrambled packet arrives.

 

You could think about a fusion of 2 and 3, making a plugin (+maybe executable) that ploughs through the recording and automatically marks the areas to be recovered.


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* Ziggo digital cable TV (FTA)
I don't read PM -> if you have something to ask or to report, do it in the forum so others can benefit. I don't take freelance jobs.
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Re: Offline decoding questions #18 HWTest

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Posted 13 December 2018 - 20:10

Fusion of 2 and 3 - Yes

And it could, during the ploughing, prepare the needed ECMs (find out which CAIDS are present, find out which ECM pid to use) ...



Re: Offline decoding questions #19 Erik Slagter

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Posted 13 December 2018 - 20:18

Nope, that's the softcam (or CI) it's work. Enigma doesn't do much with ECMs.


* Wavefrontier T90 with 28E/23E/19E/13E/9E/4.8E/0.8W/5W via SCR switches 2 x 2 x 6 user bands
* Ziggo digital cable TV (FTA)
I don't read PM -> if you have something to ask or to report, do it in the forum so others can benefit. I don't take freelance jobs.
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Re: Offline decoding questions #20 HWTest

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Posted 13 December 2018 - 20:21

Aha, OK.

 

And thank you for your patience :)






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