[mythtv] CAM reset needed

Rudy Zijlstra mythtv at edsons.demon.nl
Sun Jan 21 12:25:04 UTC 2007

Wim Fokkens wrote:

>>>I'm finding that after using the CAM in a recording for about 1 hour or
>>>more, i appear to need to reset the CAM. I've seen some strange
>>>behaviour in tha past days and started testing yesterday and today. Each
>>>time the what i see is that after watching an encrypted channel for a
>>>while (seems to be >1hour), changing to another channel results in no
>>>decryption (status LMSc in stead of LMSC). Each time this happens, if i
>>>restart the backend the problem is solved and decryption works again.
>>>Would it be an idea to reset the CAM after each recording / before each
>>I still have similar problems, although it has improved recently
>>(running 12465), I sometimes have to restart the backend to get cam
>>working, while its not the best solution the option to completely
>>reset the cam on channel change would be a huge improvement!
>>I tried to make a patch to do it but I didnt get very far :(
>I think it would be smarter to program some kind of watchdog for the CAM.
>Witch resets the cam when the cam is not responding properly instead on each
>channel change (the last option would make channel changes unnecessary slow)
So far, i've only seen it misbehave on channel change. I've not seen it 
fail once decryption is ongoing. I would prefer a slower channel change 
on encrypted DVB channels above failing tunes. I also prefer predictable 
timings above non-predictable. On the other hand, many of the 
unexpectatly slow changes would not be visible (would not be in live-TV. 
As far as i currently know, it only fails on channel change (start of 
encryption), so it would not matter so much.

On the other hand, how to detect malbehaviour? In other words, how to 
detect the difference between "i need a reset" and "you have no rights 
for this". It seems the CAM can give messages to the last effect, i 
simply do not know enough about it. One thing i do  not know for 
example, is to which level the different CAM's are standardised in their 
error messages. I do know that not all CAM's work in all STB's, which 
seems to point to the fact they are not all the same in behaviour.

It is those uncertainties, and the lack of documentation on CAM's, that 
lead me to the first line approach of CAM reset at channel change.

As i am no programmer though, I can discuss, yet not generate a patch. 
Will happily test patches though.



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