[mythtv] DVB LiveTV Tuning Blocking / Bug with transform.c

[Jesper Sörensen]

Taylor Jacob wrote:

>I have been trying to get livetv to work with DVB properly.. I am pretty sure I
>have tracked a tuning issue with LiveTV down to dvbdev/transform.c, but I want
>to know if anyone else has seen experienced this or done any debuging with it..
>
>What happens is if you are channel surfing with DVB after a few rapid channel
>changes the card will timeout and immediatly after the 15 Second error message
>you will get the VideoStream/AudioStream messages meaning its starting to fill
>the ringbuffer.. I put some debug code in ReadFromDMX and the data seems to
>start immediatly after the filters are set (as it should), but the transform.c
>code never does anything with it..
>
>This of course never effects scheduled recordings since it takes a few rapid
>channel changes in a row to exhibt this behavior..
>
>Has anyone else noticed this?  I know John Pullan mentioned to me in our
>discussions about the patch effort that he has seen it mentioned on this list
>before and linux-dvb, but I wasn't able to find any postings quickly..
>  
>

I don't know if it's the same bug but several people on the Myth lists 
have reported tuning/zapping problems with DVB. One issue is with 
bad/missing PIDs (causing the backend to hang, unable to retune to a 
working station). I'm also getting the dreaded "Couldn't read data from 
the capture card... Game over." fairly often even on stations with the 
correct PIDs set up, but I don't know what's causing it. Almost all my 
channels are scrambled so it might be a CA problem. Might be a driver 
problem, or something wrong in Myth's tuning code. Sometimes it happens 
directly on startup and it doesn't seem to be caused only by rapid 
zapping but it might of course be related. Anyhow, with your DVB patch 
I'm guessing it will be easier to diagnose and kill any remaining bugs.

>I may not even fix this bug as is, and just remove transform.c along with the
>merging of HDTVRecorder and DVBRecorder since IMO transform.c was crowbared
>into myth.. If I am wrong as to the cause of this please let me know..
>  
>

The less redundant code the better, but I don't know that much about the 
DVB code...

>I wanted to know if anyone else has seen this and what kidns of cards they are
>using.. I have seen it with my happauge Nexus-S and Nova-S.. John mentioned it
>has happened with his Nova-T card..
>  
>

I'm using a Nova-S-CI.

>http://www.digitalregime.com/mythdvb/ <-- Link soon to have a experimental patch
>with new db structure, scanning and auto-pid..
>  
>

Thanks! This looks very promising. I'm looking forward to testing it... :-)

JS