[mythtv] Suggestion for improving SLOW channel changing inLiveTV.....

Ed W lists at wildgooses.com
Sun Sep 11 14:02:12 UTC 2005

>I'd appreciate your reply to my questions below.
>>The speed of channel changing can be improved in other, better ways.  And
>>by 'better', I mean, 'applicable to every user, not just some'.
>I agree that keeping PVR capabilities whilst achieving speeds equivalent to 
>those which are already accepted in current TVs is the best goal. Is that 
>achievable though?!? Maybe I grab the wrong end of the end, but people seem 
>to suggest that the buffering/ringcache is responsible for most of the delay 
>and  now that eliminating it can't be done? 

You are replying to *MY* post where I stated that I had already patched 
an earlier version of myth to change channels on DVB in usually under 
500ms and sometimes much less.  This was done by fiddling with timeouts, 
buffer sizes and removing redundant pause statements

I really feel that this moaning about changing the implementation is 
heading in the wrong direction and just alienating the few people who 
can help fix it rather than helping

If someone has instrumented parts of tv_play and has a recent patch to 
show your code then please post it.  I think this helps other less 
technical people play with some instrumentation and track down their own 
timings.  ie it's fairly easy to cut and paste some code once someone 
has stuck the basic outline code in roughly the right place

The delays ARE solvable, they just need some investigation and time.  
It's NOT trivial to do this though because Myth is a multithreaded 
program and it's quite easy to accidently setup some race condition 
which breaks things.  But it IS possible, and *YOU* can help make it 
happen by reporting back on channel change timings based on some 
profiling of the code (not based on using your wrist watch and flipping 
channels mind)

Please help and get involved.  I would love to see this all get faster

Ed W

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