[mythtv] HD3000 buffer overrun solution - patches for hdtvrecorder.cpp/.h against mythtv 0.16

[John Patrick Poet]

Here is my version of a ringbuffer thread for hdtvrecorder.  I had not 
actually planned on posting this quite yet, but since this is now a hot 
topic, here you go.

This is against the current CVS with Daniel's hdtvrecorder patch applied:

http://www.mrl.nyu.edu/~danielk/mythtv/hdtv-recorder-v35.tbz


I actually hope that Eric Anderson's version is more effective than 
mine.  I won't have a chance to test his for a couple of days, though.

Isaac's idea of creating a thread for the sole purpose of syncing the 
file system helped a lot, but I still cannot consistently record three 
shows while watching another for more than 90 minutes.  I can record a 
single show all night long without more than 4MB of ringbuffer being used.

Recording three shows simultaneously works great until a magic wall is 
hit.  Until that wall is hit, each of the three shows will use anywhere 
from 1MB to 10MB of the ringbuffer.  I have seen a recording use 10MB 
only to fall back down and use less than 1MB.  I have not done much 
testing with only two shows recording.

Once this magic wall is hit, ringbuffer usage suddenly doubles up to 
20MB for all three shows.  Within 10 minutes it will be up to 50MB.  
Within 5 minutes after that the ringbuffer usage is at 96MB (the max) 
and things have gone to hell.

Before creating a separate thread for syncing the file system, that 
magic wall occurred around 50 minutes into a show.  After creating that 
filesync thread, I don't hit that wall until 80 minutes in.

John

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