[mythtv] Random blockiness that probably isn't CPU or PCI bus bandwidth-related

Eric Anderson rico99 at sbcglobal.net
Wed Jan 19 00:37:42 EST 2005


> I have not tried your latest version.  When I tried to remove the 
> "double buffering" when reading from the ringbuffer, I needed to 
> greatly increase the ringbuffer to get it to work as well.  I also 
> never increased the internal buffer size in the HD-x000 driver -- 
> maybe that is why my results differed from yours.  If I have time this 
> weekend, I will try your latest version.  I assume it applies to the 
> latest CVS?

Actually, I'm not 100% up-to-date. But hdtvrecorder.cpp and 
hdtvrecorder.h haven't changed
since I last updated. So it should still apply. If you have a chance to 
try it out, that would be
cool.

BTW - With my version I don't get any buffer overruns at the end of a 
recording. (I have the
reader thread close() the device so we don't have the case where the 
main thread tells the
reader to stop reading, process remaining data, then close -- during 
which time the device
driver hits an overrun.) I *do* still sometimes get a buffer overrun 
when multiple recordings
start up. But it's normally a one-time thing.

I'm wondering if *any* buffer overrun poisons the device driver for 
later. (Just a theory...)
Because with the CVS version, I pretty much always get a buffer overrun 
at the end of
the recording. Like you said (below), maybe the 1.6 driver fixes some 
stuff.


> Have you tried the v1.6 driver?  It seems to work well for me -- 
> although it may be why I see an occasional overrun now, when I didn't 
> a couple of weeks ago (I was using the 1.5 driver).
>

I haven't. But I think I reviewed diffs of the code from 1.4 to 1.5 to 
1.6 and I didn't see anything related
to the CX8800 stuff. I am planning to try that out, though. Just 
haven't gotten to it yet.

> Maybe increasing the internal buffer size in the HD3000 driver is 
> causing a problem?  Probably not.  I have seen the corruption you are 
> talking about, but not in several weeks.  That is why I think it may 
> be fixed in the 1.6 driver.

Good data point. Let me get back to you on that.

Thanks.

-Eric



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