[mythtv] ivtv buffer overflow

Niels den Otter otter at kjoe.net
Mon Dec 12 16:47:35 EST 2005

Isaac Richards wrote:
>>I have been experiencing problems with corrupt ivtv recordings and
>>the buffer overflow messages since around September.  I thought that
>>these were linked to an ivtv upgrade, but now that I look at the
>>commit date of the bufferSize changes (09/21/05) in
>>mpeg_recorder.cpp, it looks like this corresponds almost exactly with
>>the start of my corruption.  I have changed the bufferSize to 32768
>>as you suggested on ivtv-devel and I am currently recompiling to test
>>the results.  I notice that prior to this change, the bufferSize was
>>256,000.  What is the reason for such a drastic reduction, it wasn't
>>mentioned in the commit message.  Would setting it back to 256,000 be
>>better than 32768?  I'll play around with it a bit and let you know
>>the results.
> Smaller reads make ivtv more responsive on channel changes & startup.

I have tried a bufferSize of both 32768 and 256000, but the problem is
still there. Strange thing is that it only happens when a recording
starts while watching LiveTV.  The recording is in the list, but the
ivtv driver keeps spewing the 'Overflow' messages and the image in the
recording is black.

If I quit LiveTV just before the recording starts all goes well. Is
there anything different in the path LiveTV->recording and
LiveTV->none->recording that could cause this?

Nothing strange in mythbackend ouput also:
2005-12-12 22:40:02.728 TVRec(1): Changing from WatchingLiveTV to None
2005-12-12 22:40:03.071 Finished recording Nova/Den Haag vandaag: channel 3
2005-12-12 22:40:03.278 TVRec(1): Changing from None to RecordingOnly
2005-12-12 22:40:04.170 Started recording: Piets weerbericht: channel 19
on cardid 1, sourceid 1
2005-12-12 22:40:04.302 scheduler: Last message repeated 1 times
2005-12-12 22:40:04.332 scheduler: Started recording
2005-12-12 22:40:05.505 Reschedule requested for id 0.
2005-12-12 22:40:06.225 Scheduled 84 items in 0.7 = 0.00 match + 0.72 place
2005-12-12 22:40:06.237 scheduler: Scheduled items
2005-12-12 22:41:51.242 mythbackend: Running housekeeping thread

Apart that it always seem to say 'Last message repeated 1 times'.

-- Niels

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