santa8claus wrote:
> Looking in mythbackend.log I noticed the message:
> 
> MPEGREC(/dev/video1) Error: Error getting codec params using old IVTV ioctl 
> eno: Bad address (14)

This is MythTV testing to figure out how it should call the ivtv driver
ioctls to set bitrate and other encoder parameters: using old ivtv
ioctls or new V4L2 ioctls.  It can safely be ignored.


> MPEGRec(/dev/video1) Error: select timeout - ivtv driver has stopped 
> responding

The is MythTV (rightly) griping about how the cx18 driver failed to say
any data was available for read()-ing for 5 seconds on the second file
descriptor of the cx18 device node MythTV has open.  (The first one
MythTV uses for control functions of the cx18 driver.)

MythTV will then proceed to make matters worse for itself by closing the
2nd fd and trying to reopen it again - thus staying in a cycle of
failure.  This strategy may have worked around some early ivtv driver
problems, but it doesn't help with the beta cx18 driver.

See the main while() loop in  MpegRecorder::StartRecording() in the file
mythtv-fixes/libs/libmythtv/mpegrecorder.cpp.  The select() is timing
out because the cx18 driver isn't saying data is available.


> Anyone know what this means or can figure out the reason for the failure?

The underlying reason is somewhere in the cx18's driver logic, or how it
sets up the digitizer and encoder. I only have a few hours on the
weekends to play with this stuff, so I don't think I'll be the one to
find the root cause before analog NTSC broadcasts turn off in the US. :)

I can say with some confidence, that its probably not the NTSC tuner
settings.  The symptoms appear to be same whether using the Tuner or the
Composite 1 input (using the little RCA/S-Video adapter provided with
the unit).

The symptoms do appear to be affected by signal processing by the
digitizer.  Having the digitizer do adaptive chroma subcarrier locking
rates makes the symptoms less severe, if you accept the time
"cat /dev/video1" spends in blocking read()'s as a valid metric.  I
assume this digitizer setting change makes life easier for the encoder
and makes it more responsive.


-Andy


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