[mythtv] nuvexport incorrectly setting aspect ratio for dvb-t recordings

James Fidell james at fidell.co.uk
Sat Aug 4 10:05:35 UTC 2007

Chris Petersen wrote:
> James Fidell wrote:
>> I don't know if this is a valid fix, or applies only to dvb or dvb-t
>> recordings though.
> Valid fix.  Never even occurred to me that the frame restriction was
> getting in the way of some of that detection.  Changes committed both to
> nuvexport 0.4 and to the perl bindings in MythTV svn trunk (for
> nuvexport 0.5).

Good news :)

I'm finding a few related nuvexport problems that I'm not really sure
how to resolve.  Any hints or ideas about how to progress would be

First there's the one I think I've already raised about mplayer
reporting no audio for recordings that start before a DVB-T channel
begins transmission.  This causes ffmpeg to fail because the audio
sample rate values etc. aren't set.  This happens even though I have
cutpoints set to chop out the period where there was no transmission.
Even if I force the audio values to the correct values for the
programme I want exported, mythtranscode still dies, but that's
something else I need to look at in more detail.

Second, aspect ratio values can get set incorrectly where the aspect
ratio changes in the course of the recording.  For example, I have
a recording that starts at 4:3, then switches to 16:9 when the
programme I actually recorded starts.  Then I have my first cutpoint at
the place I wish to commence the export.  I guess there's a further
complication to this in that some programmes might be transmitted
at one aspect ratio with commercial breaks in another.

I can't find any way to persuade mplayer to report the audio/video
data at the first cutpoint rather than from the start of the file,
which seems like it would solve both those problems.  Otherwise
perhaps command-line options to force the aspect ratio, audio
sample rate and number of channels might be a helpful workaround.

Any ideas on these?  I'm quite happy to do a bit of coding in C or Perl
to test out possible solutions, but I'm sadly lacking in understanding
of video transmission/storage itself.


More information about the mythtv-dev mailing list