Trials and Tribulations with MythTV and FFmpeg

I’m running MythTV 0.24.1 at the moment with quite a few MythBuntu and other front ends. I’m running out of disk for recordings and decided to archive a few off to release some space which I’ve done with previous versions of MythTV fairly regularly. Unfortunately I discovered fairly quickly that asking nuvexport to transcode recordings to my preferred format (XviD) using ffmpeg was badly broken.

MythTV now includes its own copy of ffmpeg in the distribution to try to control some of the rapid changes of command line parameters the ffmpeg team seem to inflict on us with monotonous regularity. I discovered that it didn’t support libxvid out of the box for some reason (perhaps I didn’t have the necessary libraries installed at the time I built it). So, first step was to reconfigure it and rebuild. Only it won’t. The ffmpeg shipped with 0.24.1 looks like it just won’t link when libxvid is enabled.

So, I downloaded the latest git release and tried that. ffmpeg would now build, but doesn’t like that the libraries aren’t quite the same as the 0.24.1 versions, so I ended up rebuilding the entire package from the source, discovering in the process that libxvid wasn’t enabled again…

Eventually it dawned on my that I needed to add the command line switches:

--enable-libxvid --enable-gpl

on the mythTV configure command and this time all was well.

After reinstalling I kicked off nuvexport once more only to discover that it failed yet again, but this time because ffmpeg was being called with a parameter:


which the MythTV version of ffmpeg doesn’t support — it’s a later change to the code. I discovered that the older version of the parameter is:


So I edited /usr/local/share/nuvexport/export/ around line 335 to change:

push @filters, "setsar=1";


push @filters, "aspect=1";

This fixed the problem entirely and I got a full first encoding pass from nuvexport. Now it just falls over because ffmpeg doesn’t support the mp3 codec. That’s something to look at tomorrow.

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