[mythtv] Should mythtranscode be preserving closed-captioning data?

[f-myth-users at media.mit.edu]

In MythTV 0.18.1:

Running mythtranscode -V all -c [chanid] -s [time] -p autodetect -d
doesn't seem to copy closed-captioning data from the input stream to
the output stream, or perhaps the xv driver that's running to send the
data to my PVR-350's output isn't passing it through or something.
I'm not actually sure how to tell if it's in the MPEG4 or not and
thus where it's getting lost.

Is this a bug, an oversight, a design decision, or is there something
else I need to do?  Swapping the original MPEG2 into my recordings
directory and playing it via Myth shows the CC just fine, but if I
rename that file and rename mythtranscode's MPEG4 in its place, I
get no CC data.  (And, of course, very low audio volume, as I reported
a couple of days ago and which I still don't have a solution for.)

Any clues?

Thanks.