[mythtv-users] about transcoding and auto-transcoding

Phill Edwards philledwards at gmail.com
Fri Dec 2 00:29:28 EST 2005

> My impression was that setting a recording to auto-transcode will
> convert (after finished recording of course) from native mpeg2 (large
> filesize) down to divx or xvid or something with much smaller size.  Is
> that about right?

Not sure off the exact format other than you can transcode to MPEG4 or
RTJPEG. MPEG4 is smaller.

> Currently I have a 30 min daily tv show scheduled with auto-flag
> commercials and auto-transcode with default profile and autodetect
> transcoder.  Recorded 30 minute shows are still 1.1G in size.  The info
> in mythweb shows
> has commflag: yes has cutlist: no is editing: no auto-expire: yes has
> bookmark: yes
> Which seems pretty normal, except the size of 1.1G is pretty big, or is
> that indeed a smaller size.
> Also is transcoding related to the nuvexport script?

No - that's for putting it into a different format for us outside of
MythTV. Eg, when you want to archive recordings off to DVD etc.

> So my question is how can I tell if auto-transcoding is working, and if
> it is working, is 1.1G for 30 minutes normal?

Not sure what a reasonable size should be but I think around 700MB may
be more the mark. However, it depends on your transcode settings where
you specify bitrates for audio and video. The lower the bitrates (and
therefore quality) the smaller the file. So you need to go into
recording profiles and check how your transcode from MPEG2 to MPEG4 is
set up. Play with the setings until you get a quality/size trade off
you're happy with. There are usually 4 profiles where you can set
different settings - Default, LiveTV, Low & High Quality. I have mine
set up so Default does a reasonable quality transcode and High Quality
does no transcode and leaves it in MPEG2 off my DVB-T card. I use that
if I want to burn something I really want off to DVD.

The other thing is that you need to ensure your channel is set up to
auto-transcode. I can't remember where that actual setting is -
someone else will remember? It may even be in the profile settings.


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