[mythtv-users] RE: about transcoding and auto-transcoding

Daniel Howell howelld at brumster.com
Fri Dec 2 08:51:58 EST 2005

Interesting, because I'm having thoughts over similar problems/ideas.

Here is my understanding - someone correct me if I'm wrong.

I'm using DVB-T here in the UK, so it's in a native MPEG2 format when it
comes down.

I believe the "Hardware Encoder" profile in Myth is pointless in this
regard, because the Hauppauge cards I'm using just dump the video straight
out in it's native format, and myth is just dumping this to disk with no
decoding required; hence pretty much no processor usage while recording.
This I'm all fine with.

The "Transcode" profile is what gets automagically run against recordings
after they've completed, and I have two options - to MPEG4 (which is
basically DivX, right?) or RTJpeg (which I'm basically steering clear of,
full stop).

What I want to achieve is this :-

Default recording profile - no transcoding whatsoever; the idea here is that
the recordings are just to briefly watch back and probably not keep, and
hence will be deleted soon enough anyway.

High Quality - I'd like any programmes recorded against this to go through
ffmpeg purely to make the MPEG2 stream fully DVD compliant; I find the DVB-T
files in raw format (ie. Rename .nuv to .mpg) don’t play in your average
browser. So Default means basically a run through transcode MPEG2->MPEG2 to
the appropriate DVD spec.

Low Quality - this profile I want to take down to DivX (MPEG4) and reduce
down slightly in resolution and size. This will be for archiving purposes,
but to a PC and ISO CD/DVD formats as .avi files, rather than any need to
burn them to DVD as playable DVD movies.

PSP - I'd like to create a new profile too which takes the video through
ffmpeg again, making it a compliant PSP stream (which I think is MPEG2 with
some audio restrictions?). Obviously the main thing here is a major
resolution reduction. I use pspvideo9 so I can rob the ffmpeg parameters out
of this.

So my question is - is that all doable?

Low Quality looks easily configurable via the standard Myth settings page.
High and PSP I'm not so sure of. Previously I've used nuvexport to do things
manually, but I'd like the whole process to be a bit more automated in the
background, maybe overnight. Am I maybe better off leaving this out of myth
itself, and scripting nuvexport in some way?

Any thoughts most welcome ;)

Dan Howell
Birmingham, UK

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