[mythtv-users] Transcoding

Paulin paulin at spextreme.com
Mon Dec 1 01:20:41 UTC 2008


On Sun, Nov 30, 2008 at 7:47 PM, Brian Wood <beww at beww.org> wrote:

> On Sunday 30 November 2008 17:20:15 Paulin wrote:
> > On Sun, Nov 30, 2008 at 6:11 PM, David Greaves <myth at dgreaves.com>
> wrote:
> > > Paulin wrote:
> > > > I've been recently playing around with transcoders and got something
> > > > working for reformatting HD so my frontend can handle it.
> > > >
> > > > Now I'm curious if there is a way to have the transcoder run as the
> > > > stream is read in.
> > > >
> > > > For example
> > > >     Video card -> mpeg2 stream -> transcode -> write to file
> > >
> > > Unless you're transcoding more quickly than real-time then the backlog
> of
> > > data
> > > in the stream will need to go somewhere; typically to disk...
> > >
> > > David
> >
> > Let me try asking this again because I may not have explain it good.
> >
> > Right now it looks like when something records it finishes recording (60
> > minutes later) then it runs the commercial flagging and then the
> > transcoder. The transcoder takes as long as the program did (60minutes).
> > So I'm wondering if it is possible to run the transcoder as it records
> > instead of after.  The comercial flagging I could hold on till the end
> for.
> >
> > Basically the reason I'm asking is currently my front end can not handle
> HD
> > recordings.  So I would like ti to be read by the card, transcoded, saved
> > to disk, then played on front end before the show end.
> >
> > Hopefully that make sense.
>
> Yep, you want to transcode on the fly as you capture, then record.
>
> Since you are going to watch in SD anyway,  most programs are broadcast in
> SD
> as well, could you just try and record that in the first place?
>
> If not, I think there is a setup parameter that sets how often to scan for
> jobs (like transcode jobs). I think the default is 1 hour. If you can find
> that and shorten it up a bit, you could get the transcode job to start a
> lot
> sooner.
>
> Transcoding puts a load on CPU and disk I/O. Depending on your hardware,
> you
> might nnot be able to handle watching, recording and transcoding at the
> same
> time. You could nice the transcode more, but of course this will slow it
> down.
>
> If the source material is h264 I suspect you are asking too much of all but
> the fastest systems, but if it's MPEG2 you can probably get away with it.
> I'd
> worry about the disk I/O more than the CPU, unless it's h264.
>
> --
> beww
> beww at beww.org
>

Thanks.  I did change the queue rate to be 5 seconds.  However I can't get
the transcoder to run automatically at all.  I've setup the recording to run
them, I have the transcoder configured so it will run before commerical
flagging but it just never runs.  I can only get it to run if I manually
start it.

Any thoughts as to why it isn't starting automatically.  The recording is
set to run the transcoder and everything.

Thanks
steve
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