[mythtv-users] re: choppy HD playback

[Brandon Beattie]

The files stored to disk from the pcHDTV are mpeg2 streams (Not NUV
formated streams).  Transcoding for me consists of setting up the
transcoding config in Myth and letting it run.  How well it works has
been very inconsistant.  It worked 80% of the time several months ago,
but recently it's only doing about 30%.  I transcoding to 3 settings,
low quality (480x320) default (720x480) and high (1024x576).  (Those are
my 3 transcoding profiles).  When transcoding, all de-interlacing is
done and is very nice and good on performance after (30% CPU for me to
watch a show).

--Brandon

On Wed, Apr 21, 2004 at 08:53:25AM -0700, John Sturgeon wrote:
> HI Brandon,
> 
> I'm wondering what you use to transcode your HD nuv files.  Do you use 
> nuvexport, and if so what output format and settings do you use.  I too 
> have a 2600+ and find 1080i to be 'less than optimal'.
> 
> Thanks,
> 
> --
> John Sturgeon <><
> 
> Brandon Beattie wrote:
> 
> >Scott,
> >
> >I run an amd 2600+, I have problems running 1080i also.  It will run
> >fine if you turn of de-interlacing in the tv playback setup.  However,
> >the current algorithm for deinterlacing does not work well for high
> >resolution files (Such as HD).  At one point someone mentioned they were
> >going to write a couple new deinterlacing algorithms to help, but that
> >was a couple months ago.  In the future, your 2500+ /may/ be okay.  Most
> >of the problem with HD streams is not really myth, but the X server.  X
> >is very poor when trying to display HD.  (Not to mention it does not do
> >a good job at syncing frames and keeping video smooth).  When X is
> >re-written (as there is a project going on for this now) it will work
> >much better and will have true v-blank support.  You should be able to
> >watch 1080i on about a 1.7Ghz (This is what is required for windows that
> >properly handles v-blank and has a good de-interlacing for HD I've been 
> >told).  I personally recommend a P4 3.0Ghz with HT.  It almost doubles
> >your speed in regards to decoding HDTV and letting X suck up more
> >CPU cycles than it should really need.  The same stream on my 2600+ that
> >maxes out my CPU and is basically unwatchable, takes about 70% CPU usage
> >on a P4 3.2Ghz with HT.  Other possible issues are the way mythtv scales
> >video that is not native display size.  Right now, I (try to) transcode
> >all programs to 1024x576 (my native display size).  Transcoding is a bit
> >broken right now, but this takes care of things for me, but I don't
> >watch livetv, and this also saves disk space.  I also recommend a higher
> >CPU because if you want to transcode, the border line is not good.  Even
> >when watching transcoded shows, if the transcoder kicks in I can notice
> >it on my 2600+, the P4's with HT don't appear to be noticible.  I'm
> >waiting a bit to see if I can't find a dual P4 MB for cheap in a half
> >year and I'll pick up one of those for my mythbox.  Transcoder can use 1
> >processor, and my dvd, or livetv (If I do use it) can use the other.
> >
> >That's my $.02
> >
> >--Brandon
> >
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