[mythtv-users] Converting HDTV to SDTV

Mike Holden mythtv at mikeholden.org
Thu Jan 29 16:26:22 UTC 2009


Adam Siegel wrote:
> I just replaced my PVR350 with a pair of AVerTVHD MCE A180s in preparation
> for the HDTV deadline.  Yes, I use an antenna - no cable here.  Having two
> cards is great as I can record more than one program at a time.  I had
> very
> few problems with their install, thanks to this forum.  They are working
> perfectly.
>
> My front-end units on a couple of the televisions in the house are
> Hauppauge
> MediaMVPs.  I've used the mvpmc distro for a couple of years now without
> any
> issues.  However, these units can't process the 1920x1080 mpeg2 stream
> (not
> to mention network bandwidth issues).  So I need to transcode the
> recordings.
>
> I can't seem to get a good read on what to use and the paramters for the
> various programs.  I have tried both mencoder and ffmpeg.
>
> The first thing I do is check to see what resolution the recording is by
> doing
>
> $w = `mplayer -nosound -vo null -ss 03:00:00 -really-quiet -identify $F1
> 2>/dev/null | grep ID_VIDEO_WIDTH`;
>
> in a perl script.  If the width is less than 720, the the MediaMVPs seem
> to
> work fine and no transcoding is necessary.  However if it's greater than
> 720
> I transcode with ffmpeg
>
> ffmpeg -i $F1 -croptop 12 -target ntsc-dvd $F2
>
> I needed to add the croptop because there is some noise that I get in the
> recording (don't know why).
>
> Anyway, with ffmpeg I have noticed some voice sync problems with the
> MediaMVP.  The picture looks fine.  Playback on a PC using either the ASX
> stream from MythWeb or using MythTVPlayer on widows is fine.
>
> Appreciate any advise available for a better transcoding method!!!

I've often had sync problems when transcoding to mpeg2 for my mvpmc.

Maybe try using vlc on the backend (or some other Linux box on the
network)? There's a wiki entry on the mvpmc website showing how to set
this up.

You may not need to transcode in advance, depending on the box power that
you use, as it does it on the fly and seamlessly streams it.
-- 
Mike Holden

http://www.by-ang.com - the place to shop for all manner of hand crafted
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