[mythtv-users] Recording HDTV shows to DVD

[Cory Papenfuss]

 	The reason you haven't found it is that it's a lossy conversion. 
Most people who would want to archive an HDTV recording wouldn't want to 
downgrade it to SDTV (i.e. 720x480).  Since you asked, a few 
clarifications:

> Along the way I've discovered that HDTV broadcasts are
> in a format called MPEG2-TS (transport stream) which
> differs from other MPEG2 files.  Standard Myth tools
> such as nuvexport do not handle MPEG2-TS streams.

 	MPEG-TS is basically a wrapper for an MPEG-PS.  I believe it's 
got some additional packetization and other "Transport"-type doodads, but 
the actual video stream is the same.

>
> Another wrinkle is that HDTV broadcasts are often
> 1920x1080i or 1280x720p, whereas the highest
> resolution allowed on a standard DVD is 720x480, so
> some resizing of the video will be necessary.  Extra
> credit here for making an anamorphic DVD that retains
> the 16:9 format of the original broadcast.
 	Big wrinkle.  Basically, it's not high-def once it's 720x480.  You 
will need to reencode the video to 720x480, losing quality to bother 
resizing and another encoding genloss.  Also, it'll take oodles of cpu 
time... on a 2GHz machine, probably 5-10hours/hour for a good 2-pass 
encode.

>
> HDTV streams carry AC3 audio, but DVDs have either AC3
> or MPEG audio, so it may be necessary to create a
> two-channel audio track for use on DVD-players without
> builtin AC3 decoding.
 	No.  AC3 is more or less a wrapper as well.  Somone correct me 
if I'm a bit off on this, but MPEG audio in the DVD spec is MPEG1-LayerII. 
AC3 is MPEG2-LayerIII (a.k.a. MP3) if 2-channel.  If 5.1, it's different. 
HDTV audio stream should be able to go through unmodified.

>
> I have found several Linux programs which can handle
> portions of the above, but nobody has yet created a
> set of instructions for how to use them to archive a
> broadcast to DVD.  Did I miss the "Ultimate Guide to
> HDTV-DVD Recording" in my search?

 	Try avidemux for a fairly nice WYSIWYG cutting/transcoding 
program.  Feel free to take notes and write said missing guide.... :)

-Cory

*************************************************************************
* Cory Papenfuss							*
* Electrical Engineering candidate Ph.D. graduate student               *
* Virginia Polytechnic Institute and State University 			*
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