Video DVD quality loss with mencoder/dvdauthor/growisofs

[Polytropon]

Currently I'm searching for a way to create MPEG files suitable
for creating movie DVDs. My source files are SD videos with the
following properties:

	container: AVI
	video: DivX DX50, 640x360 px, 24 bpp, 25 fps
	audio: MP3, 44.1 kHz, 2 ch, 128 kbps

I'd like to "inflate" the video for DVD resolution. When I use
mencoder to do so, the graphics gets "blocky". There are no
visible compression artifacts in the source video, but the
result is really terrible. I know I cannot "increase quality"
when doing 640x360 -> 704x576, but it should not get worse.

My solution is a script "avi2dvd" which uses mencoder, dvdauthor
and growisofs to prepare the required data structures and then
burn them onto DVD+R media. The DVD players I tested them with
play the result format, but show the "blocky" video just like
a software player (both by checking the .mpg and .vob files),
so the postprocessing steps do not introduce that significant
quality loss.

At its heart, the script contains this step:

	mencoder -oac lavc -ovc lavc -of mpeg -ofps 25 \
		-mpegopts format=dvd -vf scale=704:576,harddup \
		-af lavcresample=44100 -srate 44100 \
		-lavcopts vcodec=mpeg2video:keyint=15:vrc_buf_size=327:vrc_minrate=1152:vbitrate=1152:vrc_maxrate=1152:acodec=mp2:abitrate=224 \
		-o ${MPEGFILE} ${AVIFILE}

This reflects the parameters I got from the mplayer documentation
on the web where this approach is listed for creating DVD files.
But as I said: The quality is terrible.

(Sidenote: I will additionally need to experiment with -vf crop
in order to deal with mis-aligned video sources.)

Can anyone provide a _verified_ method that _does not lower_ the
resulting video quality?



-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...