> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of
> Steven M. Schultz
>
> Thanks for making the data available - I pulled the
> images in and
> did a bit of experimenting tonight. The results were
> even better
> than I expected!
:)
> Now on to the evening's testing. What I was curious
> about was if
> doing the scaling and color space conversion with
> 'y4mscaler' would
> make a difference (hopefully for the better ;)).
>
> So, I took the 07_orig.jpg file and converted it to
> 24bit RGB PPM
> and used 07_orig.ppm as the source. 'ppmtoy4m' was
> used to convert
> to 4:4:4 Y4M format (lossless - just going from RGB to
> YUV, still in
> 24bit mode).
>
> Then the key step: I used y4mscaler with an 8 tap
> Sinc/Lanczos scaling
> kernel _and_ converted to 420_mpeg2 *and* took into
> account the fact
> that PAL pixels are really 59:54 and not 1:1 (if you
> just scale from
> 1360x1020 to 720x576 you're changing the aspect ratio
> when displayed
> on a TV!).
>
> The last step was to run the data thru the yuvcorrect
> program to get
> broadcast safe values. The result of this could have
> been piped
> directly into mpeg2enc but I created a .y4m file that I
> could use with
> other programs.
>
> Encoding was done with "-q 1" and a bitrate of 9800.
> The resulting
> .m2v file was ~84K bytes ("84095 22 Jul 19:52 xxx.m2v")
>
> To view the results it's necessary to decode the .m2v
> file back to PPM.
> That is done using 'mpeg2dec' and a couple more of the
> mjpegtools
> utilities (pgmtoy4m and y4mtoppm). y4mscaler was used
> to convert
> upsample to 4:4:4 (24bit mode). pgmtoy4m is I believe
> only in the
> CVS version of mjpegtools at the moment but I might be
> mistaken about
> that (it's been eons since I've used anything except
> the CVS version ;))
>
> The script I used was this:
>
> ----------
> #!/bin/sh
>
> cat 07_orig.ppm | \
> ppmtoy4m -n 1 -F 25:1 -I p -S 444 | \
> y4mscaler -I sar=1:1 -O sar=PAL -O size=720x576 -O
> chromass=420_mpeg2 -S option=sinc:8 | \
> yuvcorrect -Y CONFORM > 07_orig.y4m
>
> mpeg2enc -f 8 -b 9800 -q 1 -o xxx.m2v < 07_orig.y4m
>
> mpeg2dec -o pgmpipe xxx.m2v | \
> pgmtoy4m -a 59:54 -r 25:1 | \
> y4mscaler -O chromass=444 | \
> y4mtoppm -L > 0.ppm
> ----------
>
> I have attached a script of the session so that you can see the
> output of the tools. The output from y4mscaler will be
> of interest I
> believe.
>
> Maybe I'm overdue for getting new glasses but to me the
> .m2v file
> produced above looks sharper and clearer than either
> 07_commercial.png
> or 07_mpeg2enc.png. The differences between the file
> produced above
> and the .png files are subtle to my eyes even at a 2x
> zoom in the
> GIMP (using Apple's 23" Cinema-HD LCD screen). I'm
> sure that With a
> higher bitrate the differences would be even smaller but the
> sharpness in the file created by the above script is noticeably
> better than the 07_commercial.png and 07_mpeg2enc.png -
> those almost
> look "blurred" in comparison ;)
>
> Perhaps someone with better eyes (or newer glasses :))
> can run some
> tests and chime in on this - another opinion would be welcome.
For the moment, I'm not yet able to compile the CVS version of mjpegtools (see other
thread).
Could you sent the resulting .M2V you got to me, so that I can already take a look at
it?
BTW: Nice monitor you have there ;)
Regards,
Marc
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