Hello,
I understand that MJPEG is (more or perhaps less) a concatenation of JPEG
files; hence I'd thought that extracting the JPEG files, rotating them
lossless and then bringing them back together should be a lossless
operation.
You've already guessed, this is not the result I come to. The result is
not bad, but the film becomes with each rotation always more noisy and
muddy.
My current sequence looks like this:
1# /usr/bin/transcode -y jpg -o '.tmpmjpg/' -i '0755_MVI.AVI'
--print_status 10,0
2# /usr/bin/transcode -i 0755_MVI.AVI -o .tmpmjpg/film.wav -y null,wav
3# (for each jpg file) jpegtran -rotate 90 -copy all nnnnn.jpg
4# /usr/bin/mencoder mf://.tmpmjpg/\*.jpg -mf
w=480:h=640:type=jpeg:fps=30.000 -o .tmpmjpg/0755_MVI.AVI -ovc lavc
-lavcopts vcodec=mjpeg:vhq
5# /usr/bin/lavaddwav .tmpmjpg/0755_MVI.AVI .tmpmjpg/film.wav
0755_MVI.AVI.avi
So, my questions at this point:
1. is the theory wrong?
2. or are the tools wrong?
3. or the way I use the tools?
4. what could I do better/perfect?
Thanks, Eric
PS: I thought about replacing step 4 with mencode through something like:
# ls -1 $tmpdir/*.jpg > $tmpdir/list
# transcode --use_rgb -i $tmpdir/list -x imlist,null -g ${w}x${h} \
# -y ffmpeg,null -f $output{'ID_VIDEO_FPS'} -H 0 -F mjpeg -z -k \
# -o catfile($tmpdir, $file)
but it doesn't really make things easier (perhaps better but first tests
didn't give me this impression).
--
Eric de France, d'Allemagne et de Navarre
