Howdy -
What a difference a VCR makes!
The JVC S-VHS deck I'd been using for several years "wore out" (a LOT
of tapes, most of which were in bad shape, went thru it) - blurry
picture and the brightness was gone (Y' above 164 was rolled way off).
So, until I could get a new one ordered I had to borrow my brother's
cheap Panasonic (it was his tape I was converting and he couldn't wait
until I could get a better VCR ). The Panasonic didn't have an
S-Video output so I enabled the 3D Y/C separation in the Canopus ADVC300
Anyhow, to make a long story at least a little bit shorter... ;)
At the beginning of the movie there was about a minute and a half
of black with the orchestral prelude. I captured that segment with the
Panasonic and the new JVC HR-S9911U.
Wow! I won't include the entire 'y4mhist' output - but the Panasonic's
black level is WAY UP, the center's around 26. No wonder it looked
washed-out and the grey blocks/splotches were easily seen. Dragging the
blacklevel way down about 10 units in FinalCut worked wonders for
the appearance of the video! As a pleasant side effect, lowering
the blacklevel and desaturating the lows got rid of a lot of noise which
resulted in y4mdenoise had an easier job later on and ran faster ;)
By way of contrast the JVC is giving 'superblack' - values below 16.
Also apparent is that the cheaper decks introduce a lot of noise.
Encoding (with no filters at all) the two captures to "DVD rate" .m2v
files produced a file for the Panasonic that was 2x the size of the
one from the JVC.
From the Panasonic:
Y 0 0
Y 1 0
Y 2 0
Y 3 0
Y 4 0
Y 5 0
Y 6 0
Y 7 0
Y 8 0
Y 9 0
Y 10 0
Y 11 0
Y 12 0
Y 13 3
Y 14 23
Y 15 1963
Y 16 134790
Y 17 1986945
Y 18 2577014
Y 19 1073756
Y 20 567146
Y 21 352359
Y 22 645264
Y 23 1027007
Y 24 10730720
Y 25 132937699
Y 26 590599528
Y 27 205187805
Y 28 89761622
Y 29 2605866
Y 30 165259
Y 31 43564
Y 32 17981
Y 33 13705
Y 34 11387
Center's up around 26 to 27 - that's quite bright for "black". And
the counts up thru 40 are quite high compared to the values for the
other deck.
From the JVC 9911:
Y 0 830363
Y 1 15366982
Y 2 11002871
Y 3 2911416
Y 4 1313861
Y 5 1249223
Y 6 1535257
Y 7 3121024
Y 8 42465254
Y 9 275993484
Y 10 346509902
Y 11 231089270
Y 12 69087050
Y 13 21825445
Y 14 8038107
Y 15 4525798
Y 16 2641215
Y 17 445571
Y 18 179641
Y 19 106988
Y 20 82776
Y 21 51984
Y 22 23475
Y 23 11121
Y 24 7672
Y 25 6157
Y 26 5237
Y 27 4651
Y 28 4197
Y 29 3998
Y 30 3718
Y 31 3455
Y 32 3109
Y 33 2686
Y 34 2652
Interesting - the center leans to the 'superblack' range. Those will
eventually get cored which will effectively move the center range
from 11 to 16
So, same tape but two different tape decks produce wildly different
results.
So if your captures are looking a bit too washedout/light (blacks look
grey) you might want to take a close look at the black levels of the
stream and adjust them down (yuvcorrect can do this I believe) somewhat.
Pick a representative (ideally completely dark) scene and get an idea
what the average black level is and then adjust down until you're
close to 16 or perhaps even a little on the 'superblack' side.
Once the lower level is set then you have room at the middle or high
end to increase the brightness/contrast some.
Of course it's easier to do when you can visually see in real time
what's happening :-)
If you're looking for a good VCR then JVC's one of the few companies
still making S-VHS decks with an S-Video output (most stores don't
carry S-VHS decks - I went online and ordered it). Couple nice features
of the JVC 9911 are the builtin TBC (TimeBaseCorrector) and DNR
(Digital Noise Reduction) which stabilize the picture and do a little
cleanup of the worst of the noise. The stabilization so far has
done a great job of producing the active/meaningful 704 pixels centered
in the 720 pixel DV frame - haven't had to use 'y4mshift' to shift
right/left yet.
Cheers,
Steven Schultz
-------------------------------------------------------
This SF.Net email is sponsored by Oracle Space Sweepstakes
Want to be the first software developer in space?
Enter now for the Oracle Space Sweepstakes!
http://ads.osdn.com/?ad_id=7393&alloc_id=16281&op=click
_______________________________________________
Mjpeg-users mailing list
Mjpeg-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/mjpeg-users
