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View Full Version : VCR output PAL tapes as PAL-M-50 hz!


vmesquita
13th May 2003, 19:11
Hi everybody,

When I was buying a VCR this year, a choose the only model that could play PAL-B/G/N tapes (a panasonic model). But when I finally got a PAL-N tape to test, I found out that it plays the tape at 50 hz, but converts the color information to PAL-M (and later I checked the manual, and it says clearly that PAL tapes will only work with TVs that support PAL-M at 50 hz). (PAL-M is NTSC with different color codification)

I am using BTWinCap drivers and tried every broadcast mode with no success... The closest think I got is choosing PAL-NC, this way I could get a color image (but the colors were misplaced, green becomes blue and vice-versa and so on...). I mailed Eduardo (the BTWinCap author) asking if there's a solution. But I was thinking that maybe some avisynth filter could correct the chroma information.
Then I did an experiment: got a PAL tape, played on the VCR. It had that inicial color bars on the beggining. I set to PAL-NC and captured. Then I set to PAL-M (colors right, but image desync), and captured. And I run throught the following script:

a=AVISource("PAL-NC.avi").bilinearresize(320,240)
b=AVISource("PAL-M.AVI").bilinearresize(320,240)
ret=mergechroma(a,b,1)
return(ret)

There might be spelling error since I don't have the script here, but it was more or less like this. Well I got a image with desynched chroma, but right colors on top! Now I ask you:

Is it possible to calculate the color differences (maybe in RGB or other colorspace) and apply a script that would correct the colors in the movie? Any ideas? Any help would be very appeciated.

[]'s
Vmesquita

sh0dan
15th May 2003, 17:37
Maybe someone here can help you.

vmesquita
15th May 2003, 18:10
Thanks Sh0dan.

Unfortunatelly, I have been talking to BTWinCap author and we came to the conclusion that the colors are being captured wrong (not inverse colors, chorma or something like that)...
I mailed him asking if it's possible to implement some kind of PAL-M-50, like NTSC-50 or PAL-60, since BT878 allows to set the number of lines.

[]'s
Vmesquita

vmesquita
19th May 2003, 01:53
Update:

I modified BTWincap Drivers to support PAL-M-50. It's a one line change! :-)

[]'s
Vmesquita