Colour correction of a NTSC VHS captured via PAL Equipment

[alesco]

Hi everyone,

I am new here. I have searched for the answer but nothing helped. Thanks in advance.

My problem:
I have bought a media center device that can record from external sources. I have transfered some of my PAL VHSs (Im from Europe). I also have some NTSC cassettes (recorded from US TVs) and I wanted to transfer them as well. Everything went okay but the colours are off. (I know that transfering of NTSC tapes via PAL device causes troubles like black and white picture but I dont have anything else to transfer these tapes) SO, can anyone help me and tell how to post-process, restore the colours. I can use Vegas. I have attached a screencap of the picture with off-colours. Seems like there is too much green.



Question two (if it cant be corrected): Which PC graphic card supports and does vcr best NTSC/PAL VHS transfers?

[hech54]

I have bought a media center device that can record from external sources.

Which one?

[alesco]

Sencor SHR 9500T. It was not intented to be mainly for VHS transfers.

[hech54]

The only reason I asked is that it is difficult to find something that records NTSC tapes played through a PAL VCR. Thank you for the info.

[alesco]

No problems even though it did not offered any solution.. Also, when I connect the VCR straight into TV, it plays the NTSC VHS fine.

[hech54]

Also, when I connect the VCR straight into TV, it plays the NTSC VHS fine.

That's normal....recording it or capturing it is normally very difficult.....so difficult in fact that I'd leave your recordings alone....they look just fine to me.

[poisondeathray]

For example, you can use 3-way color corrector or curves in vegas if you feel image has too much green . Or in vdub you can use gradation curves and/or colormill

You have interlaced chroma artifacts , but that might be a result of the method of taking screenshot (looks like alternating horizontal red/green lines)

Hard to say definitively from 2 caps, but it looks like the top 20-30 pixels edge is colored differently than the rest of the frame. (There is a demarcation line where trees change color in the 2nd picture). You can use a mask to apply corrective filter

[alesco]

Okay, the line is present only on some of the videos so I would not generalise it.

Look, here are two screencaps (Green Day music video redundant, the optimal colours can be checked on youtube
1. The original captured video 2. My On the fly colour/sat correction in VLC


I do not know much about chroma/tint or adding/changing single colours/colours range but it should be possible to tune it better.

[poisondeathray]

Well "Better" is very subjective term . Unless you have a reference image of what it "should" look like , everything is a guess. For example, is that guitar supposed to be yellow? or peach ? If you had video of the incredible hulk, you might color correct him "pink flesh tones" but he's supposed to be "green". You get the idea...

In other words, there is no "correct" way to do it, you change it until you thing it looks right

The only "correct" ways - and this is still arguable (because original content might be graded differently than a color correct neutral image) - is to set the black and white point correctly and have full tonal range with broadcast legal colors . Look at the scopes in vegas - the waveform monitor, the vectorscope , histogram

[alesco]

thank you. I have capped the music video because you can compare the colours on youtube: http://www.youtube.com/watch?v=6ydpSVvXE9k&ob=av2e so you can see that it is really wrong on the screencap 1.

I will try the scopes.

[poisondeathray]

I see, If you assume that youtube video is "correct" - and it should be because it's "offical music video" , then you have a guide as to how to apply filters

Right off the bat you can see it's much more saturated , levels are different, and colors are shifted compared to the "VLC corrected" image . For example, and the "grey" walls are actually more teal or turquoise

There are many basic color correction tutorials on youtube for vegas . If you are still lost, you can post your specific questions and someone will help you

[lordsmurf]

One of the color channels is missing from the tape version.
The others are screwed up.

This cannot be repaired. Ever.

[themaster1]

@ alesco
if you have a retail tape with smpte color bars (can find them in music videos tapes generally) it should be easy to fix the colors, i have posted a solution for that some time ago

[jmac698]

LordSmurf is right, the 'v' color channel is missing, which should be fixed in capture somehow. Anyways, there's still a way to fix it to reasonable colors, which will give flesh tones, however some range of colors will be missing.

cu=utoy
cv=cu.Invert
ytouv(cu,cv,last)

The matching frames from the youtube version are 4645,4646.
There are better ways to fix this, what you would do is a type of hinted colorization, where luma and U channel give a hint to the true color. I wouldn't want to work on that now, there's hopefully a better fix in capture.
There's problems with the youtube version as well.

The hinting I'm talking about would work for color symmetrical about the uv axis.. let me think about this.. anyhow it would be a slightly better version of the simple script I made. It would actually work well for this video which has a limited palette.

[alesco]

Thanks for your ideas jmac698.

which channel is 'v'? Also, can it be actually added via chroma? Could you please somehow explain the process because I am not such skilled as you as I see from the post.

Eventually, I can upload a sample of the video, so you could do some tests.

Thanks again.

LordSmurf is right, the 'v' color channel is missing, which should be fixed in capture somehow. Anyways, there's still a way to fix it to reasonable colors, which will give flesh tones, however some range of colors will be missing.

cu=utoy
cv=cu.Invert
ytouv(cu,cv,last)

The matching frames from the youtube version are 4645,4646.
There are better ways to fix this, what you would do is a type of hinted colorization, where luma and U channel give a hint to the true color. I wouldn't want to work on that now, there's hopefully a better fix in capture.
There's problems with the youtube version as well.

The hinting I'm talking about would work for color symmetrical about the uv axis.. let me think about this.. anyhow it would be a slightly better version of the simple script I made. It would actually work well for this video which has a limited palette.

[jagabo]

which channel is 'v'?

http://en.wikipedia.org/wiki/YUV

Also, can it be actually added via chroma? Could you please somehow explain the process because I am not such skilled as you as I see from the post.

His inversion of the U channel to create a V channel is a nasty hack that just happens to create something like skin tones. The resulting video will have no greens or magentas, only oranges and blues. It's not a solution. You need to fix your capture method.

[alesco]

I thought it won't be easy to fix.. thanks.

Could anyone recommend the best way to capture NTSC VHSs in this case? I have got a Panasonic VCR (Can play NTSC without problems connected with my TV, it has only SCART output). The best way for me would be to connect the VCR to PC and capture raw video and sound so I could recompress it to best possible DVD format (MPEG-2 at 9800Mbps, PCM audio).

Any suggestions? Is there also a graphics card that can do that besides any TV Card?

[jagabo]

I have got a Panasonic VCR (Can play NTSC without problems connected with my TV, it has only SCART output). The best way for me would be to connect the VCR to PC and capture raw video and sound so I could recompress it to best possible DVD format (MPEG-2 at 9800Mbps, PCM audio).

You need a capture card that can capture PAL60 in that case.

[hech54]

....or an NTSC(only) VCR and a device to capture NTSC.

[jmac698]

Hi,
Think of a rainbow, but twisted in a full circle. Red is at the top. That's how colors are stored in video (they get converted to RGB later). Now think of the color as you go up and down in this circle, it goes between red and blue-green. That's the part that's missing. So red and blue are missing. How I fixed it was, I assume if there's some yellow/magenta (the other axis), I add in some red. This works for flesh tones.

I think my idea for a colorization of this will work very well for this particular video, except the red dress. I imagine the places it would screw up, it would be blotches of totally the wrong color in saturated areas. I could make it color locally the same tint based on the dominant hint for that patch. But it will never be perfect.

Jagabo said it better, and actually this kind of coloring is similar to 2 strip film, or early color film, which only had certain colors.

ps I just realized that what I did is the same as changing the tint. I'm rotating the colors 45 degrees.

[alesco]

Hi,
Think of a rainbow, but twisted in a full circle. Red is at the top. That's how colors are stored in video (they get converted to RGB later). Now think of the color as you go up and down in this circle, it goes between red and blue-green. That's the part that's missing. So red and blue are missing. How I fixed it was, I assume if there's some yellow/magenta (the other axis), I add in some red. This works for flesh tones.

I think my idea for a colorization of this will work very well for this particular video, except the red dress. I imagine the places it would screw up, it would be blotches of totally the wrong color in saturated areas. I could make it color locally the same tint based on the dominant hint for that patch. But it will never be perfect.

Jagabo said it better, and actually this kind of coloring is similar to 2 strip film, or early color film, which only had certain colors.

ps I just realized that what I did is the same as changing the tint. I'm rotating the colors 45 degrees.

Thanks for the explanation.

Well I would need a capture card to pci slot / usb with SCART input and support for NTSC tapes. Not high-end price. Any advice?

[hech54]

Well I would need a capture card to pci slot / usb with SCART input and support for NTSC tapes. Not high-end price. Any advice?

As I stated before.....you also need an NTSC ONLY VCR. Your "PAL that also displays NTSC" is not going to work.

[jmac698]

Not true - I can capture all PAL variations fine with my equipment. It's old though, bt8x8 wintv.

[hech54]

Not true - I can capture all PAL variations fine with my equipment. It's old though, bt8x8 wintv.

With the Sencor SHR 9500T .....yes.
That is why I asked you what device you are using. It is damn near impossible to capture the "quasi" signal output by an NTSC tape in a European VCR.

[jmac698]

You can see someone do it here http://www.youtube.com/watch?v=dpJ_ps_Rj5k

And EasycapDC60+ will work, it has the ntsc 433 setting.

The standard you are getting seems to be PAL60, which is NTSC with PAL color. It seems it's actually working to an extent, but why would V be missing? Is it possible the phase alternation is cancelling it out? I had a hunch, that if you could record raw YUY2 you'd be able to recreate the proper color.

Can you force it to record in different standards, like PAL, using amcap or virtualdub, and see what happens? I can always see a signal in different standards, just that sometimes it's b/w. And actually, it should be possible to write a filter to decode color from PAL60 recorded in NTSC mode, which will be b/w but with the color carrier visible.

Finallly, try capping in Linux. It seems that all modern chips support PAL60 in hardware, but that it isn't enabled in the drivers. In Linux you might have better drivers. You could try Mythbuntu live cd.