Grayscale Filter for B&W movies?

[Yo]

With a b&w still photograph, if one scans it grayscale, and saves it grayscale, it has a much smaller file size than if one scans and saves it as a color photograph. (Although the colors aren't there, only grey scales, if saved as a color photo it takes up a lot more space, I guess looking for those 24 million colors, rather than 256 gray scales.)

What about when encoding a B&W film? Would saving it grayscale save a lot of file size?

I see that in Vdubmod there is a filter one can apply to save grayscale. It says it converts a color movie to grayscale. But what about if it is used on a B&W movie, of course already grayscale? Of course then no filter is needed to see the film in grayscale, but would that significantly save on file size?

[Tommy B.]

It depends on the picture of want to save. You might think the picture is B/W but it could contain a little bit of yellow which you don't recognize but the codec does.

When you use the greyscale filter in Vdub you force the picture to 256 colors and a video codec won't save more than these, would be stupid if it would do so.

You can force XviD to encode to greyscale and I recon there was a FAQ which said that encoding to greyscale in XviD will create a smaller filesize than encoding without this option checked.

[Yo]

Originally posted by Tommy B.
It depends on the picture of want to save. You might think the picture is B/W but it could contain a little bit of yellow which you don't recognize but the codec does.

When you use the greyscale filter in Vdub you force the picture to 256 colors and a video codec won't save more than these, would be stupid if it would do so.

You can force XviD to encode to greyscale and I recon there was a FAQ which said that encoding to greyscale in XviD will create a smaller filesize than encoding without this option checked.

Do you mean that there is an option within XVID configuration itself to make the movie save as grayscale? Or to use the greyscale filter in VDub?

[niamh]

Do you mean that there is an option within XVID configuration itself to make the movie save as grayscale?
Yep. It's called Greyscale. :p

It's in the zones options tab.

[Yo]

Originally posted by niamh
Yep. It's called Greyscale. :p

It's in the zones options tab.

Well then, if compressing a b&w video with XVid in VDub, which place would be better to set a BW dub--with the Vdub greyscale filter, or with the option in Xvid? Or both??

[Tommy B.]

You might choose both if you want to. But logicaly seen enabling
greyscale in XviD would be the smartest solution.

[stickboy]

Originally posted by Yo
[B]With a b&w still photograph, if one scans it grayscale, and saves it grayscale, it has a much smaller file size than if one scans and saves it as a color photograph. (Although the colors aren't there, only grey scales, if saved as a color photo it takes up a lot more space, I guess looking for those 24 million colors, rather than 256 gray scales.)A color photo stores identical red, green, and blue color channels. Two of the channels clearly are redundant, so 66% of the space (assuming no compression) is wasted.
What about when encoding a B&W film? Would saving it grayscale save a lot of file size?It depends entirely if the output codec supports it. If it doesn't, then it'll end up doing the same thing: wasting color channels with identical information.
I see that in Vdubmod there is a filter one can apply to save grayscale. It says it converts a color movie to grayscale.Like all VirtualDub filters, its grayscale filter outputs RGB video, so it's wasting channel data. Adding it to your filter chain will only slow things down unnecessarily.

[niamh]

Originally posted by Stickboy:
Like all VirtualDub filters, its grayscale filter outputs RGB video, so it's wasting channel data.

That's very interesting, I never thought of this...what's Xvid's take on this greyscale encoding? should I use search? :D
What would be the best way to capture B&W stuff?