Black and White Video?

[Yo]

If one is encoding a black and white movie (either ripped from DVD, recorded from VHS, or recorded from television), is there a way to specify it as grayscale during encoding, and save on file size that way.

For instance, with still pictures, if one scans a black and white photo as a color photo, it will take up as much space as a color photo. But if one converts it to grayscale in an image editing program, it will look the same, having been in grayscale to begin with, but will create a much smaller file size when saved (256 shades of gray, rather than millions of colors).

Is there any way to do that when encoding video, from a black and white film? To save as grayscale, in order to get a smaller file size?

[manono]

Yes, you can add one of a number of AviSynth filters to the .avs.
Tweak(Sat=0)
Greyscale()
are 2 of them. Don't count on shrinking the video size very much, though.

[chilled]

is there a way to do this in AutoGK or does the program do it "automatically"?

optional question:
"Don't count on shrinking the video size very much, though"

why that?

[unskinnyboy]

Originally posted by chilled
is there a way to do this in AutoGK or does the program do it "automatically"?

A not-so-straight forward way:

Under 'Hidden Options':
http://img204.exs.cx/img204/3827/greyscaleagk2ov.jpg

Chose framerate accordingly.

[chilled]

yeah thank you, I had thought of it before. but you loose the ability of compressing credits. And maybe that option does other things (like worst encoding or modifying Len0x's CLI commands or something, I really dont know Im just wondering uh? because obviously this hidden option isnt designed for that so maybe it has seccondary -unwanted- effects).
anyway thank you for intant response!

[unskinnyboy]

Originally posted by chilled
yeah thank you, I had thought of it before. but you loose the ability of compressing credits. And maybe that option does other things (like worst encoding or modifying Len0x's CLI commands or something, I really dont know Im just wondering uh? because obviously this hidden option isnt designed for that so maybe it has seccondary -unwanted- effects).
anyway thank you for intant response!
Usually the B&W movies of yesteryears don't have much of scrolling end credits, if any at all. Most of them end with a 'The End', all lasting 2-3 frames. But yes, if you do have a B&W movie which has scrolling end credits, then you can't do end credits compression since you have already used up the option this way (you can if you *really* want to, but then it becomes complicated and you lose the benefit of 'Auto'GK).

This doesn't have any 'side effects' since all this option does is internally set values in the zone options in the XviD encoder dialog box as per the values you give here. And there is nothing wrong in using zone options for an entire encode in greyscale mode.

[Yo]

Originally posted by manono
Yes, you can add one of a number of AviSynth filters to the .avs.
Tweak(Sat=0)
Greyscale()
are 2 of them. Don't count on shrinking the video size very much, though.

Well, the purpose of doing that would be to shrink the video size. Otherwise there would be no point in doing so.

I don't think adding a greyscale filter would do the trick. The purpose of such a filter is to turn color video into greyscale, but I don't think it shrinks the file size at all. So, there would be no point in using one on video that is already greyscale. I think I once tried that, with a vdub greyscale filter, and the file size was actually larger than the non-filtered version. (I think Vdub is still saving it as a color movie, regardless of having gone through that filter.)

One would think that 256 shades greyscale would use up much less file space than millions of colors, so it could provide significant file size reduction, as it does with still photos. However, I cannot figure out if there is a way to really do that.

[manono]

Hi-

Otherwise there would be no point in doing so.

But plenty of B&W movie DVDs haven't been greyscaled, and have all kinds of rainbows and moire patterns remaining, especially on text or fine patterns. In addition, some filters you might use can also introduce color. Using something to greyscale it is always a good idea for B&W movies. But like I said, it won't help with your file size question, just get rid of the color.

[niamh]

Yo, I'm seeing double (http://forum.doom9.org/showthread.php?s=&threadid=80329)
Is this your annual thread? :p

[manono]

Deja vu all over again, in the immortal words of Yogi Berra. If Yo had paid attention to stickboy in the first place, we wouldn't be having this discussion now. I guess he either didn't believe what he read and wanted to get a second opinion, or forgot. Nice find, niamh.

is there a way to specify it as grayscale during encoding, and save on file size that way.

and then later:

The purpose of such a filter is to turn color video into greyscale, but I don't think it shrinks the file size at all

So, why did you ask a question to which you already knew the answer?

[niamh]

Nice find, niamh
:)

Well I knew there was a thread somewhere very similar to this one, "et pour cause", I'd posted in it ;). I just finally found it

[chilled]

ok thank you again for the non-unwanted seccondary effects stuff.
then reading both this and other one threads one (technical not practical) question remains:
why b/w movies are not many many much more compressible than color ones? specially if codec or a filter converts it to ACTUAL 256 shades (I knew b/w DVDs are in fact "color" sources -damn who the hell decided this?- that is the reason why I asked for an option to tell AGK to encode as b/w even if it finds small color artifacts in the source)

[len0x]

My speculation would be:

1) video is always encoding motion, i.e. difference between frames. No matter if its color or b&w the amount of motion is not going to go away.

2) Playback of RGB channels is not the same as storage of YUY2/YV12 data. I guess you always have maximum number of shades no matter what gamut is used (so its not 256 grey shades...)

*Edit* in fact now that I think of it - since b&w gamut seem to be much large than color one, it might be more difficult for codec to find edges of objects (remember that there is no "sharpness", there is only contrast) resulting in more blury and less compressible output...

[Yo]

Originally posted by manono

The purpose of such a filter is to turn color video into greyscale, but I don't think it shrinks the file size at all

So, why did you ask a question to which you already knew the answer? [/B]

No, I didn't ask a question to which I already knew the answer. There would be no point in doing so.

I said that I didn't think that using a greyscale filter would shrink the file size, as it would still be saved as a color video. I asked if there was a real way to save as a BW video, which one would assume WOULD create a much smaller file size, as it does with still photos. But I don't know of a way to do that with video, so I asked about it.

To those who complained that I might have written with a similar question years ago--I don't recall asking about this before, but it's quite possible. (There always seem to be those who want to "research" a person's posting history, to see if there is something that could be criticized.) If I wrote about the topic before, I see absolutely nothing wrong with asking about it again. (I guess if someone asked the same question every day, that would get rather tiresome, but asking a similar question a year later--what's the problem?) I obviously didn't figure out how to do it then, so I asked about it again now. There could be different people reading now, someone reading now who has an insightful answer into a question, who did not read the post with that question years ago. I see no problem with a question being posed more than once, even by the same person (as long as it's not TOO frequent! ;-) ). I really don't understand why a couple people made a big deal that in "researching" my posting history they found a similar question over a year ago.

To sum up the question--yes, I know there are filters (avisynth vdub, etc.) that will convert color video to greyscale. But if the video is still saved as color video, there will be no size savings, therefore, as has been discussed, using such a filter does not result in a smaller file size. However, I wondered if, as is the case with still photos, if one could actually SAVE video as grayscale, thereby significantly reducting file size, as occurs when saving still photos to greyscale. I don't know of a way to do this, and perhaps it is impossible. It seems like it "should" be possible, but perhaps no program will actually do it. Just asking.

[niamh]

I really don't understand why a couple people made a big deal that in "researching" my posting history they found a similar question over a year ago.

Take it easy will you. Obviously this applies to me, and I did not research your post history, but rather I spent some valuable time trying to dig out a thread that I knew existed to help you. Not my fault it's yours, and the answers are still valid.

Nothing stopped you from reviving that thread either, seeing that it's yours, rather than making a new one. Besides it has very interesting answers, I think :)

[chilled]

Len0x' speculations (sadly) sound right to my ears. damn.

[Yo]

Originally posted by chilled
Len0x' speculations (sadly) sound right to my ears. damn.

Yes, that is probably the case, since no one has come up with a way to save a BW movie as grayscale, saving a lot of space. Seems to be a major difference between video and still pictures.