Grayscale Encoding for B&W/Colour Movies?

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ozmosis82
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Grayscale Encoding for B&W/Colour Movies?

Post by ozmosis82 »

If I were to encode films that have a fair amount of both black & white and colour scenes, should I activate grayscale encoding? I'm thinking of films like American History X and Pleasantville.

hawkman
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Post by hawkman »

Then it'll all be black and white, AFAIK, which is probably not what you're after.

PuzZLeR
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Post by PuzZLeR »

Grayscale encoding is actually more of an editor/MPEG-2 encoder type of thing, before the MPEG-4/Xvid/H.264 encoding stage. And it's actually a filter that will affect the quality and may slow down the process. Use it ONLY if you specifically want something in black and white that ISN'T black and white.

Otherwise, under normal circumstances, where you just want to encode a movie/film/etc. and you just want to compress and create a file in .mp4 that has as much of the original quality possible, then DON'T click on grayscale encoding - even for black and white video.

jbrjake
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Post by jbrjake »

PuzZLeR wrote:Otherwise, under normal circumstances, where you just want to encode a movie/film/etc. and you just want to compress and create a file in .mp4 that has as much of the original quality possible, then DON'T click on grayscale encoding - even for black and white video.
Well what I've always heard is that A: it should be used on black and white movies to get rid of a green tinge and/or rainbow-colored shimmering, and that B: grayscale encoding, or at least the way it works in HB, has no affect on x264.

PuzZLeR
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Post by PuzZLeR »

Hey jbrjake,
A: it should be used on black and white movies to get rid of a green tinge and/or rainbow-colored shimmering
I think I know what you mean, but are we talking about a green tinge that was already on the B&W movie BEFORE encoding? Yes, I've seen it, and being a purist, decide to keep it even after encoding. I'm one of those that likes to emulate the original as close as possible and consider the "quirks" part of the film. But, to each his/her own... :) Now if you're talking about that green tinge only AFTER encoding, even though I personally haven't noticed (yet), you do have a point. Then I would recommend grayscale (and go see an eye doctor :wink:)
B: grayscale encoding, or at least the way it works in HB, has no affect on x264.
Didn't mean it affects x264. Meant it's like one of those editing type of special effects that you can do before encoding. Isn't it actually a "filter" in essense? If it is, then when I said it will "affect the quality" I meant it would change it like any other filter does - either "perceptively better" or worse.

saintdev
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Post by saintdev »

All HB's grayscale option does it to remove the U and V planes from the image, leaving the Y plane. In effect all it does is to Remove the color from the image without affecting the detail (the U and V planes contain less detail than the Y plane to start out with).

ozmosis82
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Post by ozmosis82 »

Awesome. Thanks for the advice gang!

PuzZLeR
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Post by PuzZLeR »

saintdev wrote:All HB's grayscale option does it to remove the U and V planes from the image, leaving the Y plane. In effect all it does is to Remove the color from the image without affecting the detail (the U and V planes contain less detail than the Y plane to start out with).
Thanks for the explanation. But I'm still correct in saying that you "affect quality". You're still "removing" something nevetheless. In theory, it DOES remove quality - the quality that contains COLOR. But in this case, this would be a "quality" that you would actually WANT removed... so only in practice you are not affecting quality... My brain hurts now... :cry:

Eug
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Re:

Post by Eug »

jbrjake wrote:Well what I've always heard is that A: it should be used on black and white movies to get rid of a green tinge and/or rainbow-colored shimmering, and that B: grayscale encoding, or at least the way it works in HB, has no affect on x264.
saintdev wrote:All HB's grayscale option does it to remove the U and V planes from the image, leaving the Y plane. In effect all it does is to Remove the color from the image without affecting the detail (the U and V planes contain less detail than the Y plane to start out with).
So does turning this on does NOT improve encoding efficiency for H.264? (It'd be nice to be able to reduce the bitrate for H.264 B&W movies, to save space.)

I'm trying to reconcile jbrjake's post with saintdev's. The UV planes have a fair amount of (potentially unnecessary) information that is being discarded, but I don't claim to understand how H.264 works with B&W video. Or is Handbrake simply ignoring the flag for H.264?

saintdev
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Re: Re:

Post by saintdev »

Eug wrote:I'm trying to reconcile jbrjake's post with saintdev's. The UV planes have a fair amount of (potentially unnecessary) information that is being discarded, but I don't claim to understand how H.264 works with B&W video. Or is Handbrake simply ignoring the flag for H.264?
H.264 does have a grayscale mode, it is not implemented in x264. Dark Shiarki tried it, but gave up because it only gave a very small increase in efficenty (ie: less than 0.01%).

rhester
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Re: Grayscale Encoding for B&W/Colour Movies?

Post by rhester »

In my experience, greyscale encoding actually increases bitrate requirements, presumably due to the sharper edges (and the fact that true black-and-white content tends to have a higher degree of grain/noise).

Rodney

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