encoding black/white source and/or converting to b/w

[phædrus]

Two questions, really.

First, when encoding a black-and-white source, can I reduce bitrate and still get the same clarity, since no bits would be needed for color info?

Second, there are a few color movies that I feel would work better in black-and-white. One noir film, The Grifters, I think would be best in B/W, and I also had the same feelings about Ronin. The last time I watched Ronin, I turned the color all the way down on the monitor, and I much prefer it. (The color is a bit washed out in the original anyway -- so I think they were going for a semi- black-and-white effect.) What filters should I consider to best render color films in black and white? I know there are some stock filters with VirtualDub that are supposed to do this kind of conversion. Is there anything special I need to know to use them?

And what percentage of bits will be saved by encoding a color source in black and white, versus color? Has anyone done any playing around with this kind of scenario?

I am a big fan of black and white in old movies anyway. I know most people aren't, but since I grew up doing a lot of black and white enlarging work in my Dad's photo darkroom, I have an ingrained fondness for it.

[gotaserena]

I'm surprised nobody answered to this one. For color > BW conversion, I recommend you taking a look at AVISynth, Greyscale and Tweak can do this.

In the uncompressed video throwing out the color information will save you 33% of space. In the YUV 4:2:0 space most of the DVDs come in the chroma has half of the resolution of luma. How the codec takes advantage of this fact is of course up to them.

[phædrus]

Thanks, gotaserena.

I am using AviSynth normally in my encoding. So I will look into those filters. I'm not familiar with Tweak. I'll look it up.

[AsTimeGoesBy]

Sorry, i haven't seen this post before.
At first i must say, i like b/w movies, but i have more colour films. Moreopver i don't use AviSynth.
But funny to see what you also own Ronin ;) - Indeed i never have had the idea to watch it as b/w...

Originally posted by phædrus
Two questions, really.
First, when encoding a black-and-white source, can I reduce bitrate and still get the same clarity, since no bits would be needed for color info?
...
And what percentage of bits will be saved by encoding a color source in black and white, versus color?
I could imagine that b/w would save some space due to more similar resp. redundant color values.
Of course you also should take into account that old b/w movies are low motion and often have noisy images.
So far, savings would sligtly dominate i guess, but hard to say how much that really is. But better make your own test samples.

But my b/w movies deserve generally the same bitrate as color movies. - Well, i like them of course, but this also has a perceptual aspect.
On color movies i guess my eyes suffer from a certain 'information overflow' caused by the many colours.
When watching b/w i am much more senisble to compression artefacts or blocks. I don't know why, maybe my eyes have more 'input capacity' in realtion to the (reduced) b/w content of the film.


Originally posted by phædrus
Second, there are a few color movies that I feel would work better in black-and-white. One noir film, The Grifters, I think would be best in B/W, and I also had the same feelings about Ronin. The last time I watched Ronin, I turned the color all the way down on the monitor, and I much prefer it. (The color is a bit washed out in the original anyway -- so I think they were going for a semi- black-and-white effect.) What filters should I consider to best render color films in black and white?
...
Well, what about a 'greyscale' filter?
My personal impression is that colour=>greyscaling requires adding more contrast (~10-20%) and reducing the brightness by 1-2%.
Indeed it would be very interesting to know how the greyscaling of a chosen filter really works and how many b/w colors will remain and how they are saved in DivX - i mean, it's 24bit format...

Belong my experiences you should also be aware that DivX often doesn't respect exaclty the bitrate you have set.

[Shinigami-Sama]

umm
8bit grayscale is equal to 32bit color so it would make sense that theres 24bits of color info nolonger needed and 24bit of color less each frame I would think would make a major diferance in the required bitrate
so lest me try and do thew math
8bits per pixel * 720xXXX = 184320xXXX
and the color vertion <GAH! still can't spell -.-'
32bits per pixel * 720xXXX = 3092376453120xXXX
seems like a bit differance to me
but I'm still fairly new to this...

[LordRPI]

Originally posted by AsTimeGoesBy

When watching b/w i am much more senisble to compression artefacts or blocks. I don't know why, maybe my eyes have more 'input capacity' in realtion to the (reduced) b/w content of the film.



It's generally that your eyes are more sensitivity to Luminance than Chrominance. Also, the lack of Chrominance probably lets your brain focus a bit more on what's actually going on.