Does uncompressed video have an associated colorspace?

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Postby Tab. » Mon Jun 02, 2003 3:10 pm

uh.. all distro codecs are YV12
YUY2/YV12 technically are forms of compression, but then so is interlacing. Not the same as perceptual or redundancy compression which is generally what we mean when we say compression nowadays. But even so YUV can be a completely non-compression based colorspace in 4:4:4.
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Postby the Black Monarch » Mon Jun 02, 2003 10:08 pm

YV12, YUV, YUY2, whatever, the point is that it's not RGB.

How the hell is interlacing a form of compression?
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Postby Tab. » Mon Jun 02, 2003 10:32 pm

hello. How do you make 60 fps in half the bandwidth? Interlacing. By playing on people's eyes the geniuses who invented television created a way to halve the horizontal resolution of the signal while still retaining a full picture and doing it at 60hz to boot. Like I said, not the same as we think of digital redundancy and perceptual coding, but compression nonetheless. Same with YUY2/12. Compression independent by nature, yet a form of compression itself. Store half to 1/4th the chroma resolution because the eyes don't detect it as clearly as opposed to the full chroma and luma signal. Similar to interlacing I suppose but color channel based and not entirely resolution based.
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Postby SS5_Majin_Bebi » Mon Jun 02, 2003 11:03 pm

Yeah.

What he said.
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Postby the Black Monarch » Thu Jun 05, 2003 4:07 am

Dude... turning 30 frames per second into 60 half-frames per second is NOT compression. Nothing is being compressed. Nothing is smaller after interlacing than before. The same amount of data is being used to describe the picture. The only thing that's changed is that the information is sent in more and smaller increments. That's like saying that you can compress a person by cutting him or her in half. Or that you can compress coarse sand by grinding it up into finer sand.

YUV colorspace is something that I never argued about with you, so don't act like I did.
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Postby koronoru » Thu Jun 05, 2003 11:50 am

the Black Monarch wrote:Dude... turning 30 frames per second into 60 half-frames per second is NOT compression. Nothing is being compressed. Nothing is smaller after interlacing than before. The same amount of data is being used to describe the picture.


With anime (which starts out at a lower frame rate anyway, typically 12fps), that's true. That's not the situation for which interlacing was invented, though. Interlacing was invented for live-action television, where the cameras take 60 samples per second (in order to reduce the flicker seen at low progressive refresh rates) and the signal only contains half the information from each one. It's not turning 30 into 60; it's turning 60 into 30, by throwing out half of each captured image. In a really real interlaced television signal, field 2 is not the second half of the same picture you saw in field 1; it is the second half of a picture that comes 1/60th of a second after the picture you saw half of in field 1. The pictures change with every field, and you only get to see half of each one.

That could be legitimately described as a primitive form of lossy compression, although to do so is pretty misleading in the AMV context because it makes it sound like the "interlacing" we might do on a computer (which involves re-ordering the data without throwing any out) somehow reduces the amount of data sent. When we deal with anime, there are far fewer than 60 picture updates per second, so we see each one in several fields, and interlacing doesn't throw out any data.
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Postby Tab. » Thu Jun 05, 2003 2:51 pm

thank you koronu

as for YUV I wasn't pointing it out to make it look like you were arguing it with me, I was pointing it out as a correlation to interlacing as compression since they're both different from the terms we think of compression in.
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Postby the Black Monarch » Mon Jun 09, 2003 5:31 am

koronoru wrote:In a really real interlaced television signal, field 2 is not the second half of the same picture you saw in field 1; it is the second half of a picture that comes 1/60th of a second after the picture you saw half of in field 1. The pictures change with every field, and you only get to see half of each one.


:shock: :?: :shock: :?: :shock: :?:

TV cameras shoot at 60 frames per second?

:?: :shock: :?: :shock: :?: :shock:

I find that hard to swallow...
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Postby trythil » Mon Jun 09, 2003 5:38 am

the Black Monarch wrote: :shock: :?: :shock: :?: :shock: :?:

TV cameras shoot at 60 frames per second?

:?: :shock: :?: :shock: :?: :shock:

I find that hard to swallow...


No, and that's not what koronoru said. With an interlaced-scan NTSC device, you do sample a signal 60 times a second, but you don't get 60 full frames a second.

With interlaced NTSC, you split up each frame into two sets of fields, and you send each set of fields every 1/60th of a second. On an interlaced device this gives you the illusion of 30fps motion.
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Postby the Black Monarch » Mon Jun 09, 2003 6:52 am

That's the way I thought it worked, but that's not what he said.
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Postby Tab. » Mon Jun 09, 2003 12:31 pm

try, no, it gives the illusion of 60fps motion and 480 lines of vertical resolution, which is what my point was the entire time. It's really 60fps of whatever x 240.
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Postby the Black Monarch » Mon Jun 09, 2003 5:37 pm

Tab. wrote:whatever x 240.


720.

dumbass nonsquare pixels.
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Postby Tab. » Mon Jun 09, 2003 9:48 pm

I said whatever because we're talking interlaced material, which could be broadcast (400some x 240/480), DVD (720 x 240/480), vhs (300some x 240/480), svcd/cvd (480/352x240/480) etc
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Postby JCD » Tue Jun 10, 2003 1:54 am

back to this...
the Black Monarch wrote:Yeah, but It's better than going through YV12 (DVD) -> YUV (Huffy) -> RGB (Premiere) -> YUV (huffy) -> RGB (Vdub) -> YUV (distro) bullshit. That's what I mean by avoiding SOME conversions.

just export uncompressed out of premiere and everything will be fine and you won't lose quality.
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Postby Tab. » Tue Jun 10, 2003 10:43 am

You only need one back and forth color conversion, and that's because of premiere's dumb ass. DVD (YV12) -> Premiere (RGB) -> Huffyuv (RGB) OR libavcodec's huffyuv / vble (yv12) -> distro codec (yv12)
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