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  #21  
09-16-2017, 05:58 PM
jwillis84 jwillis84 is offline
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just a side thought..

I suppose we tend to think in (planar) storage format when [drawing] a line or a circle or sketching a scene.

Its not natural for us to think in terms of bit pumps and bit streams combining in a video encoder or decoder that goes on to paint fields and rasters.

So there has to be a way of converting from "frames" to "fields" or "lines" of video.

So (packed) or stringified bits streams of video versus (planar) or arrayed frames of video each have their place.

Having code that easily converts from one storage format to the other is important.

Building up pictures by adding and subtracting parts of lines, like working with clay from one line to the next.. sounds excrusiatingly "difficult" if possible at all for a human being. Animation artists typically work with a frame at a time, not a line at a time.

In reverse, converting from "native" line-based video format, which is inherently (liney) into a "progressive" frame-based video format.. like in computer image is just as difficult.. but without the advantage of automatic code libraries.. we have to "stitch" the frames back together.. and with interleve actually being two (different) frames separated in real time.. there is always a difference.

This exercise has helped me understand that de-interleaving is a "kind" of upsampling to get a higher resolution from fewer lines.

And there is [no] perfect upsampling method.. only acceptable artifacting

The best de-interleave .. is always (none) at all.. that is how the video was created, any change will by definition (be worse).. interleaving "works" due to persistence of the eye in the human brain.. and in a way your brain (is) the best "de-interleaver" if that's really how vision in a human being works at all.. we tend to filter out artifacting automatically all by ourselves.. and individually.. leaving it interleaved and presenting it that way.. lets each individual "de-interleave" in the manner that best suits them.

by the way, there is a really cool website that discusses the four CC formats interms of (packed) or (planar) formats

http://www.fourcc.org/yuv.php

its an easy read

the reason it is "four CC" is four characters take up 4 x 8 bits = 32 bits

A "megapixel" is a line "pixel" which uses four bytes to define its lumanance and color details, so if a pixel is defined by ARGB = 32 bits if its defined by UYVY = 32 bits, YUY2 = 32 bits

Its kind of elegant in that the "four CC" identifier for a format easily "fits" within the storage space of a single "megapixel"

If you don't know what the format of the video bits are, you can just snoop for one of the common four CC identifiers to tell you the video format.

Last edited by jwillis84; 09-16-2017 at 06:58 PM.
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  #22  
09-16-2017, 10:02 PM
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lordsmurf lordsmurf is offline
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Quote:
Originally Posted by jwillis84 View Post
I think he is making a distinction between DV (professional) and DV-AVI.
DV (professional) preserves more of the signal while DV-AVI throws away original color resolution.
It seems DV-AVI (which is consumer grade) makes some assumptions about your target viewing environment and decides for you that you don't need all that high color resolution.
DV vs. DV-AVI isn't correct.

AVI is just the container used with Windows. On Mac, it's Quicktime.

If you want to talk about the underlying codecs/compression:
- DV25 on MiniDV tapes (consumer "DV")
- DVCam (never really used)
- DVCPro25 (never really used)
- DVCPro50 (4:2:2 professional)
- DVCProP/HD (never really used)

So, essentially DV vs. DVC50, consumer vs pro.

The "throwing away" comes into play only when using the format for conversion, not shooting.

Quote:
Originally Posted by sanlyn View Post
Because PAL VHS is not 4:2:2 to begin with, capturing PAL analog to DV-AVI won't cost as far as color depth is concerned
That's not correct.

VHS is equivalent to 4:2:2, PAL or NTSC. In fact, PAL is actually better than NTSC.

PAL DV is 4:2:0 with variant co-siting to DVD-Video MPEG 4:2:0. Again, 4:1:1 was quartered, while 4:2:0 was alternating halved twice. PAL DV looks as good as a DVD-Video, which most people have no quality complaints over -- even picky ones. NTSC DV looks worse, especially viewed at modern 50"+ sizes. You can easily see the color artifacting and loss.

Quote:
Originally Posted by jwillis84 View Post
4:2:0 and the whole 4:2:2 or 4:1:1 sounds really interesting.
Remember these are ratios. Other formats can be 5:5:5, 3:3:3, etc. BetacamSP is 3:1:1

4:2:0 is confusing to most. It's actually more like 4:2/0:2/0. Or 4:2:0/4:0:2 alternating. Or 8:2:2. The important aspect is that the data is merely half (2). And even when sampled alternating, it's still better than quarter (1) of 4:1:1.

BTW, the Wikipedia interlace examples are garbage, but they fail to account for anti-aliasing. It mixes both colorspace and interlace artifacts, and pretends to be solely a colorspace artifacts. The progressive example applies to both properly deinterlaced and progressive.

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  #23  
09-16-2017, 10:43 PM
jwillis84 jwillis84 is offline
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Thanks Lordsmurf !

I was mildly curious about the DV formats, but too lazy.. or distracted to look them up.

Historically they sound interesting.. and obviously there is a lot more depth to them than I thought.

I certainly knew Sanlyn had a better grasp on them than myself.

PAL formats are also historically of interest to me.. but since everyone I know lives in the US or Canada.. a bit secondary in interest. I've always thought for whatever reason European, even Japan standards appeared superior. (I guessed it was because we had Legacy formats to contend with while they got to start with newer equipment and more choice).
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