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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

ProRes422, no 1080p???

Two questions:

1. What happens when an interlaced video hits a tv? I thought that no flat-panel tv is interlaced, so does a HD-tv de-interlace to separate frames?

2. Why the 1366x768 resolution of HD-ready (who makes these things up...) tv's since nothing is broadcasted in that resolution?

I don't live in a country with HD broadcasting so I am really confused.
 
Almost all Flat screens are truly progressive, usually they update at 60fps.
A deinterlace and framerate conversion is used on all of them.
How good that process is tends to follow the price of the panel.

Lately 48, 72, 75, 100 and 120hz screens have come to the market to support the native framerate instead. 120hz supports both 24p, 30p, 60p just by doubling the incoming frames

Note this is the framerate of the imageprocessor/buffer not the blanking of the screen which is very high frequency.

Allmost all 768 panels has 3% overscan, so even a 720p panel wont be 1:1 pixelmapped from a 720p source.
 
Anders Holck said:
Allmost all 768 panels has 3% overscan, so even a 720p panel wont be 1:1 pixelmapped from a 720p source.
Click to expand...

Which I believe is the only thing more asinine than the fact that they don't broadcast HD at a 1:1 ratio...:sick:
 
Isn't 3:1:1 the same as 4:1.33:1.33 , and therefore superior to 4:1:1 ?

No.
Full raster is 1920. HDCAM has 1440 luma samples, and 480 chroma samples (though I've heard 640 too so... I'm unsure).

*The exact meaning of the numbers is sometimes very ambiguous. For example, 4:2:2 DVCPRO is NOT the same as 4:2:2 Dbeta (or D-5). In DVCPRO, there are 1280luma samples and 640 chroma I believe.
 
Yes, and now they're trying to mandate a fixed overscan region too, which although I can see why you'd want an overscan, it really means that your pixels have been treated sloppily somewhere in the process.

Graeme
 
AFAIK, the correct definition of chroma sampling notation, according to Graeme and Poynton, is that the first number represents the recorded number of luma samples, and hence the 3 and 3:1:1 does not mean that the luma is 3/4 of the full amount, but that the 3:1:1 means that whatever the luma is, the chroma is 1/3 the resolution of it.

Graeme
 
I thought the x:y:z notation was to do with the ratio of the sampling frequency to the analogue luma bandwidth, ie 4:2:2 means that the luma is sampled at 4 times the luma bandwidth (2 x Nyquist) and the chroma at twice the luma bandwidth (as per Nyquist).

This is just from memory though. I am too lazy to look it up!
 
Originally the 4 did stand for the 4fs sampling system for luma bandwidth, but then they had the silly notion that therefor 4:2:2 in HD would be 22:11:11, and that was soon dropped. Quite frankly as there's no chroma subsampling notation governing body, there's no officialy definition.

For 3:1:1, I agree with Poynton who says that the 3 does not refer to 1440 being 3/4 of 1920, but that 480 is 1/3 of 1440.

Graeme
 
Graeme Nattress said:
<cut>

For 3:1:1, I agree with Poynton who says that the 3 does not refer to 1440 being 3/4 of 1920, but that 480 is 1/3 of 1440.

Graeme
Click to expand...

Which is what I was saying, 3:1:1 could also be written as 4:1.33:1.33:1.33

So 3:1:1 is not only higher quality than 4:1:1 but also than 4:2:0, which is used when refering to HDV for example, which is also 1440x1080.

Of course 1920x1080, compression or chroma subsampling aside, is superior to 1440x1080.

Cheers,
Damien
 
Sure you could write as 4:1.33 etc. So yes, it's a slightly higer chroma rate than DV's 4:1:1, but to declare it better, is like saying bad is slightly better than worse :-) 4:2:0 is fine for progressive, but horrible for interlace. Depends with which you're comparing.

Graeme
 
And if you think about it, 3:1:1 in 1440x1080 is actually pretty much equal to the chroma resolution of a 4:1:1 1920x1080 signal, when you compare the Chroma channels of the original HD-SDI input.
with the HD-SDI output.
I believe this was the reason Sony settled on 3:1:1 in the first place. 3x1.333333333 is very close to 4.
So the input subsampler would do a 1.3333333:1 reduction on the Y channel, and a a 2:1 reduction on the Chroma channels.
 
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