pixels size and questions

[Lowtone]

Hello.

Since two years I am here and i am still wondering the same technical questions.
Mechanical television is from the analog paradigm; but nowaday we feed them with digital pictures.
In analog television, pixels are non square, but in digital pictures they are squared.
I am usigin the software called Premiere. It has plenty of pre defined formats, such as Pal or Ntsc or DVD or HDTV etc… and an interesting custom option.
I would be simplier to make videos in a smaller format. The reduced size and the reduced number of FPS is an advantage. The video files are small, and during the montage it uses less CPU ressources. Everything gets faster.
The only thing i knew was "32 line"
So 32 wide but how much tall is the picture ?
So there was the 3:2 aspect ratio. IF the pixels are square like in modern tvs; so the picture is 48 tall ( minus the synch it makes 45 )
So i spend one whole year to understand that ( that not mean i am dumb, but maybe slow or both )
Then i often thought that my pictures lacks of detail.
That year it was the death of analog transmitions in my country. So i speak with some people who likes television technical things like me and you, but more about things like SÉCAM, PAL, D2MAC, 819 line and those formats.
And i came to the concept of bandwith, wich i already knew well about audio stuff, and how it could increase the definition of worsen it. I also made some tests beetween VHS and SVHS tapes and compare them.

So now i am thinking back on NBTV stuff. The video2NBTV software didn't get the 32×48 videos right. So my videos in Premiere are twice the size.
I've noticed that the samplerate is 48㎑. As long as samplerate is related to bandwith, it could affects the picture.
I've tried to downsample a video to 44.1 and to 32. Yep the picture is a bit messed up and the synch is not always get right.
I made new testcards those days ( yes i really love testcards ) and try to make non square pixels .
If one pixel is 1 wide ( 1 line ) it is only 1/2 tall.
That makes 32×96 ( - synch = 90 ) and it seems to works quite right

SO

What if we change the sample rate of the software up to 96 ㎑ ?
Will the picture be amazing and have great details ?
How is it possible to make ?

[holtzman]

I do use version of Video2nbtv which provides 96 samplerate, it's on Gary's site some years already, named "alpha". Such samplerate is needed for 60 lines format signal. For 32 line signal, 96 kilosample rate is useless. There is no difference even between 41 and 48 kilosamples. However if you CONVERT digitally from 41 to 48 or reverse, there will be issues with quality.
I am sorry I am not good at explaining complex things and can not help you with further understanding the theory... I feel you confuse many things in terms of theory.
We never feed our mechanical tv with digital pictures, we just store the analog signal in digital formats. And there are no pixels at all in analog tv, only the line number and the shape of light spot which travels along these lines.

In Dominic Beesley player one can play with various aperture shapes, this illustrates very good how the shape of scanning hole affects the quality.
And if you convert to 60 line format with different samplerates and playback on this player, you can see how the picture gets crisp at 96 rate vs 48.

[Lowtone]

hello

However if you CONVERT digitally from 41 to 48 or reverse, there will be issues with quality.

So what i've expericend is the result of dithering i guess

We never feed our mechanical tv with digital pictures, we just store the analog signal in digital formats.

Yes but not everybody is filming and watching with all-analog or even mechnical tools. When using the software the pictures are digitalized.

And there are no pixels at all in analog tv, only the line number and the shape of light spot which travels along these lines.

Yes, i did't explain well what i meant.
When recording a VHS onto computer, the software asks for the resolution in order to convert the signal in pixels. So it has a number wich breaks the line signal into many pixels.
As long as i'm doing the montage in digital i was looking for this number, and i am trying to increase it. ( in order to play it back in with an analog signal inside the wire and to have more details per line )

I didn't try 60 line yet. But i really want to see 96㎑ on 32 line. It could ( maybe ) be a good way to store the files before converting to other formats.

[gary]

The video2NBTV software didn't get the 32×48 videos right.

In what sense do you mean it's not right? I can assure you it does create it in that aspect ratio, but keep in mind that it has to incorporate the line sync width also and those pixels are lost to the overall picture (of course).

Increasing the sample rate will NOT increase the resolution (or quality) because the NBTVA standard has a bandwidth of approximately 10kHz so 44.1kHz is already more than adequate to carry that.

Of course if you decide to create more vertical pixels (but maintain the picture aspect ratio) that is a different matter - but then it is NOT NBTVA standard.

[gary]

I didn't try 60 line yet. But i really want to see 96㎑ on 32 line. It could ( maybe ) be a good way to store the files before converting to other formats.

But surely if you are just storing it and then converting to other formats you are better off just storing it in it's original format? Or, if storing in digital form, digitising it to a format that maintains the original bandwidth.

[Lowtone]

Mmmm yes it is a good point !

In what sense do you mean it's not right?

When my AVI files are in 32x48, in many programms, like windows media player, or Video2NBTV, the picture is belived to be 4:3 format and is distorted. So i use 64x96 and it is nice.

I can assure you it does create it in that aspect ratio, but keep in mind that it has to incorporate the line sync width also and those pixels are lost to the overall picture (of course).

Yes, on my videos i put a "synch gard". It is a red line at the bottom, where i know no picture must be there. When processed in the software the pulses are on this bar, and this part of the picture becomes black.
Sometimes my MUTR kit loose the synch especially when the first line ( with no pulse ) is dark. So there i put some white pixels

Increasing the sample rate will NOT increase the resolution (or quality) because the NBTVA standard has a bandwidth of approximately 10kHz so 44.1kHz is already more than adequate to carry that.

Of course if you decide to create more vertical pixels (but maintain the picture aspect ratio) that is a different matter - but then it is NOT NBTVA standard.

Ah yes it would be different. But it is only for doing tests.

[gary]

When my AVI files are in 32x48, in many programms, like windows media player, or Video2NBTV, the picture is belived to be 4:3 format and is distorted. So i use 64x96 and it is nice.

aaaah I see, so it's the original video that's has the wrong aspect ratio?

Hmmm how are you creating the AVI?, you *should* be able to specify the aspect ratio so that DirectShow (which is the underlying system that renders the video) knows how to display it correctly, that is, it will still be in 4:3 aspect but there will be black bars either side of the actual image, and when Video2NBTV converts it only the image part will be extracted.

Could you post an example of one of your AVIs please?

[Lowtone]

When encoding i've specified the size 32×48 in 3:2 format. But most ( not all ) video softwares belives it is in 4:3. I have to check out if i still have those videos from two years ago. But it was in the good aspect ratio.
But anyway it is not a problem because the defition is better in 34×96 and every softwares plays it in 3:2.
When i process the files there are black bars on each side, and eveything is good and well ajusted.

[Klaas Robers]

And no mechanical monitor can display it.

[Lowtone]

It works on MUTR

[gary]

And no mechanical monitor can display it.

Klaas, I *think* what Lowtone means is that the video he is creating (an AVI video not NBTV video) is displayed with the wrong aspect ratio in the lefthand side window of Video2NBTV and this is, of course, then passed on to the subsequent NBTV video after conversion - it is still a valid NBTV signal but the picture is distorted either in height or width. He is therefore making a video with a different (wrong) aspect ratio, which is corrected by whatever is causing the distortion when replayed by Video2NBTV or other application that uses the MS DirectShow library.

A better solution would be to work out what is causing the distortion in the first place and fix that, but his method is a valid workaround, again, I *think*.

[Lowtone]

The 32×48 videos were distorted in width ( like when you have 4:3 on 16:9 tv and distorted option )
The 64×96 videos are fine. The vertical resolution is better thant 32×48 after converting in NBTVA standard.

With Premiere i could pan&scan videos and adapt them to the 3:2 format before converting.
I was trying to find the best way to produce videos for nbtv in digital, by making small files as close as possible to the format. My AVIs runs at 12.5 fps. I made them in colour but the software has no colour option. The NBSC software is not as easy to use ( load file *click* convert to wav )

The only problem i see is, when i play the WAV files through the Big Picture or NBSC player, sometimes the picture is not as accurate as the original.

[M3DVQ]

The vertical resolution is better thant 32×48 after converting in NBTVA standard.

If you're using video2nbtv then it can't be. Whatever video you input it crops out the contents of the zoom/pan rectangle and converts that to nbtva standard (32x48@12.5Hz)

[Lowtone]

so on this picture how can i have tiny lines on the right ? They are half a pixel high in 48 ( so 1 pixel in 96 )

[gary]

The 32×48 videos were distorted in width ( like when you have 4:3 on 16:9 tv and distorted option )
The 64×96 videos are fine. The vertical resolution is better thant 32×48 after converting in NBTVA standard.

Well I don't understand the width distortion because because 32x48 and 64x96 have the same aspect ratio, but yes, if you want to exceed the NBTVA bandwidth specification (9.6kHz) then the optimal video size would be 80x120 (for 48kHz). Note that if you use the Brown/Robers colour format (i.e. the current RELEASE version of video2NBTV) then the overall resolution WILL be constrained by the 10kHz smoothing filter (effectively 32x48) because it produces an NBTVA standard format. Not also though, that ideal size of the video would be 294x441 as the image will be resized to that anyway during conversion.

I was trying to find the best way to produce videos for nbtv in digital, by making small files as close as possible to the format.

Well, that will only work (for B/R colour format) IF the resizing algorithm used by Premiere is BETTER than that used by Video2NBTV (possible but unlikely) AND, and this is a big AND, the size of the image you produce is 294x441 because, whatever you put into it WILL be converted to that size prior to conversion. If it isn't then Video2NBTV's resizing algorithm will be used anyway, therefore removing any benefit gained by resizing with Premiere.

If you are using one of the Alpha release versions then the ideal size will be 80x120 because in that case no resizing will need to be done at all in the vertical direction (the image will converted to 32 x 120) and so the pixels in the vertical direction will be passed one for one to the NBTV video.

My AVIs runs at 12.5 fps.

It is *probably* a good idea to do that. Video2NBTV asks DirectShow to do the conversion from the videos native frame rate to 12.5 - I suspect that DirectShow doesn't do a particularly good job of that. If the frame rate presented to the NBTV conversion algorithm is NOT 12.5 then it will use a simple drop frame or duplicate frame algorithm to compensate.

The only problem i see is, when i play the WAV files through the Big Picture, sometimes the picture is not as accurate as the original.

Well it *should* be given the constraints given above.