[opendtv] Re: Precision

Very Interesting!
In video domain is possible aliasing phenomenom?
For LP records nostalgia, Look this :
http://www.elpj.com/index.html



Jonas

In video, how much precision is enough?

Let us take audio as an example. Audio can be sampled at 48,000 samples per 
second, 16 bit, and it is "CD" quality. But sample at 192Khz at 24 bit, 
process, downconvert, encode, etc., and the quality is markedly better than 
when produced at the previously stated format. Of course, we are only dealing 
with one axis, representing pressure, and time (or are we?).

However, if we sample audio at 384Khz at 48 bits, I bet not but three people in 
the world could tell a difference from the audio produced at 192Khz at 24 bits. 
So there is a point to which we have human limitations and there is no reason 
to sample higher or with more "precision" (Law of diminishing returns), save 
research areas.

However, there is a weak link to this aforementioned audio recording: spatial 
offset. Even with 7.1 surround sound, there is still spatial gaps to fill with 
audio. So there is still room for improvement. But it is not in sampling 
frequency or bit depth that will make the difference.

Now back to video.

First of all, bit depth: 8 bit, 10 bit, 12 bit, higher? What is the graduation 
difference the eye can see at a particular wavelength? Obviously, it is going 
to be different at different wavelengths. So what is our target maximum? Or 
should it be different for different wavelengths?

I can clearly see a difference in each of the currently used bit depths; all 
are still well below the human's ability to perceive. The contrast range of the 
human eye is incredible.

I liked the papers that were recently presented about Color Gamut. Clearly 
there is progress in developing better displays and current production formats 
help deliver the quality for those displays.

Frame rates could improve. Temporally, we can perceive even changes at 1/60th 
of a second. When I did high speed photography, I was amazed at what my eye 
could see based on the effective shutter speed I needed to capture the image. 
Of course, to me it was a blur, but I knew it was there. Maybe, like the color 
gamut, the question is not what can be seen but what is the fastest object we 
are likely to capture on film, making that the maximum. But I would suggest 
that it could be in the order of 1,000 frames per second or more.

And then, there is peripheral vision and emersion effect. While IMAX does 
indeed cover a very large area, even in the optimal seating position, it is not 
optimal. I always liked OmniMAX better (where did they go?) because it covered 
more peripheral, although not all. And as soon as one looks to an object to one 
side, one sees border. Ultimately, one would need 360 degrees spherical, except 
maybe where the couch sits.

I am really am asking these questions so feel free to let me know if you know 
some of the target maximums. Like audio, I think there are some maximums where 
we can quit, but I don't think the current technology is there yet. I am just 
curious if anyone here knows what they are.

But one could still produce audio in 48Khz at 16 bit, process and encode, and 
still enjoy the music (or discussion, etc.). Almost anyone with normal ears can 
hear the difference but might not care, so long as the content is keeping our 
interest.

The same is most likely true of our High Def. formats today. After writing 
this, it does seem like there is a lot of room for improvement in the capturing 
and display of visual media.

Perhaps this is not really appropriate to OpenDTV so please feel free to 
disregard.

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