
Processing the Page Turn - sohkamyung
http://www.cpushack.com/2017/09/30/processing-the-page-turn/
======
rwmj
The BBC's "Computer Originated World" is another sophisticated example of
this. One of them came up for sale a few years ago.
[https://en.wikipedia.org/wiki/Computer_Originated_World](https://en.wikipedia.org/wiki/Computer_Originated_World)
[http://625.uk.com/tv_logos/bbc1_85.htm](http://625.uk.com/tv_logos/bbc1_85.htm)

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javajosh
I must admit I do love these "when real men programmed with soldering
irons"-type posts on HN.

~~~
amelius
Yes, but I wonder what these people are using their skills for today, in this
age of apps.

~~~
kierank
Still selling overpriced broadcast hardware of course and trying as hard as
they can to make sure software can't enter their market.

~~~
zaphar
What a depressing and negative post.

I'm sure many of them moved on too designing even more impressive hardware and
chipsets to power even more impressive computational feats.

Or they may have taken those skills into the software development field,
creating complex and efficient software.

~~~
kierank
I'm sure many of them have done interesting things.

But the area I write software on in broadcast has a large number of these
engineers holding back progress, most of whom are close to retirement age and
now have heavy influence in standards bodies. For uncompressed video over IP
for example they propose insanely tight standards such as packets must arrive
within ~40us (that's us, not ms) of their allotted time, something very
difficult to reach in software. (I will be talking about this at demuxed next
week...)

They also insist that legacy artefacts from the analogue era must remain such
as VBI stay for another generation to save around 1ms of latency (and of
course their precious line buffers).

They are one reason the broadcast industry isn't able to move fast enough
compared to the web. As I've explained to them, some of us will have to deal
with the mess they have created in 40 years time.

~~~
paulmd
> packets must arrive within ~40us (that's us, not ms) of their allotted time,
> something very difficult to reach in software. (I will be talking about this
> at demuxed next week...)

Maybe in Ethernet-land, but this is trivially achievable (actually exceeded by
more than an order of magnitude) with off-the-shelf Infiniband gear that is
available for peanuts these days. Actually it's close to two orders of
magnitude if you want to shell out for the latest gear.

[https://en.wikipedia.org/wiki/InfiniBand#Performance](https://en.wikipedia.org/wiki/InfiniBand#Performance)

~~~
amelius
But does it actually provide a real-time guarantee?

~~~
paulmd
Yes. Adapter latency is guaranteed to be 0.5-5 usec depending on generation
(later revisions are faster+lower latency). Switches add about 170 nsec per
hop, plus whatever speed-of-light delays your cables add. 1 usec end-to-end is
realistic for modern gear.

[http://www.hpcadvisorycouncil.com/events/2014/swiss-
workshop...](http://www.hpcadvisorycouncil.com/events/2014/swiss-
workshop/presos/Day_1/1_Mellanox.pdf)

Of course with IP-over-IB you also need to factor in whatever latency is added
from your network stack, but Infiniband also supports RDMA so IB-aware
applications can essentially bypass this for high-performance or hard-real-
time usecases.

Basically, Infiniband takes the network out of the equation here. The
bottleneck then becomes how precisely you can time the software.

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miahi
For more TV effects boards, and the full devices (where these boards were
used) check the EEVblog teardowns:
[https://youtu.be/d9lZ2-a1P-E](https://youtu.be/d9lZ2-a1P-E)
[https://youtu.be/8ayBKoxX9Eg](https://youtu.be/8ayBKoxX9Eg)

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fulafel
> in 1989 there wasn’t a computer that could do this in near real time

Does this hold even if we consider the fastest computers, like Crays? A '89
Y-MP could do 2.7 GFLOPS or about 333 FLOPS per NTSC "pixel" in each NTSC
field. Smaller computers of the era might be more economical for the required
processing power, maybe one of the Thinking Machines SIMD MPPs?

~~~
userbinator
The demoscener in me disagrees with the statement entirely. ;-)

From the article:

 _It requires 3 inputs, the first video, the second video being turned to, and
a typically solid color /image that represents the back of the page_

This effect probably doesn't require that much processing power since all it
needs to do is switch (up to) twice on each scanline, from the pixels of A to
"back" to B; the switching points themselves can be calculated
straightforwardly since they vary linearly. Making the "back" itself be
another video doesn't add much extra processing. Here's a visual schematic of
one frame halfway through the effect (- = first video, + = second video, b =
back):

    
    
        ++++++++++++++++++++++++++++++
        ++++++++++++++++++++++++++++++
        ---------------+++++++++++++++
        ---------------b++++++++++++++
        ---------------bbb++++++++++++
        ...                        ...
        ---------------bbbbbb+++++++++
        ---------------bbbbbbbb+++++++
        ---------------bbbbbbbbbb+++++
        ---------------bbbbbbbbbbbb+++
        ------------------------------
    

As a rough guess, it's probably doable in around a dozen extra calculations
per scanline, which in NTSC is slightly less than 64us. Assuming (a very
generous) 100 clock cycles for those calculations, and hardware which has a
video mux so the software doesn't have to copy the pixels, that turns out to
require... slightly less than 1.6MHz.

Of course, if your hardware doesn't have a mux and you need to copy the pixels
between various buffers, then the requirement goes up around an order of
magnitude... but probably still doable on something like a 33MHz 386.

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mattnewport
Yeah, my thought reading the article was that an Amiga would probably be
capable of this effect. I feel like I've seen it some old demos in fact.

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zerohp
The Video Toaster add-on board did this, but it was a custom piece of
hardware. The video data never went through the CPU bus or memory.

~~~
jacobush
And the Video Toaster was NTSC only.

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fairpx
Fascinating. Anyone providing workshops/courses for complete beginners? Would
love to have my team (of UI designers) get to play around in this field for
inspiration sake. If you provide this stuff, please ping me (details in my
profile)

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wallabie
Would love to see the processing chip for the star wipe!

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puzzle
Bummer: I was expecting some reverse engineering of the specific algorithm
used by the board.

