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Graceful Degradation Is Good

When I wrote my previous blogs about digital cameras and noise (see “Related posts” below) I was not really thinking about it in terms of analog or digital being better. It was just an example of the two systems working together in a cooperative manner to solve a problem.

Yes, I love the fact that the pictures are stored digitally in memory rather than relying on film, but I had naturally accepted that analog components were necessary in such a system. I am not aware of any research related to being able to turn images directly into a digital stream of data — and even that would need to have some analog side to it.

So, I was surprised by one of the comments that I received from one “NetCrawl” that started by saying “Digital system[s] really solve the noise problem.”

Now, NetCrawl had not had the advantage of seeing part two of that blog where I show that digital processing actually injects noise, but it did get me to thinking about this problem in a little more detail. First, I have no issue at all with noise in photography. It has always been there and, as “artists,” we are expected to overcome the limitations of the materials and physics as best we can. It can lead to creativity.

The same is true with the manufacturing of semiconductors. We use masks to create the silicon IC. The random variation in the fabrication process is inherently noisy, and we find ways in which we can reduce the noise because that leads to higher yield.

Then my girlfriend's car broke down, just as we were about to go away on a trip. Without going into all of the details, it appears that a body control computer had a problem. This in turn led it to send a message to the engine control unit making it think the car was being stolen… so it disabled the ignition system. As you can imagine, this led to the car being towed back to its starting point.

I used to love tinkering with cars — they were analog. If things were slightly off, it would still run, just not perfectly. You could tune it, upgrade pieces of it, and life was good.

Now I feel helpless when I look into the engine compartment. The analog bits are gone — with the exception of the combustion chamber itself — all in the name of progress. This system cannot degrade gracefully; it fails in a digital manner. It goes by itself, or it is towed. There is no middle ground. At this point you may be thinking that I have become a convert and that I will stray over to the analog side. Not so fast.

So, back to my camera and the “problem” of noise. It is not a problem that my camera has noise. I am very grateful for those analog components that degrade slowly in their performance. Think about this in a totally digital camera — it would probably tell me there was insufficient light to take the shot. It could either take a perfect image or none at all. My advice to Canon may well be — skip the traditional ISO numbers if you cannot support them in the analog amplifiers, and so guide me to the less noisy settings.

So, the next time you are designing a product where there are choices that can be made in the analog/digital divide, I ask you to consider how many people would appreciate a slowly degrading system rather than a binary operation. Even a digital person can appreciate the analog components. Are there products where you think the analog/digital divide has been put in the wrong place?

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13 comments on “Graceful Degradation Is Good

  1. Vishal Prajapati
    July 29, 2013

    There is a similar case with the LED and LCD TVs. Earlier in analog TVs if there is some problem in the circuit, it would show picture with somewhat smaller size or there would be some picture clipping, but it would still continue to show some thing. Now in case of LEDs and LCDs either it shows complete picutre or it doesn't show.

     

    Similar in case of DTH also. Earlier with analog coaxial transmission, the picture would be shown with lot of noise in video and audio but in case of DTH as soon as rain starts, it stops showing anything other than warning on the screen.

  2. goafrit2
    July 29, 2013

    >> So, the next time you are designing a product where there are choices that can be made in the analog/digital divide, I ask you to consider how many people would appreciate a slowly degrading system rather than a binary operation.

    You are correct – those in the business of neuromorphic engineering utilize that feature a lot. You need some elements of chaos to model the ways neurons and synapses work. And they build on spiking communication and never digital.

  3. Brad_Albing
    July 30, 2013

    As noted by VP, digital video transmission (HDTV in this country) is subject to the all or nothing phenomena.

  4. Brad_Albing
    July 30, 2013

    Which reminds me – when I was a kid, one of my favorite geeky hobbies in the summer was to surk thru my VHF TV channels looking for DX reception. Now, ain't gonna happen.

  5. BrianBailey
    July 30, 2013

    Well, that is not quite true. If the signal is so weak, then you are right, but there can be noise in the signal which results in tearing and takes a while to get corrected because each frame builds on the previous one rather than every frame being sent in totality. Thgis of course is why the bandwidth requirements are so much smaller. But there is a complete frame sent out at intervals which gives it a chance to start afresh.

  6. Brad_Albing
    July 31, 2013

    Ah – so that's how that's done – I was wondering about the means and methods. Thanks.

  7. Vishal Prajapati
    July 31, 2013

    That's the point sir. We need to wait for the next whole frame to be transmitted. Untill then for half second or second we can't see the next updated picture. That means we miss lot of frames during that correction period. While in case of analog TV we don't miss any frame due to noice. The noice just appears as a white or black spots in the raster. But can't miss a single frame.

  8. BrianBailey
    July 31, 2013

    I am not disagreeing with you. This was the point of the whole article. If you assume that there will be no dropout, then digital is making a good set of choice to maximize the bandwidth, but the price you pay is that period of messed up picture if noise is injected into the system. What would a good compromise be? I am not sure there is an analog equivalent where only changes are sent. Without the quantization of digital, analog would see too much as having changed. Maybe each pixel or group of pixels would have to be put through a threshold detector to see if they have changed enough to be worth resending.

  9. Etmax
    August 1, 2013

    I'm not sure I can entirely agree with you, firstly there are any number of ways that the parts of a car can fail digitally as I have experienced a number of times, I think in this case it is more to the point that the macro components of a traditional car were repairable with a bit of ingenuity where as if the ECU fails you're on your own. My modern car recently was failing gracefully, in that the throttle position sensor (TPS) was faulty and yet I could still drive ther was just not much acceleration. If the throttle linkage on a traditional car broke (the mechanical analogy) it would have been a digital failure. Most things on a modern car have digital work arounds and the car DOES keep running if not as well and a light comes on to tell you it's on its way out if you're not perceptive enough to notice the performance change. That's not say it's easy to notice, it actually took me 2 months to realise the TPS was faulty. I could go on with many examples like when the old Honda I had wore out the alternator brushes the car simply stopped shortly afterwards and I only look at the dash light at ignition on typically.

    Comparing digital transmission against analogue (TV) the digital cliff is often mentioned, and this one is also graceful, as the signal degrades the analogue equipment introduces ever more snow until you can't see anything, where as with digital the snow and ghosting even can be so bad that the analoque TV would have no picture but the digital still has a perfect picture. A little bit weaker and the digital TV starts to have the odd MPG block appear on the screen and this gets successively worse until the picture is unwatchable so here again we have graceful degradation in digital. If you look at the French 819 line TV standard (analogue) because the picture was FM transmitted it actually behaved a lot like what digital is criticised of namely a relatively abrupt interuption to the image while being entirely analogue.

    In cameras, as you've mentioned there has to be some analogue as a camera interfaces to an analogue world, but the lack of graceful degradation you mentioned is unigue some cameras only, as it's a SW design choice the manufacturer made and not really limited to digital cameras as the scenario is possible that an analogue camera could not take pictures if the light levels were low (although I know of no examples of such a camera).

    So really, I think it's more a reflection of designers choices and not anything that is entirely analogue vs. digital.

     

  10. Etmax
    August 1, 2013

    🙂 it actually can, only the picture may seem so good that you wouldn't know the signal was DX. Digital TV is so good at recovering pictures from the noise that a signal that is almost all snow can actually appear crystal clear (some times). Think about the transmissions coming in from the 2 Voyager probes, that's digitally encoded and they transmit with 23W from 11billion km away. Now that's DX, and they send pictures 🙂

  11. BrianBailey
    August 1, 2013

    I am guessing that the throttle position sensor was analog. In many cases, and you mention some, the analog part can degrade slowly and oftenm unnoticed. It will then reach a digital breaking point where it has gone so far out of alignment or range that it just cannot operate anymore. A cable is an analog connection. It can stretch, fray and these can eventually lead to failure. The point where it is connected to something can break and yes this is a digital failure.

    Perhaps it is better to thing in terms of slow, gradual degradation rather than assigning them as being analog or digital and yes, I agree software and system design are very important elements to ensure the system operates as long as poibble without failing.

  12. Etmax
    August 1, 2013

    Yes, that's true at the level where the whole I-frame is lost, but this isn't always the case, I regularly see the block size increase on weak signals and this gets progessively worse until your scenario comes in. This does of course depend on the SW implementation as to whether you see the degradation or it simply shows the lost signal message.

  13. Etmax
    August 1, 2013

    The TPS can actually fail completely and the car still runs. TPS is used mostly for predictive behaviour which is why rapid acceleration was affected. Because I don't accelerate rapidly frequently it took a while to notice. This is an example of a “digital” failure of an analogue component resulting in graceful degradation of the system.

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