Monday, September 6, 2010
This video is not remarkable for anything it shows, rather what it prevents us from seeing. I will use this, captured from the Olympic Challenger ROV #1 as an example. I recorded this just after 4:00AM CDT on 6 September 2010 directly off of BP's web site, and this is a straight screen capture, altered in no way.
The Oceaneering Millennium ROVs that BP is using for their surveys capture and send up via fiberoptic cable 1080-HD video. That is 1920x1080 pixels, with a full color range and with a full frame rate, which can range between 23.976-30 frames per second if using the standards set up by the ATSC committee.
This calculation will be rough but telling. Let's assume that the ROVs transmit video in a 16-bit colorspace that is the same as the normal mode of a modern PC. That is 16.7 million colors. If you take 1900 pixels width times 1080 pixels height, then multiply that by 16.7 million colors, then by 30 frames per second, you get 1.028052e^15, just over 1 quadrillion data elements per second. Again, this is very rough, since elements such as the video compression used by the ROVs is unknown -- this is assuming no compression, which will actually hurt the comparison in my calculations, but lets just go with that wrong assumption for the sake of ease.
The ROV video feed provided us by BP measures 320x240 pixels in dimension. Taking 320 * 240 and multiplying that by a guess of 32 greyscale levels per frame, and a frame rate of 15fps, we are seeing video which, again without compression, represents 36,864,000 data elements per second, or just under 37 million.
Let's divide the first figure by the second, i.e. the rough data rate of the video BP gets to see versus what they allow us to view. I am cheating and using Google as a scientific calculator since I don't have mine handy, but (1900*1080*16700000*30) / (320*240*32*15) = 27,887,695.3
That is correct -- assuming a 32-level effective greyscale "colorspace" and 15 frames per second in their tiny streaming window, the raw (uncompressed) data rate of the video that BP sees is almost 28 million times higher than that streamed to the public. Again, this is an extraordinarily rough number, but I am confident in its accuracy in terms of order of magnitude. The number of colors the ROV cameras can actually capture at that depth may be limited by the spectrum of light emitted by their floodlights, but there are other factors that would push the exact numbers even more towards my argument. Namely the compression being used, which is minimal between the ROV and mothership due to the high bandwidth afforded by their fiberoptic link, and incredibly higher between that original feed and what you and I see in our web browsers.
Modern digital video compression works on a psychovisual model, i.e. the codec throws away the bytes representing what it believes your eyes and brain are least likely to detect. So video compression, just like the compression in your MP3 audio files, minimizes file size, or in this case the streaming bandwidth, by casting aside the most intricate details to favor of the most noticeable.
All of this goes to say that the operators who drive BP's ROVs and the executives who give them their orders are able to view video which is of such immaculate quality as to be incomparable to what you and I get to behold. What we are allowed to see is literally a thumbnail of the real video, often with the colorspace greatly reduced or changed to greyscale, often with the aspect ratio distorted, always with a reduced framerate, and always with such high compression that we can often not read the on-screen superimposed data such as the date and time.
I'm not claiming that BP gets to see video which is literally 28 million times better than what we do, even though that's what the math says. But they are provided with video from their ROVs which is just as good as that which you see on Monday Night Football. If you don't believe me, view a rare publicly available video for yourself:
Be sure to select the 1080p option and maximize it to full screen or you won't see all that BP saw. That's right -- you can see individual scratches in the paint of their spewing well. The Department of Energy has these feeds, and BP has these feeds. But you and I are limited to viewing a tiny window of blocky, greyscale video like this one. Why? Not because BP is trying to save a few bucks on Internet bandwidth. Because they have things to hide. And have been quite effective in doing so.