DVL-Digest 643 - Postings: Index Gyro Stabilisers? PAL to NTSC conversion Gyro Stabilisers? - "Perry" Erik Wolla posted: >Such gyros can be made from semiconductor micromachining, utilizing coriolis forces or other "regular" physics laws (masses, springs, etc.) There is no quantum physics involved in measuring the angular rate, except in signal post processing (transistors).< I thought I remembered reading once about the possibilities of using the actual spin of atomic particles as a gyro? Perry Mitchell Video Facilities http://www.perrybits.co.uk/ PAL to NTSC conversion - Perry Mitchell Kevin O'Hanlon wanted discussion on PAL to NTSC standards conversion: The process is actually pretty straight forward and there is nothing that you can do in hardware that you couldn't do equally well in software EXCEPT do it in real time! I'll describe the step by step process and then you can look at the resources of your software (or write something if you're a geek) and see how close you can get. After Effects does a pretty good job that will certainly match what you can get out of a top broadcast box without motion interpolation. Let us assume we are using component video. You first need to de-interlace the PAL video so that each field becomes a full frame of image information. You then need to increase the image size by 120%. Both these operations will soften the image a little, but the After Effect interpolation is excellent. Now the difficult bit, you need to generate 6 fields from each incoming 5 fields. There are two current ways to do this: 1) Supposing we start in sync at field 1, and we call the first PAL field fp1 and the first NTSC field fn1 (etc). fn1=fp1 fn2=(1/5xfp1)+(4/5xfp2) fn3=(2/5xfn2)+(3/5xfn3) fn4=(3/5xfn3)+(2/5xfn4) fn5=(4/5xfn4)+(1/5xfn5) fn6=fp5 In other words you mix the requisite proportions of the incoming fields to create the outgoing fields. Now in practice the relative speeds are not quite 5:6 because of the NTSC 29.93 frame rate, and the in/out videos will gradually drift. After Effects will do all this automatically if you simply put the NTSC video (correctly interpreted) into a PAL comp and turn on the frame blending. For more details see: http://www.btinternet.com/~perrybits/convert.html 2) The above method doesn't take into account image movement, so there is a rather juddery motion, especially on smooth pans and frame push effects. The BBC invented a system called motion interpolation where instead of just mixing fields, objects that move between the two field are 'in-betweened' and repositioned correctly. This obviously needs to be done on a pixel basis, and the device will need to have a certain 'intelligence' to know what is happening to the image. This is still very much a developing science, and nobody has yet developed a machine that is 100% reliable. Fast moving objects and ones that get obscured are obvious problems. The classic scenario is a golf ball disappearing behind a tree and coming out the other side as a leaf! Soccer has a particular problem with the ball travelling in front of the crowd with similar sized heads. For normal (non sports) material, the system can be very effective and is now almost universally used for broadcast transfers. Again, there is no reason why this couldn't be done in software, but I'm not aware of a specific product available right now. In terms of hardware, the basic conversion process (as in method 1) is now available for a lot less than it used to cost. The original BBC and subsequent ITN digital converters both cost 1,000,000+ but partly because they had to deal with composite video which in PAL has an 8 field sequence. The cost now is principally defined by the choice and quality of the interfacing to analog/digital video. I would think ,000 gets you a very nice broadcast quality box of tricks. The motion interpolation boxes from the likes of Snell & Wilcox are certainly in the ,000+ that Kevin mentioned. (diese posts stammen von der DV-L Mailingliste - THX to Adam Wilt and Perry Mitchell :-) [up] |
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