John W <
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wrote in message I like Philips TVs - They look good, the remote is easy to use etc etc... but... I want a new 28 one with a decent amount ot teletext memory and none of the 50Hz models seem to have any... so I started to look at the 100Hz models - the Philips website make it nice and easy to find the manuals to download but they're all pretty useless so - does anyone know if the Philips 28PW9308C has a method of dropping back to a 50Hz mode if I find I can't live with the 100Hz pixel plus widescreen plus gizmos? I haven't downloaded that manual, but on my set (with similar chassis) you can switch of the 100Hz and picture processing. On pixel plus sets you can switch that off too. You may want to drop some of their processing (although the new pixel plus is very good), but I doubt you will want to turn off the 100Hz, which simply repaints all the screen twice as often from memory to remove flicker. (actual transmission is 50Hz interlaced). Ah - but that isn't what 100Hz TVs do - it certainly isn't as simple as just displaying the picture twice... Because 50Hz TV broadcasts are interlaced, and most 100Hz sets are also interlaced (if they were progressive they'd be running at very high scanning rates) if they simply repeated every _frame_ twice you'd get repeated motion on video material (as there is motion between the two 50Hz fields). If you simply repeated the fields twice you'd get exaggerated vertical resolution loss, and more visible line structure. What 100Hz TVs actually do is make up 2 new fields (or in some cases all 4 fields?) required to create a full 100Hz interlaced sequence from the 2 fields of the 50Hz source material. This is quite easy with film sourced material (which is often why DVD sourced films look good on 100Hz TVs) but much more difficult on video sourced material - especially that which contains fast motion. All 100Hz TVs also need to digitise the analogue video inputs (whether composite, S-video, component or RG
and store it in a _frame_ store. Early TVs only used 6 bit processing and 3:1:1 sampling - so the quality was truly awful. I would hope that all modern digital processing TVs now use at least 8bits and 4:2:2 sampling - though more bits should be used in the DSP that processes the picture. (10 bit sampling would be good - though I believe that all domestic MPEG2 kit works at 8 bits - extra sampling would reduce quantising noise on the repeated A/D and D/A conversions?) The common 100Hz artefacts are smearing or juddering on fast motion (especially credit crawls and rolls) It may reduce screen flicker - but it also quite significantly processes the picture as well. Personally I have yet to see a 100Hz set that I can watch without finding the processing artefacts _object_ionable - and I've looked at a lot. This is VERY annoying if you want a high-end set with a decent picture. Certainly Pixel Plus, DIST, DRC etc are all noticable reducing some aspects of the source picture quality - though they may superficially appear to improve other aspects. Steve
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