Quote:
Originally Posted by ferix
Hmm... tell me more...  |
If You look at the typical AFE (Analog Front End) for video monitors:
http://www.analog.com/en/audiovideo-...s/product.html
(this one is modern due of HDMI with HDCP support but there is lot of older IMO even easier to use - more available documentation)
, there is lot of registers in such AFE (usually AFE is together with ADC) - there is part related to the clock recovery (ADC trying to sample video signal with exactly same frequency as video is produced in source), sync extraction (most of AFE is equipped with some auto sync detection - You only need to specify group of video standards for search - ie H and V sync range). main problem for monitors is that they support on VGA only typical and common modes for PC world even if hardware is fully capable to acquire whole range of lower standards. Monitor manufactures simply don't use this functionality - limitation is related to software (firmware) for monitor not hardware of monitor - this can be easily seen for LCD monitors that are equipped with SCART connector - they use exactly same electronics as VGA but if You switch to SCART they simply run register settings for AFE that allow to sync and recover clock from TV video standard.
So whole tweaking for LCD which not support anything bellow 30kHz is to switch (ie reprogram) registers in AFE in that way that this support 15kHz, second , this must be done in that way that allow next part of monitor to rescale sampled data to native LCD size.
best is modify original firmware for monitor that whole monitor began work with everything bellow 30kHz - still it can be made due of this that lot of monitors have firmware in some kind of flash and can be reprogrammed.
So idea is simple but... real life can be more complicated but IMO is better to do software modification in LCD than redesign H circuitry in CRT.