I was trying to convert my camera (A570IS) to kind of portable movie player, and for this I need both A/V out and LCD enabled (to insert headphones), which is normally imposible, BUT with CHDK nothing is impossible. This is result of my search through memory and firmware is shown on this movie:
http://www.volny.cz/shali/DSCF3468.AVI(sorry about quality, I must use my extremely old FinePix camera to shot this, and it even don't record sound)
On this movie, you can see what is happening - I'm playing video on TV using A/V out, then press ALT and +/- button to start my function, TV goes blank, LCD turns white and after a second video is playing on LCD (sound is still going to TV).
What did I do:
* write 0x00209CC0 at addr. 0xc0220214 - I found this out by comparing special memory dumps when A/V connected and not-connected.
* write 0x0000F8F0 at addr. 0xc0910080 - described somewhere else on the forum, control LCD backlight
* wait one second - smaller time is probably needed, meanwhile TV goes off, LCD goes on and show white
* call function at 0xFFDDA430 with parameter 0 - this enables showing screen on LCD. Sorry but this function doesn't have name in IDA (its called sub_FFDDA430), at least when using current signature file.
MAJOR DRAWBACKS:
* You can see some white and black strips on left of the LCD (better on this photo:
http://www.volny.cz/shali/DSCF3470.JPG) and the picture is slightly stretched so its height is bigger.
* You can only view videos - attemp to show photo of any size is shown at the end of the movie - the camera shuts itself down.
* I tested it only on A570IS - memory locations probably vary on other models.
So conclusion - it IS POSSIBLE to watch movie on camera with amplified headphones on, but it will need someone who know ARM / IDA / everything better than I to make this a real part of CHDK.
