Squeaky Chipboard what to do before tiling? - Tile Advice

[theandroids]

Hello again guys, Took up all my laminate and the floor is pretty iffy, obviously done by cowboys.
Some parts are not level which I'm told I can level those parts with 'thin set' also is very squeaky but not that bouncy. How would I get rid of the squeakiness?
What is the best course of action. Would you just put down 'No more ply' and tile or should I do something to get rid of the noise first. I just don't want the tiles to crack more than anything else. X marks the squeaky spots. The tiles are 600 x 600 porcelain.

 

[LM]

The noise is coming from the chipboard moving and rubbing against the nails most likely. It needs to be screwed down solid to the joists then see if there is still noise. There is a risk of pipe work running close to the floor if there has been a lazy plumber who hasn't ran the pipe work lower down through the joists, I've seen that several times, so consider that also. Once the noise issue has been resolved overboard the floor with the No More Ply.

 

[theandroids]

The noise is coming from the chipboard moving and rubbing against the nails most likely. It needs to be screwed down solid to the joists then see if there is still noise. There is a risk of pipe work running close to the floor if there has been a lazy plumber who hasn't ran the pipe work lower down through the joists, I've seen that several times, so consider that also. Once the noise issue has been resolved overboard the floor with the No More Ply.

I'm dreading its a complete mess under that floor, the people who built the place did a poor job all round so I doubt its pretty under there. Here is a pic which I marked out the layout a nails in white. Looks awful. nails are just put anywhere by the looks of it. What way do you think the joist is running?
Only thing with no more ply is it would add too much height. Do you think dirta would be fine instead straight on top of this chipboard?

 

[LM]

It looks like the joists are running across the floor from left to right of the picture.
Ditra stuck down with Ardex AF200 would be fine provided the floor has no diflection and is screwd to the joists.