PT_Playsound on newer cameras - General Discussion and Assistance - CHDK Forum
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PT_Playsound on newer cameras

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Offline reyalp

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PT_Playsound on newer cameras
« on: 21 / September / 2009, 20:33:23 »
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I've discovered that canon has changed the parameters to PT_Playsound.

CHDK expects it to take a short as a the first argument, as it does on say the a540:
Code: [Select]
MOV     R0, R0,LSL#16
MOV     R0, R0,LSR#16
STR     LR, [SP,#var_4]!
BL      sub_FFEBD248
MOV     R0, #0
LDR     PC, [SP],#arg_4

On newer cameras (a470, sd990, sx10 at least) it expects a pointer to a struct, where the first member is a short, and the second a pointer (a470 102c for example)
Code: [Select]
ADD     R1, R0, #4
STMFD   SP!, {R4,LR}
LDRH    R0, [R0]
LDR     R1, [R1]
BL      sub_FFC465F0
MOV     R0, #0
LDMFD   SP!, {R4,PC}
On the a470 at least, attempting to call it like the old function crashes. It probably does on the others too. (note that in SVN, this a470 port as another error, it points at the STMFD, which is not actually first instruction in the function!)

The function can be found on many cameras by
- look for the string "PT_Playsound"
- look for a pointer to that string.
- The pointer immediately following the pointer to the string is a pointer to the function.
In some cameras, the string and function may be directly referenced from code instead of being in a table.

It looks to me like the function called by PT_Playsound in the new cameras (sub_FFC465F0 above) may be equivalent to the old PT_Playsound. There are calls to it with familiar values.

If someone who has one of these cameras can figure out how to call it correctly, that would be helpful. I can make test builds if needed, but I need to know which camera. Otherwise, we should identify all the "new" cameras and nullsub this function.

Lesson:
Don't stop when you find the function with the right name, make sure it's actually the right function! (and yes, I'm guilty)
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Offline reyalp

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Re: PT_Playsound on newer cameras
« Reply #1 on: 28 / September / 2009, 22:16:58 »
It turns out that all the SX10 ports use the second function (i.e. not the one one associated with the PT_Playsound string, but the one called by that function) and this works, so I'll convert the other cameras to do the same.
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Offline reyalp

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Re: PT_Playsound on newer cameras
« Reply #2 on: 01 / October / 2009, 22:25:49 »
Checked in, changeset 811

Ended up adding a sig for PT_Playsound that works on newer dryos cams. The old function was too short to match.
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