get_live_histo

@reyalp @philmoz

I've just noticed a strangeness between the G5X and the G7X.

When using get_live_histo() on the G5X, my Lua script runs as expected.

When I run the the same script on the G7X, the get_live_histo doesn't seem to return any values, ie only 0.

As I say, identical code.

Do you have any insight/ideas as to why this should be?

Cheers

Garry

@pigeonhill


Does it return the histogram array where all the values are 0 or is it failing and not returning the histogram array at all?


If the latter then you might be running out of memory - get_live_histo can fail if there is no memory to allocate for a temp buffer.

I've just noticed a strangeness between the G5X and the G7X.

Just to clarify, you have G7 X II, not the original G7 X, correct?

edit:
You can use https://chdk.fandom.com/wiki/Lua/Lua_Reference#get_meminfo to check available memory.

I’m using the XIMR build and I have the g7X 100d.


The script inspects up to the top 10 bins of the get_live_histo, ie 245 to 255.


On the G5X the bins have non zero values when the image is over exposed.


The same script, on the g7X, with an over exposed image, returns zero in every inspected bin.

I’m using the XIMR build and I have the g7X 100d.


The script inspects up to the top 10 bins of the get_live_histo, ie 245 to 255.

G7 X mk1 is one of the cameras that uses less than the full 8 bits for the YUV buffer, with the full range being approximately 16 to 238

https://en.wikipedia.org/wiki/YUV#Relation_with_Y%E2%80%B2CbCr has some discussion of the variations

@reyalp

Thanks, I did not know that.

I’ll recode and report back when I can.

Cheers

Garry

@reyalp

Just did a quick test on the G7X and it looks like the highest bin that gets saturated is 235, ie rather than 255.

Many thanks for the education.

Cheers

Garry