DRA745: DISPC GAMMA LUT question

Hi Mike,

What is your usecase here? what are you trying to achiave?

Rgds,

Brijesh

Hi Brijesh,

We added gamma table support to our QNX display driver for a customer request.     When the system starts up the driver would attempt to calculate an initial gamma table based on 1.0 gamma.    Due to an error in the driver calculations some values were off by one causing some colors to be incorrect.  Although we're correcting that issue it raised the question that if gamma is 1.0 is there any reason to actually enable the gamma table or would it be more efficient to bypass the gamma table until the customer application sets a different gamma value.    

Thanks

Mike

Hi Mike,

Gamma table is 256 entry table for each color and it uses RGB component value as index into this table. Now the input component size is also 8bit, so yes it is possible to get 1 to 1 mapping.

Regards,
Brijesh

Hi Brijesh,

If a user requests 1:1 mapping is the same result achieved by disabling the gamma table as it would be by programming the 1:1 gamma table entries?

Thanks
Mike

Hi Mike,

I think so, but i have not validated it. As per TRM, it outputs 8bit for each color component for the given 8bit index. Table size is also 256 entries, so it looks possible.

Rgds,
brijesh

Hi Brijesh,

Thanks for your replies. From what I can tell disabling gamma_lut results in the same output as 1:1 but I was hoping for confirmation from TI to be sure.

Regards
Mike