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How to use compression to change bit depth of a video signal?

jani12

Member
I need to use compression to change bit depth of a video signal.

Our Focal Plane Array(FPA) is Vanadium Oxide(VOx) Resistive Microbolometers Uncooled Thermal Infrared Detector. The output of this image sensor is 14-bit, Wide Dynamic Range(WDR), raw, monochrome, 640 x 480 resolution. The pixels of this video signal will be processed by Image Signal Processor(ISP). ISP input is 12-bits. Therefore, I need to compress FPA output to 12 bits and then input into ISP.

How to perform global tone mapping using two methods, PWL and LUT (curve defined by lut) based mapping. I need to tone map 14 bit data to 12 bit. What does PWL stand for? Please provide sufficient information so I can achieve this. It's suppose to be similar to gamma compression. I can do gamma correction in matlab. Can this tone mapping also be done in matlab? If yes, please provide some examples.
 

ronsimpson

Well-Known Member
Most Helpful Member
You have 14 wires from the sensor. You will only use the top 12 wires. That is simple.

I think you will want better than that.
Run all 14 bits into the FPGA. Get one with memory!! Maybe even dual port memory.
The memory has 14 address lines to (2^14) memory locations.
The memory has 12 bit wide data.
On your PC you can draw graphs of different type of correction and load into the memory.

Is this a school project? A work project? From your questions I can see you do not understand why you need to do this.
 

jani12

Member
>> On your PC you can draw graphs of different type of correction and load into the memory.
Please provide examples for my application.

This is work project. I need to do this because Image Signal Processor(ISP) doesn't accept 14-bit inputs. It accepts 12-bit inputs.
 

ronsimpson

Well-Known Member
Most Helpful Member
Example
1555002740894.png
Corrections are done for many reasons. One example is; If you are looking at your monitor in a very dark room you can see brightness level 1,2,3... but in a bright room the first 50 levels are missing. So in your table you can make level 1 on the input side become level 50 on the output side. It is common to have a "black level" adjustment that sets where black is. And have a "white level" adjustment to the brightest picture does not hurt your eyes.

It is simple to not use two bits because of your "12-bit ISP" but your lookup table will work better if you use all 14 bits in the table.
 

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