# US 12,192,645 B2 · Method and circuitry for exposure compensation applied to high dynamic range video

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- Number: US 12,192,645 B2
- Document ID: US12192645B2
- Status: Granted
- Kind: B2
- Application number: 18/098,175
- Filed: 2023-01-18
- Published: 2023-07-27
- Granted: 2025-01-07
- Earliest claimed: 2022-01-26
- Assignees: Realtek Semiconductor Corp.
- Applicants: Realtek Semiconductor Corp.
- Inventors: Yu-Heng Tzeng
- Web page: https://patentgrep.com/patent/US12192645B2

## CPC

- H04N 23/73: by influencing the exposure time
- G06T 5/50: using two or more images, e.g. averaging or subtraction
- G06T 5/94: based on local image properties, e.g. for local contrast enhancement
- G06V 10/25: Determination of region of interest [ROI] or a volume of interest [VOI]
- G06V 10/507: {Summing image-intensity values; Histogram projection analysis}
- G06V 10/60: relating to illumination properties, e.g. using a reflectance or lighting model
- G06V 10/751: {Comparing pixel values or logical combinations thereof, or feature values having positional relevance, e.g. template matching}
- H04N 23/741: by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
- H04N 23/743: Bracketing, i.e. taking a series of images with varying exposure conditions
- H04N 25/589: with different integration times, e.g. short and long exposures
- G06T 2207/10016: Video; Image sequence
- G06T 2207/10144: Varying exposure
- G06T 2207/20208: High dynamic range [HDR] image processing
- G06T 2207/20221: Image fusion; Image merging
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING

## Abstract

A method and a circuitry for exposure compensation applied to a high dynamic range video are provided. The circuitry is adapted to an image-acquisition device. In the method, when a video is received, the pixel values for each of the sequential frames can be obtained. Next, an exposure value ratio between two adjacent frames is obtained. A processor exposure value ratio of an image signal processor can be regarded as an initial exposure value ratio. A fixed adjustment ratio is used to control the image signal processor and an image sensor of the image-acquirement device so as to calculate an exposure value ratio for each of the frames. The exposure value ratio is referred to for performing the high dynamic range compensation for the frames so as to output an HDR video.

## Claims

### Claim 1

A method, comprising:
retrieving pixel values of pixels in each frame of sequential frames of a video;
obtaining an instant exposure value ratio, in units of a row of one of the frames, between two frames in succession among the sequential frames by comparing sums of row pixel values of two of the sequential frames;
acquiring an exposure value ratio for each frame of the sequential frames in real time by using a fixed adjustment ratio to control an image signal processor and an image sensor according to a processor exposure value ratio of the image signal processor, wherein the fixed adjustment ratio is used as a fixed ratio to fine-tune the exposure value ratio for each frame so as to control each frame to have a same error, and the instant exposure value ratio of a first row of one of the frames is used as the processor exposure value ratio to be inputted to the image signal processor; and
generating sequential frames that undergone a high dynamic range compensation process by exposure compensation that employs the exposure value ratio for each frame of the sequential frames.

### Claim 2 (depends on 1)

The method according to claim 1, wherein, in a beginning of the method, a brightness range threshold is set for excluding overly-dark and overly-bright pixels, and a light-dark ratio threshold is set for excluding one or more potential moving regions from the video.

### Claim 3 (depends on 2)

The method according to claim 2, wherein, in the method, two frame exposure values are provided in a high dynamic range process; wherein, when the sequential frames are retrieved from the video, a first frame exposure value ratio is used as the processor exposure value ratio that multiplies the fixed adjustment ratio, and a second frame exposure value ratio is used as the processor exposure that multiplies twice the fixed adjustment ratio; correspondingly, an initial exposure value ratio that corresponds to the first frame exposure value ratio is set in the image sensor, [an] the error is adjusted to be the same as the fixed adjustment ratio, and the exposure value ratio corresponding to the second frame exposure value ratio set in the image sensor is a result of the initial exposure value ratio multiplying the fixed adjustment ratio.

### Claim 4 (depends on 2)

The method according to claim 2, wherein, when pixel values of two sequential frames are retrieved from the video, a ratio range and an appropriate brightness range are set between the two sequential frames according to the processor exposure value ratio and the brightness range threshold for selecting a valid pixel pair between the two sequential frames within a reasonable ratio after excluding overexposed or overly-dark pixels, and an exposure compensation is performed upon the HDR video with the valid pixel pair between the two sequential frames.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the instant exposure value ratio equals to a previous row exposure value ratio plus an adjustment value for each of the rows.

### Claim 6 (depends on 5)

The method according to claim 5, wherein, when the exposure value ratio for each row of each of the frames is calculated, a threshold for adjusting the exposure value ratio is used to converge the exposure value ratio for each of the frames.

### Claim 7 (depends on 6)

The method according to claim 6, wherein, starting from the processor exposure value ratio initially, the adjustment value of each of the rows and the fixed adjustment ratio are used to converge the exposure value ratio, a removable region with a height in each of the frames is removed after the convergence, and an output image region with another height is taken for outputting the HDR video via an output circuit.

### Claim 8

A circuitry for exposure compensation applied to a high dynamic range (HDR) video, the circuitry being disposed in an image-acquisition device, comprising:
a control circuit used to control operations of an image signal processor and an image sensor of the image-acquisition device, performing a method for exposure compensation applied to a high dynamic range video including:
receiving a video, and retrieving pixel values of each frame of sequential frames of the video;
obtaining an instant exposure value ratio, in units of a row of one of the frames, between two frames of the sequential frames by comparing sums of row pixel values of two of the sequential frames;
using a fixed adjustment ratio to control the image signal processor and the image sensor according to a processor exposure value ratio of the image signal processor for acquiring an exposure value ratio for each frame of the sequential frames in real time, wherein the fixed adjustment ratio is used as a fixed ratio to fine-tune the exposure value ratio for each frame so as to control each frame to have a same error, and the instant exposure value ratio of a first row of one of the frames is used as the processor exposure value ratio to be inputted to the image signal processor; and
using the exposure value ratio for each frame of the sequential frames to perform exposure compensation for generating sequential frames undergone a high dynamic range compensation process so as to output an HDR video.

### Claim 9 (depends on 8)

The circuitry according to claim 8, wherein the instant exposure value ratio equals to a previous row exposure value ratio plus an adjustment value for each of the rows.

### Claim 10 (depends on 8)

The circuitry according to claim 8, wherein, in a beginning of the method, a brightness range threshold is set for excluding overly-dark and overly-bright pixels, and a light-dark ratio threshold is set for excluding one or more potential moving regions from the video.

### Claim 11 (depends on 10)

The circuitry according to claim 10, wherein the instant exposure value ratio equals to a previous row exposure value ratio plus an adjustment value for each of the rows.

### Claim 12 (depends on 10)

The circuitry according to claim 10, wherein, when pixel values of two sequential frames are retrieved from the video, a ratio range and an appropriate brightness range are set between the two sequential frames according to the processor exposure value ratio and the brightness range threshold for selecting a valid pixel pair between the two sequential frames within a reasonable ratio after excluding overexposed or overly-dark pixels, and an exposure compensation is performed upon the HDR video with the valid pixel pair between the two sequential frames.

### Claim 13 (depends on 12)

The circuitry according to claim 12, wherein the instant exposure value ratio equals to a previous row exposure value ratio plus an adjustment value for each of the rows.

### Claim 14 (depends on 13)

The circuitry according to claim 13, wherein, when the exposure value ratio for each row of each of the frame is calculated, a threshold for adjusting the exposure value ratio is used to converge the exposure value ratio for each of the frames.

### Claim 15 (depends on 14)

The circuitry according to claim 14, wherein, starting from the processor exposure value ratio initially, the adjustment value of each of the rows and the fixed adjustment ratio are used to converge the exposure value ratio, a removable region with a height in each of the frames is removed after the convergence, and an output image region with another height is taken for outputting the HDR video via an output circuit.