Multimedia Hardware

ISP Introduction

Introduction

ISP stands for Image Signal Processor. It is a hardware block on a camera chip that is responsible for processing the raw image data captured by the camera sensor. The ISP performs a variety of tasks on the image data, including:

  • Color Correction

The ISP corrects for the color bias of the camera sensor. This is necessary because the color response of the sensor can vary depending on the lighting conditions.

  • White Balance

The ISP sets the white balance of the image. This is necessary to ensure that the colors in the image are accurate.

  • Noise Reduction

The ISP reduces the noise in the image. This is necessary to improve the image quality.

  • Sharpening

The ISP sharpens the image. This is necessary to make the image look more crisp.

  • Gamma Correction

The ISP adjusts the gamma curve of the image. This is necessary to ensure that the brightness levels of the image are correct.

  • Dynamic Range Compression

The ISP compresses the dynamic range of the image. This is necessary to ensure that the image does not have too much contrast.

  • Color Space Conversion

The ISP converts the image from the camera sensor’s native color space to the color space that the device is using. This is necessary so that the image can be displayed correctly on the device’s screen.

The ISP is a complex and powerful hardware block that is essential for capturing high-quality images.

The ISP is made up of several internal modules, including:

  • Color Correction Module

The Color Correction Module corrects for the color bias of the camera sensor. This is necessary because the color response of the sensor can vary depending on the lighting conditions.

  • White Balance Module

The White Balance Module sets the white balance of the image. This is necessary to ensure that the colors in the image are accurate.

  • Noise Reduction Module

The Noise Reduction Module reduces the noise in the image. This is necessary to improve the image quality.

  • Sharpening Module

The Sharpening Module sharpens the image. This is necessary to make the image look more crisp.

  • Gamma Correction Module

The Gamma Correction Module adjusts the gamma curve of the image. This is necessary to ensure that the brightness levels of the image are correct.

  • Dynamic Range Compression Module

The Dynamic Range Compression Module compresses the dynamic range of the image. This is necessary to ensure that the image does not have too much contrast.

  • Color Space Conversion Module

The Color Space Conversion Module converts the image from the camera sensor’s native color space to the color space that the device is using. This is necessary so that the image can be displayed correctly on the device’s screen.

The ISP modules work together to process the raw image data from the camera sensor and produce a high-quality image that can be displayed on the device’s screen.

Work with Camera Sensor and SOC

An Image Signal Processor (ISP) is a hardware block on a camera chip that is responsible for processing the raw image data captured by the camera sensor. The ISP works with the camera sensor and the System on a Chip (SoC) to produce a high-quality image.

The camera sensor captures the raw image data. The ISP then processes this data to correct for the color bias of the sensor, set the white balance, reduce noise, sharpen the image, adjust the gamma curve, compress the dynamic range, and convert the image from the sensor’s native color space to the color space that the device is using.

The ISP then sends the processed image data to the SoC. The SoC then displays the image on the device’s screen.

Here is a more detailed explanation of how the ISP works with the camera sensor and the SoC:

  1. The camera sensor captures the raw image data. The raw image data is a 2D array of pixel values. Each pixel value represents the brightness of a single pixel in the image.
  2. The ISP then processes the raw image data. The ISP performs a variety of operations on the image data, including:
    • Color correction: The ISP corrects for the color bias of the camera sensor. This is necessary because the color response of the sensor can vary depending on the lighting conditions.
    • White balance: The ISP sets the white balance of the image. This is necessary to ensure that the colors in the image are accurate.
    • Noise reduction: The ISP reduces the noise in the image. This is necessary to improve the image quality.
    • Sharpening: The ISP sharpens the image. This is necessary to make the image look more crisp.
    • Gamma correction: The ISP adjusts the gamma curve of the image. This is necessary to ensure that the brightness levels of the image are correct.
    • Dynamic range compression: The ISP compresses the dynamic range of the image. This is necessary to ensure that the image does not have too much contrast.
    • Color space conversion: The ISP converts the image from the sensor’s native color space to the color space that the device is using. This is necessary so that the image can be displayed correctly on the device’s screen.
  3. The ISP then sends the processed image data to the SoC. The SoC then displays the image on the device’s screen.

MIPI

The MIPI CSI (Camera Serial Interface) bus has four layers:

  1. Physical layer: The physical layer is responsible for transferring the data between the camera sensor and the ISP. The physical layer uses a high-speed serial interface to transmit the data.
  2. Link layer: The link layer is responsible for error correction and flow control. The link layer ensures that the data is received correctly and that the data is not lost.
  3. Data Link layer: The Data Link layer is responsible for transferring the data between the camera sensor and the ISP. The Data Link layer divides the data into frames and sends the frames over the MIPI bus.
  4. Application layer: The application layer is responsible for handling the data after it has been received by the ISP. The application layer decodes the data and provides it to the application that is using the camera.

The camera sensor sends the data to the ISP over the MIPI CSI bus. The physical layer of the MIPI CSI bus transfers the data between the camera sensor and the ISP. The link layer of the MIPI CSI bus ensures that the data is received correctly and that the data is not lost. The Data Link layer of the MIPI CSI bus divides the data into frames and sends the frames over the MIPI bus. The application layer of the MIPI CSI bus decodes the data and provides it to the application that is using the camera.