ISP DSP diff

Source: Internet
Author: User
Tags diff

The ISP is the abbreviation for Image Signal Processor, which is the graphics signal processor. DSP is the abbreviation of digital Signal Processor, also known as the signal processor.

The ISP typically handles output data from image sensors, such as AEC (AE control), AGC (Automatic gain control), AWB (auto white balance), color correction, Lens shading, Gamma correction, removal of bad points, Processing of auto Black level, auto white level and so on.

And the DSP function is more, it can do some photography and echo (JPEG codec), video and playback (video codec), the codec , and many other aspects of processing, In short, the digital signal is processed. Personally, the ISP is a special kind of DSP for processing image signals.
image sensor
Image sensor is an important part of digital video camera. According to the different components, can be divided into CCD and CMOS two major categories. such as Sony's ICX 445, ICX274, Imx035/036,aptina mt9m033, mt9d131, Mt9t031,omnivison of OV2715 and so on. The role of image sensors is to capture and convert optical images into the electrical signals available to back-end ISPs.

In the past, we used to say that CCD is a high-end technology component used in image products, and CMOS is used in low image quality products due to its low-light performance, exposure mode and other technical performance. Today, the rapid development of CMOS technology, such as Sony introduced the use of Exmor technology imx035/036 image sensor, its low-light performance, image resolution and frame rate, chip processing speed has a large degree of performance improvement. ISP image signal processing device

ISP (Image Signal Processor) Image signal Processor is the main function of the front-end image sensor output signal to do a later processing. Different ISPs are used to match image sensors from different vendors. ISP's excellence in the entire camera product is very important, it should be said that it directly affects the quality of the image presented to the user. After the image has been acquired by CCD or CMOS, it needs to be processed in a later stage to adapt to different environments and to restore the site details in different optical conditions. In the ISP it will complete the 2A (awb/ae, auto white balance/ae) or 3A (AWB/AE/AF, auto white balance/AE/auto-focus) we often mention. In traditional mode, a DSP or an FPGA is used to finish the post-processing of the image. Some camera products support the 3D noise reduction function, wide dynamic, slow shutter, frame accumulation, strong light suppression and other functions are also done by the ISP.

ISPs currently used in HD camera products typically have the following sources:

Manufacturer's own research and development: HD camera Equipment manufacturers in order to better match the back-end compression, function development, self-developed ISP processing algorithm, the algorithm is integrated into the FPGA or DSP chip, connected to the front-end image sensor.

Third-party research and Development: in 2010, a number of ISP solutions launched by non-HD camera manufacturers were introduced, and they sold different ISP chips directly to camera manufacturers to match the sensor of different manufacturers.

Set mode: By the sensor manufacturers will be developed by the ISP with home sensor to form an image acquisition processing solution to customers, wherein the image processing algorithm and a variety of debugging work has been completed, the camera manufacturers only need to do interface docking and back-end compression or conversion into digital video (HD-SDI) can be. This pattern we call stand-alone devices or camera System onchip. compression processor or digital video conversion

Let's begin by understanding the concepts of compression processing and digital video conversion. After the ISP has processed the front-end image sensor signal, it is generally transmitted to the back-end processing chip in digital interface format such as MPTE296M/BT.1120/YUV 4:2:2. The compression processor (SOC or DSP) can encode the video signal in the H.264/MPEG-4/MJPEG algorithm and then transmit it to the user via the built-in network service with the TCP/IP protocol network signal. Digital video Conversion is a non-compression method, digital video converter chip to the ISP output digital signal conversion to SD-SDI/HD-SDI/3G-SDI signal, respectively, corresponding to standard definition (VGA), high-definition standard (1080P@30FPS), 1080p@60fps even higher resolution. HD-SDI HD video signals require dedicated transmission peripherals such as SDI optical end machines, SDI matrices, and more.

Low illumination refers to the brightness value of the scene when the brightness of the subject is low to a certain extent, so that the video signal level of the camera output is low to a certain specified value. When determining this parameter, the maximum relative aperture of the lens should also be specified.
For example, using the lens of F1.2, when the brightness value of the scene is as low as 0.04LX, the camera output video signal amplitude of the maximum value of 50%, that is, to reach 350mV (the standard video signal maximum amplitude 700mV), the
camera is said to have a minimum illumination of 0.04lx/ F1. 2. The brightness value of the photographed scene is lower, the video signal output to the amplitude of less than 350mV, reflected in the monitor screen,
will be a screen difficult to distinguish the level of gray images.

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