With the popularity of large-screen HD LCD TVs and plasma displays, digital TV broadcasting and high-definition signal interfaces are also becoming increasingly popular. However, it is still necessary to be able to support traditional sources with the highest quality. The 3D comb video decoder is a key processing module that has a significant impact on the overall performance of the system. This article refers to the address: http:// In the initial development phase, the TV only supported playback and display of monochrome (ie black and white) images. With the development of technology, color TV broadcasting is also supported, but it is still necessary to maintain backward compatibility of black and white television display devices. The TV needs to contain color information in the available bandwidth range and continue to display undistorted black and white images in a format like the early TV. The 3D comb video decoding solution delivers outstanding video quality. This method can fundamentally eliminate bad image artifacts such as point creep, "hanging point" and cross color. Wire harness refers to a product assembled by wires and connectors. There are many brands of connectors, including terminals, plastic shells, and plugs.
Wire harness is one of the fastest-growing, most market-demanding and most convenient products in today's electronic and information age industries. Wire harnesses are widely used in military equipment and other equipment. At present, the wire harnesses we have come into contact with are made of various wires and cables according to different circuit numbers, hole numbers, position numbers and electrical principle requirements. The assembly of the wire harness composed of the components, the external protection and the connection of the nearby system, but the product application of the wire harness is mainly in the functions of four parts. According to the application scenario, various functional cables will be selected for matching applications. Screen drive wire harness, control wire harness, power control, data transmission, etc., the classification of product categories will be more, roughly including railway locomotive wire harness, automobile wire harness, wind power connection wiring harness, medical wire harness, communication wire harness, household wiring harness, industrial control Cable Assembly, etc. ;The wiring harness is a variety of complete equipment, instrumentation, and basic equipment that is indispensable for signal and power transmission. It is a necessary basic product in the future electrification and information society. The following are common wiring harness products. You have seen several ?
1. The screen driving wiring harness is mainly used in the driving lines of various display screens, as long as it is used in the field of display screens;
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In a composite video signal, the color information shares the same bandwidth as the available luminance information. Sine waves of different amplitudes and phases represent the chrominance content of any transmitted image (Figure 1). Therefore, the chromaticity must be separated from the brightness to display the picture correctly. 
Figure 1: Luminance information and chrominance information share the same spectrum of a composite video signal.
The chrominance information is placed at the high end of the spectrum and is a multiple of the line length. The difficulty in display is how to properly extract luminance information and chrominance information, and how to maintain full bandwidth without causing display artifacts.
If the luminance-chrominance separation does not occur, the color information makes the picture brighter or darker when the carrier is cycled or reversed. At the same time, the color information will also appear incorrectly in the black and white part of the image (Figure 2). 
Figure 2: Images without luminance and chrominance separation contain a large number of artifacts.
Separating the luminance and chrominance with a simple notch filter or bandpass filter results in a chrominance residual in the luminance signal path and a residual luminance in the chrominance signal path (Figure 3). Residual information can cause serious image artifacts such as “spot creep†(Figure 4). The residual chrominance information in the chrominance path also causes artifacts such as "cross-color" (Figure 5).
Figure 3: Separation of luminance and chrominance using a notch filter or bandpass filter. 
Figure 4: The TV misinterprets the residual color in the luminance path as luminance information, resulting in a bad point creep effect. 
Figure 5: The residual luminance signal in the chrominance path causes cross-color artifacts.
The signal delay function of the comb filter itself causes constructive and destructive interference. The frequency response of the comb filter consists of a series of evenly spaced spikes in the shape of a comb. Compared to notch filters and bandpass filters, 2D comb filters provide higher video decoder performance (Figure 6). 
Figure 6: The three-line 2D comb filter will use input-output one-line delay.
The 2D comb filter works by: if there are several lines above and below the target line of the image, the chromaticity and brightness can be more completely separated.
In the NTSC (National Television System Committee) format, the chrominance sine wave signal changes 180° line by line. Any two consecutive lines are added, the luminance content is doubled, and the chrominance content is cancelled. Conversely, if two lines are subtracted, the luminance content is cancelled and the chrominance content is doubled. For example, for a full-screen color bar, each active row is visually identical. At a given signal level, the luminance content of each line is the same. In addition to the phase change, the chroma content of each line is the same.
Video decoders (such as Analog Devices' decoders) use a five-line 2D comb filter to provide better performance for NTSC and PAL (Phase Alternating Line) sources. Depending on the complexity of the image, the comb processor must determine if the current line is to be combined with the next or previous line.
The comb processor cannot combine arbitrary lines for certain images, and the current line can be cut at this time. An adaptive 2D comb video decoder can provide an acceptable level of performance. However, when the continuous lines are different, the 2D comb filter does not work properly and turns to the notch filter to separate the luminance and chrominance of the line region.
Although it is important to successfully achieve luminance and chrominance separation without image artifacts or bandwidth limitations (which translates into low-contrast images), many other aspects of video signals, such as poor time bases or non-standard weak RFs. Signals also bring a lot of challenges.
Artifact or image defects acceptable for small CRT displays are unacceptable for next-generation plasma displays and LCD displays. Because of the increased resolution, size, and display contrast, even small image defects can be noticeable.
Adaptive 3D comb filter technology
High-definition (HD) sources, digital interfaces, and high-resolution displays deliver a great visual experience. However, through channel switching or input, users may see beautiful high-definition images, or traditional composite video broadcasting (CVBS). The quality of standard-definition (SD) composite video images has been significantly improved with high-quality adaptive 3D comb filter technology (Figure 7). 
Figure 7: Typical architecture of a decoder with a built-in 3D comb filter.
The 3D comb filter is similar to a 2D comb filter that separates luminance and chrominance by combining pixel combinations of certain lines. The main difference between the two is that the 2D comb filter combines the pixels of successive lines of the image, while the 3D comb filter combines the pixels of the current line with the pixels in the same row of the image delay state (Figure 8).
Figure 8: The result of the decoder of the adaptive built-in 3D comb filter (a) is significantly better than the decoder (b) with the built-in 2D comb filter.
In addition, thanks to the luminance and chrominance separation of 3D comb video decoding, the method maintains the full bandwidth of the luminance and chrominance data packets.
The full-brightness bandwidth preserves high-frequency content and provides crisp, clear images that allow users to distinguish tiny details. Full color bandwidth ensures brighter, clearer colors.
2D comb video decoding mainly processes adjacent active video lines, analyzes them, or both processes and analyzes them, while 3D comb processing compares frame-to-frame video pixel information (Figure 9). It compares the data of the current frame with the previous frame of data in the memory. 
Figure 9: A typical frame sequence of the NTSC system shows a 3D comb filtering technique.
If two frames are added at the same time, the chrominance information of each pixel is cancelled, and the luminance pixel data is doubled. Similarly, if the previous frame is subtracted from the current frame, the luminance pixel data is cancelled and the chrominance information is doubled.
Despite the many advantages of 3D comb filtering, designers must address their performance limitations and challenges. The 3D comb filter perfectly separates the brightness and chromaticity of the image, which is not the case with traditional 2D comb filters or notch filters.
However, the perfect separation of brightness and chrominance is achieved only when the pixels in the image are absolutely still. Conversely, if the image is moving and the pixel data of two consecutive frames is changing, the 3D comb filter cannot be used (Figure 10). Importantly, the video decoder examines each pixel and compares it with previously stored pixel data to determine if a shift has occurred to determine which comb filter should be used. 
Figure 10: Comb filtering of moving images produces significant artifacts.
Due to the complexity of motion detection, the method used must be able to analyze each active pixel of the current and stored frames to determine which method to use to separate the information.
The 3D comb filter technique combs the still pixels, the 2D comb filter technique processes the areas without complex motion, and the notch filter performs the processing of complex motion regions. The main challenge of the 3D comb decoder is not the 3D combing process itself, but the complex motion detection and adaptive switching between the 3D comb filter, the 2D comb filter and the notch filter.
When the comb filter is not competent
The adaptive 3D comb filter relies on a decoder to correctly detect image movement. Otherwise, the comb filter will not process the pixel data correctly, causing motion artifacts (Figure 11). The bird's wings are downward in Figure 11a. The wings in Figure 11b have been dancing upwards, while the wings in Figure 11c are again down. This is the normal order in which the birds dance their wings. 
Figure 11: The adaptive 3D comb filter relies on a decoder to correctly detect image movement. This is the normal sequence of birds dancing wings - down (a), up (b), then down (c).
Many 3D comb decoders check Frame 1 and Frame 3, and find that Frame 1 and Frame 3 are identical, and it is mistaken that no image shift has occurred. It was therefore decided to process the data with a 3D comb decoder (Fig. 12). 
Figure 12: Using a 3D comb decoder, invalid detection causes significant mesh artifacts (a). After image motion correction, meshless artifact generation (b).
In contrast, high performance video decoders with 3D comb filters utilize many frame memories to more accurately detect motion between all frames. It is necessary to use a large number of frames to help the decoder accurately determine when and where to use the 3D comb filter.
Achieve more features
The 3D comb filter needs to work normally, and the memory buffer needs to store video pixel data frames for analysis and processing. A decoder such as the ADV7802 12-bit SD/HDTV video decoder from Analog Devices, Inc., equipped with a 3D comb filter and a graphic digitizer to handle other non-3D comb filter tasks such as advanced timing noise reduction, max. Use memory space to the limit.
With a 3D comb filter, the ADV7802 uses a variety of techniques to compare the pixel data of the current frame with previously stored data to filter and eliminate image noise.
Advanced memory can also implement advanced time base correction. Frame-based time-base correction ensures that the decoder always outputs a fixed clock, a fixed number of samples per line, a constant number of lines per frame, and the correct field order.
While television applications typically do not require external memory, more and more manufacturers are moving more receivers and electronic control devices into separate remote control boxes to minimize the thickness of the display panel. However, this type of design also limits the number of cables that need to be directly connected to the TV set, which can cause wiring difficulties (Figure 13). 
Figure 13: The thin display panel transfers the receiver and electronic control unit to a separate unit.
The remote control box is connected to the display via HDMI (High Definition Multimedia Interface) or similar link. When the link works, the TV needs stable pixel and clock data. Since the time base correction allows the video decoder and the link's transmitting device to be directly connected, the decoder can even provide reliable timing and pixel data for non-standard input devices.
In addition to luminance and chrominance separation, many other aspects of composite video processing directly affect picture quality. The performance of the ADC input plays a decisive role in the overall video quality received by the display.
Professional quality video decoders such as the ADV7802 utilize a 12-bit ADC to achieve a signal-to-noise ratio better than 62dB. It is worth noting that for performance-oriented applications, the differential phase shift and gain can exceed 0.45 ° and 0.45%, respectively. For cost-sensitive applications, a video decoder with a 9-bit ADC can be used, such as the Analog Devices ADV7180.
The decoder must also be able to handle non-standard and weak broadcast sources. TV users and manufacturers still attach great importance to these requirements. Consumers who have just purchased a new high-end large-screen plasma or LCD TV may also connect it to a 12-year-old VCR and analog RF cable system.
In the past, consumers connected video recorders to old CRT TVs, and now they expect HDTVs to deliver at least as good performance levels as older CRT TVs. In other words, the video of the recorder should be stable, even if it is in “trick†mode (ie, pause, fast forward, or rewind).
The weak RF signal should also be synchronized with the color lock, even if the input signal drops below 25dBμV. To address the problems associated with low-level RF and video signals and older non-standard systems, decoder designers face many challenges.
When deciding the quality level reference for the decoder, which algorithm to use requires careful consideration. Many manufacturers are selling their own to successfully handle these sources. For example, Analog Devices' video decoder integrates technologies such as synchronous detection and extraction, resampling, and advanced back-end FIFO management.
Intelligent filtering algorithms such as the ADV7802 use phase-locked loop (PLL) blocks, as well as horizontal sync (HSYNC) and vertical sync (VSYNC) processor blocks to ensure proper synchronization of information. This filter ensures that the decoder is able to recognize the period in which it looks for synchronization information. The genlock circuit module and the processor module ensure that the detected synchronization information is correctly aligned.
2. Control wire harnesses are mainly used to connect circuit boards to control electrical signals, financial equipment, security equipment, new energy vehicles and medical equipment;
3. Power control lines, such as switching power lines, computer power lines, etc;
4. Data transmission line, upload and download signals, such as HDMI, USB and other series.
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