A basic understanding of ccir656

656 the output is serial data, and the synchronous signal of the line field is embedded in the data stream;
601 is parallel data, and the row-field synchronization has a separate output;
656 is only a data transmission interface. It can be said that it is used as a transmission method of 601.
Simply put, ITU-R bt.601 is "Studio digital TV encoding Parameters" standard, while ITU-R bt.656 is the digital interface standard in ITU-R bt.601 Attachment A, used for main digital video equipment (including chips) A digital transmission interface standard that uses a 27 MHz/S parallel port or a 243 Mbit/s serial interface.
The formulation of ccir601 proposal is the first step towards the unification and standardization of digital television broadcasting system parameters. In this suggestion, the basic parameter values of the digital encoding of the TV Center studio of the 625 and 525 lines system are specified.
The coding standard of the TV studio is specified separately in the Recommendation No. 601. It specifies the encoding method, sampling frequency, and sampling structure of color TV signals.
It specifies that the color TV signal uses component encoding. The so-called component encoding means that a color TV signal is first separated into a brightness signal and a chromatic aberration signal before being converted into a digital form, and then encoded separately. The component signal (Y, B -- y, r -- Y) is encoded separately, and then the digital signal is synthesized. It specifies the sampling frequency and structure. For example, in the encoding, the sampling frequency of the specified Brightness Signal and chromatic aberration signal is 13.5mhz and 6.75 MHz, respectively, and the sampling structure is orthogonal, that is, the sampling structure is repeated by line, field, and frame, r-Y and B-Y sampling per line with odd times (1, 3, 5 ......) Y sampling is at the same position, that is, the sampling structure is fixed, and the relative position of the sampling point on the TV screen remains unchanged.
It specifies the encoding method. Linear PCM encoding is performed on the Brightness Signal and two chromatic aberration signals. 8 bits are used to quantify each sampling point. At the same time, it is stipulated that the entire dynamic range of A/D conversion is not used during digital encoding, and only 220 quantization levels are allocated to the brightness signal. The black level corresponds to the quantization level 16, the white level corresponds to the quantitative level of 235. Assign 224 quantization levels for each chromatic aberration signal. The zero level of the chromatic aberration signal corresponds to a quantization level of 128.
To sum up, we know that the encoding data stream of the component signal is very high. Taking the encoding standard as an example, the bit stream is 13.5 × 8 + 6.75 × 8 × 2 = 216 Mb/s. If the 4: 4 encoding method is used, that is, the compound signal is directly encoded, and the sampling frequency is 13.3 × 8 = 106.4 Mb/s.
Differences between the two signals:
ITU-R BT 601 (formerly known as ccir601): 16-bit data transmission; 21-core; y, U, V signal simultaneous transmission.
ITU-R BT 656 (ccir656 old name): 9-core, do not need synchronous signal; 8-bit data transmission; Serial video transmission; transmission rate is 2 times of 601; first pass y, then pass UV.

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The line and field synchronization information of ccir601 must be transmitted through the line and field synchronization signal lines;
Ccir656 does not need these two signal lines. It only uses eight-bit data lines for "soft" synchronization.

Ccir656 = ccir601 + hsync + vsync

ITU-R BT 601:

16-bit data transmission; 21-core; y, U, V signal transmission at the same time.

ITU-R BT 656:

9-core, no synchronous signal; 8-bit data transmission; Serial video transmission; transmission rate is twice the rate of 601; first transfer y, then pass UV.

CCIR 601 suggestions

To facilitate international program exchange, to eliminate standard differences between digital devices and to ensure compatibility between 625-line television systems and 525-line television systems, the international radio Advisory Board (CCIR) in February 1982) 15th plenary meeting, through the 601 suggestions, determine the component encoding based, that is, the brightness component y, and two chromatic components r-y, B-Y as the basis for encoding, as an international standard for digital coding of TV studios.

The standard provisions: (1), whether it is paled, or ntsc TV, Y, r-y, B-Y three-point sampling frequency were 13.5 MHz, 6.75 MHz, 6.75 MHz. (2) linear quantization is used after sampling. The quantified bits of each sample point are used for 10 bits in the studio and 8 bits for transmission. (3). Y, r-y, B-Y three points between the ratio of 4: 2: 2.

At the interim meeting of the International Radio Advisory Board (CCIR), September 1983, three additional provisions were made: (l) specifying that the encoded signal is a pre-calibrated y, (R-Y), B-Y) signal; (2) corresponding to the quantum level 0 and 255 codewords for synchronization, L to 254 of the quantitative level for video signal; (3) the correspondence between the simulation and the number row is further clarified, and the interval from the end of the Number Valid row to the reference time sample is defined, for the standard of 525 rows and 60 fields/second, there are 1 6 samples, and for the standard of 625 rows and 50 fields/second, there are 12 samples. No matter 625 rows/50 rows or 525 rows/60 rows, the brightness sample points of the valid numeric rows are
720, the sample points of the chromatic aberration signal are all 360, which is to facilitate the standard conversion. If the number of brightness samples is divided by two, the data of the chromatic aberration signal is obtained.

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CCIR-656 encoderfrom Adaptive micro-ware, Inc.Features

• Delivers high-quality real-time video encoding
• Complies with ccir656 (bt.656) Standard
• Supports 27-mhz, 8-bit parallel data stream
• Combines input video data, calculated reference codes, and generated blanking data
• Provides external timing reference
• Generates NTSC output
• Uses fully synchronous design

Block digoal

Figure 1 shows a block divisor of the function.

Figure 1. CCIR-656 encoder Function

Description

The CCIR-656 decoder provides real-time digital video processing that is used provided tively for devices and applications including set-top boxes, digital recorders, video conferencing, streaming video, and video security systems.

The CCIR-656 decoder design can synchronize to the incoming ccir656 video data stream and generate the timing signals necessary for other blocks to extract the active video field data. it generates output signals that identify the active video data type
(Luma, chroma red, and chroma blue) available at data_out. the decoder also identifies the Active Portions of the video data stream, the current field outputted, and the video format (NTSC or pal ).