Bt.656 video standards

ITU-R601/656, formerly known as ccir601/656, is a video standard proposed by the International Telecommunications Association.

Glossary: bt.656: This ITU Recommendation defines a parallel interface (8-bit or 10-bit, 27 MHz) and a serial interface (270 Mbps) for the transmission of bt.601 YCbCr digital video between pro-video equipment.

Proposal No. 656-3 of the Radio Communication Department of the International Telecommunication Union:
Working on ITU-RBT.601 recommendations (Part A) of and 525 rows on Level 2
Digital Component Video signal interface in TV System

ITU Radio Communication plenary session considers:
A) for television broadcasting agencies and program producers, it is advantageous to have the same number of important parameters as the maximum number of digital studio standards in the 525 and 625 system;
B) A World-compatible digital method will make the development of devices have many common features, make the operation more economical, and facilitate the exchange of international programs;
C) in order to achieve the above objectives, an agreement has been reached on the basic encoding parameters of the digital TV studio in the form of ITU-RBT.601 recommendations; d) the actual implementation requirements of ITU-RBT.601 Recommendations specify the details of the interface and the data flow through the interface; e) These interfaces should have the largest commonalities in both the 525 and 625 rows; f) in the actual implementation of the ITU-RBT.601 recommendations, we hope to make provisions on the serial and parallel interfaces;
G) the digital TV signals produced by these interfaces may be potential sources of interference to other services, and the radio Rule No. 964 must be given due attention. It is recommended that where the component encoding digital video signal interfaces are required in the TV studio, these interfaces and the data streams through them should comply with the following instructions for the implementation of bit parallel and bit serial:
1 Introduction
This Recommendation describes the interconnection methods for digital television devices that run in line 525 or line 625 and comply with the-2 encoding parameters set forth in ITU-RBT.601 recommendations (Part.
Part 1: Common signal formats of interfaces
1. General Interface Description
Interfaces provide unidirectional interconnection between a single signal source and a single end point. The common single signal formats for parallel and serial interfaces are described in section 2nd. The data signal is encoded into binary information of 8 bits (or 10 bits. These signals are:
1: video signal,
2: scheduled benchmark signal,
3: auxiliary signal.
2. Video data
Table 1 field interval Definition

Note 1: Signals F and V change the status at the beginning of the Digital Line in sync with the scheduled reference code of the valid video.
NOTE 2: For the definition of the number of rows, see the ITU-RBT.470 recommendations. Note that the row number of the numeric row is shown in the ITU-R BT. 601 we recommend that you change the status before 011 as described in (Part.
2.1 encoding features
The video data conforms to the recommended ITU-R bt.601 (Part A) and field blanking definitions shown in table L.
2.2 video data format
The eight most effective bits are all l or 0 data words used to identify the target, so only 256 of the 254 8 bits (1024 of the 1016 10 bits) it can be used to represent the signal value. Video data is transmitted at a rate of 27 megabits/second in the order of CB, Y, Cr, Y, CB, Y, Cr ,...... Among them, CB, Y, Cr refers to the same site brightness and color difference signal sampling, followed by Y corresponds to the next brightness sampling.
2.3 interface signal structure
Figure L shows how the video sampling data is added to the interface data stream. Sample identifiers in Figure L conform to the identifiers recommended for ITU-RBT.601 (Part.
2.4 video scheduled benchmark code (SAV, EAV)
There are two scheduled benchmark signals, one at the beginning of each video data block (start of activevideo, Sav), and the other at the end of each video data block (end of active video, EAV ), l.

Each scheduled baseline signal consists of a sequence of four characters in the following format:
Ff 00 00 XY (the value is in hexadecimal notation, and ff 00 is reserved for the scheduled reference signal .) The first three are fixed prefixes, and the first 4th words contain information that defines the Second Field identifier, the field invisibility status, and the row blanking status.
The bit allocation in the scheduled benchmark signal is listed in Table 2.
Data bits (FF) Second (00) Third (00) Fourth (xy)

NOTE 1: The displayed value is the recommended value for the 10-bit interface.
NOTE 2: to be compatible with existing 8-bit interfaces, the values of D1 and do bits are defined at the end. F = 0/1 l/2, V = 0/1 other places/field invisibility. H = 0/1 effective video start (SAV)/Effective video end (EAV) P0, P1, P2, P3: Protection bits (see table 3) MSB: the highest valid bits table L specifies the states of the V and F bits. The statuses of P0, P1, P2, and P3 bits depend on the statuses of F and V bits. See table 3. In the receiver, this arrangement allows correction of L-bit codes and detection of 2-bit codes.

2.5 Auxiliary Data
The auxiliary data synchronized to the multiplexing group at a rate of 27 mword/s during the invisibility period is specified. Secondary data signals can be transmitted in the form of 10 bits only during the Line Blanking period, and can also be transmitted in the form of 8 bits only when the line in the field is valid (it should be noted that: A digital video recorder that complies with the recommendations of the ITU-RBT.657 does not record data during the invisibility period, nor does it record certain rows during the invisibility period ). The data values 00.xh and ff. Xb (see section 2.2) are retained for the purpose of identification. Therefore, it cannot appear in secondary data.
The prefix ff. x ff. X must be added to all auxiliary data signals contained in the valid part of the row during off-site hiding. Unless used as a special device, the auxiliary signal should not be changed by the device.
2.6 Data words during the invisibility Period
When data words that do not require regular reference codes or auxiliary data appear during the digital invisibility period, you should fill in the appropriate positions in the reused data, which is equivalent to CB, Y, Cr, Y Signal hiding level of 80.0 H, 10.0 H, 80.0 H, 10.0 H and other sequences. Horizontal format

The overall format of one complete line of the digital video data stream provided des The following sections. The horizontal scan is considered to start with the beginning of the EAV section.

· EAV-end of active video (timing reference signal) 2 samples (4 words)
· Horizontal blanking 134 samples (268 words)
· Sav-start of active video (timing reference signal) 2 samples (4 words)
· Active video 720 samples (1440 words)

EAV timing reference signal:

The EAV timing reference consists of four words in the following format:

Where:
F = field select (defines which vertical scan during interlace scanning)
V = vertical blanking
H = 1 indicating EAV
E3 = V XOR H
E2 = f XOR H
E1 = f XOR v
E0 = f XOR v XOR H
Horizontal blanking:
The horizontal blanking section consists of a repeating pattern: 1000 0000 0001 0000 ........
Sav timing reference signal:

The SAV timing reference consists of four words in the following format:

Where:
F = field select (defines which vertical scan during interlace scanning)
V = vertical blanking
H = 0 indicating Sav
E3 = V XOR H
E2 = f XOR H
E1 = f XOR v
E0 = f XOR v XOR H
Active video:

The active Video Section consists of the Y, CB, Cr data in the following sequence. The y, CB and Cr values are the scaled, offset, digitized versions of Y, U and V.

· Cr
· Y
· CB
· Y

Vertical format
The details of the vertical format are shown in the complete screen diagrammed below. the scan is of the interlace type which means that the odd lines are scanned first, followed by the even lines. the symbols "F" and "V" refer to the values contained in BITs P8 and P7 of the EAV and Sav timing reference words.