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GY/T 187-2002 English PDF

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GY/T 187-2002: Serial multichannel audio digital interfance
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GY/T 187-2002	English	359	Add to Cart	3 days [Need to translate]	Serial multichannel audio digital interfance	Valid	GY/T 187-2002

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Basic data

Standard ID	GY/T 187-2002 (GY/T187-2002)
Description (Translated English)	Serial multichannel audio digital interfance
Sector / Industry	Radio, Film & TV Industry Standard (Recommended)
Classification of Chinese Standard	M64
Classification of International Standard	33.160
Word Count Estimation	11,110
Date of Issue	2002-12-20
Date of Implementation	2003-02-01
Adopted Standard	AES 10-1991, IDT
Summary	This standard specifies the multi-channel audio digital serial interface (MADI) data structure and electrical characteristics. This standard applies to coaxial cable or fiber optic cable on a linear representation of the sampling frequency range of 32kHz ~ 48kHz (�� 12. 5%), a resolution of 24 bits per channel, 56 -channel digital audio serial transmission. This standard is only supported from a transmitter to a receiver point-to- point connection.

GY/T 187-2002: Serial multichannel audio digital interfance

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Serial multichannel audio digital interfance People's Republic of China Radio, Film and Television Industry Standard GY Multi-channel audio digital serial interface Serial multichannel audio digital interface (AES10-1991 (ANSI S4.43-1991), IDT) 2002-12-20 released 2003-02-01 Implementation Published by the State Administration of Radio, Film and Television

Foreword ... II 1 Scope ... 1 2 Normative references ... 1 3 Terms and definitions ... 1 4 Format ... 1 5 Sampling frequency and bit rate ... 5 6 Synchronization ... 5 7 Electrical characteristics ... 6 Appendix A (informative) Example of link coding ... 8

Foreword

This standard is equivalent to AES10-1991 (ANSI S4.43-1991) "Multi-channel Audio Digital Serial Interface", English name. Serial multichannel audio digital interface (MADI). This standard was developed for the design, production, acceptance, operation, maintenance, and use of multi-channel audio digital serial interfaces and related equipment systems. Use, especially multi-channel digital audio program production and exchange, and then improve the broadcast quality and level, providing a technical basis. Appendix A to this standard is an informative appendix. This standard is under the jurisdiction of the National Radio and Television Standardization Technical Committee. This standard was drafted. Central People's Broadcasting Station. The main drafters of this standard. Lin Qiangjun, Guan Yi, and Sun Haihong. Multi-channel audio digital serial interface

1 Scope

This standard specifies the data composition and electrical characteristics of the multi-channel audio digital serial interface (MADI). This standard applies to linear or coaxial cable or fiber optic cable. The sampling frequency ranges from 32kHz to 48kHz (± 12.5%). 56-channel digital audio serial transmission with a resolution of 24 bits per channel (see Figure 1). This standard only supports point-to-point connections from a transmitter to a receiver.

2 Normative references

The clauses in the following documents have become the clauses of this standard after being referenced. For dated references, all subsequent Neither amendments (excluding errata) or revised versions are applicable to this standard, however, parties who have reached an agreement under this standard are encouraged to study Is the latest version of these files available? For undated references, the latest version applies to this standard. GY/T 158-2000 studio digital audio signal interface

3 terms and definitions

The following terms and definitions apply to this standard. 3.1 Audio sample data An audio signal that is periodically sampled, quantized, and digitized in two's complement form. 3.2 Channel A set of audio sample data corresponding to a signal transmitted within any period of the sampling frequency of the data source, which is accompanied by other Data bits. 3.3 Two-channel format GY/T 158-2000 bit, block and sub-frame structure (without preamble). 3.4 Frame Numbered 56-channel sequence from 0 to 55, each frame contains the audio sample data transmitted in any sampling period Processing and related data. Start with the first bit of channel 0 as the frame. 3.5 Link Connection of a single serial multi-channel audio digital transmitter and a single multi-channel audio digital receiver.

4 Format

4.1 Frame Format Each frame contains 56 channels, represented by the numbers 0 to 55. Starting from channel 0, the channels in the frame are arranged continuously. The frame format is shown in Figure 2. Show. 4.2 Channel format Each channel contains 32 bits. 24 of which are allocated to audio or other data defined by audio/non-audio tags, with another 4 This bit is used to indicate the valid bit (V), user data bit (U), status data bit (C), and parity of the GY/T 158-2000 two-channel interface. Check bit (P), the other 4 bits are used for mode confirmation. GY/T 158-2000 two-channel format is reserved here. The channel format is shown in Figure 3. MA DI RZ RX 4.2.1 Mode bits The mode bits are provided for frame synchronization. For example, the block of each two-channel interface in GY/T 158-2000 starts; GY/T 158-2000 two-way interface Discrimination of the A and B subframes in the channel interface; and the active/inactive status of each channel. 4.2.2 Description of audio data In audio mode, the 24-bit audio data is represented in linear two's complement form, and the most significant bit (MSB) is transmitted last. aisle All unused audio bits are set to 0, and the V, U, C, and P bits are set to default values. Their definitions are connected to the GY/T 158-2000 two-channel interface. The format is the same. 4.2.3 Activate the channel All active channels are arranged in order, starting from channel 0. The activation bit shall be set to 1 for each active channel. 4.2.4 Inactive channels All bits, including the active bit, shall be set to 0 on all inactive channels. The channel number of the inactive channel is always the highest The higher channel number should be higher. 4.2.5 Bit description The bit descriptions are shown in Tables 1 and 2. 4.3 Transmission Format 56 channels are serially transmitted through NRZI non-polar code, using 4B/5B encoding format. Table 1 Bit description of channel data Bit name description value 0 MADI channel 0 frame sync bit 1 = true 1 MADI channel activation channel activation bit 1 = true 2 MADI channel A/B GY/T 158-2000 A/B 3 MADI Channel Block Sync Channel Block Start 1 = true 4 ～ 27 GY/T 158-2000 The 27th bit of the data bit should be the most significant bit (MSB) 28 GY/T 158-2000 V significant digits 0 = true 29 GY/T 158-2000 U User data bit 0 = true 30 GY/T 158-2000 C status data bit 0 = true 31 GY/T 158-2000 P Parity (except bits 0 to 3) Even parity Table 2 Bits 2 and 3 (compatible with GY/T 158-2000) Bit 2 and Bit 3 2 channel format description 0 0 Format 2 A channel 0 1 Format 1 A channel block start status 1 0 Format 3 B channel 1 1 Format 4a B channel block start status a Not available for every GY/T 158-2000 Coding diagram For encoding, the 32-bit channel data is divided into 8 words in groups of 4 bits, as shown in Table 3. Each 4-bit (4B) word is encoded into a 5-bit word, see Table 4. Every 5 bit (5B) words are transmitted from the left, see Table 5. The coding scheme allows a low-current DC bias to remain on the link. Although the link signal is not DC, the audio signal can be Can contain DC. Figure 4 shows the link transmission format of a channel. For clarity, Appendix A illustrates the encoding of a single channel word process. Table 3 Word structure Word channel data bits 2 89 .. 3. 4. 5. 6. 7 .. 31 Table 4 4B/5B coding 4-bit data 5-bit coded data Table 5 Arrangement of data transmission within words Word channel connection bit word channel connection bit 4.3.1 Sync Signal A synchronization signal 11000 10001 should be inserted in the data stream at least once per frame to ensure synchronization between the transmitting end and the receiving end. Should be enough The synchronization signal and the encoded data word are interleaved into the frame to meet the requirements of the link. The synchronization signal is transmitted from the left. The synchronization signal can only be inserted at the 40-bit channel boundary, and transmitted between the channels, the idle interval or both at the last channel of each frame After sending, it can be inserted repeatedly. The placement order of the synchronization signals is not specified. Figure 5 shows several possible placement positions of the synchronization signals. Figure 5 Some allowed sync signal positions 4.3.2 Transmission sequence In any bit order, the left symbol on the figure is always transmitted first in time. 4.3.3 Non-Return-to-Zero Inversion Link channel data is transmitted using non-return-to-zero phase-inversion non-polarity coding. Each high-level bit is expressed in steps based on the previous bit. As shown, each low-level bit is represented by no step. Therefore, 1 is represented by a high-low or low-high step of the level, while 0 is represented by a continuous High or persistently low. Note. For examples of non-return-to-zero reversion, see Appendix A.

5 Sampling frequency and bit rate

5.1 Sampling frequency The link operates at a nominal sampling frequency range of 32kHz to 48kHz and can operate within its ± 12.5% frequency range. It can also accommodate higher sampling frequencies (such as 96kHz) when using two or more channels per audio sample on the link. 5.2 Link transmission rate The link transmission rate should be 125Mbit/s, regardless of the sampling frequency or the number of active channels. Note. The error of this 125Mbit/s link transmission rate should be ± 10-4. 5.3 Data transmission rate The data transmission rate should be 100 Mbit/s. The difference between the data transmission rate and the link transmission rate is due to the coding design (see 4.3.1). 5.4 Maximum usage data rate With a sampling frequency of 48kHz × (1 12.5%), the maximum usage data rate of the 56 channels is 96.768 Mbit/s. 5.5 Minimum usage data rate With a sampling frequency of 32kHz × (1-12.5%) for the 56 channels, the minimum usage data rate is specified as 50.176 Mbit/s.

6 Sync

This part includes the synchronization of a master synchronization signal at the receiving end and the transmitting end, which is not only applicable to the master-slave connection. Channel 0 Channel 1 Channel 2 Channel N Channel N 1 Channel N 2 Channel 54 Channel 55 Sync Sync Channel 0 (next frame) Start of frame 6.1 Sync signal The main synchronization signal should be assigned to each receiving end and transmitting end separately. The synchronization signal should be consistent with GY/T 158-2000. 6.2 Sampling timing The sampling timing information is not considered to be carried on the link. The precise timing of connected devices is controlled by a separately assigned master synchronization signal, not by multi-pass Audio digital interface is provided. 6.3 Transmission frame start time The start time of the frame output from the transmitting end should be within ± 5% of a sampling period. The reference time for the number definition is determined. 6.4 Receive frame start time The receiving end should be able to correctly demodulate a signal that changes within ± 25% of a sampling period. The reference time for the step signal definition is determined.

7 Electrical characteristics

The transmission medium shall be a 75Ω coaxial cable (see 7.1) or an optical cable (see 7.2). In order to accurately simulate the normal transmission signal, the test is replaced by a pseudo-random code generator with a sequence length of at least 216-1. The encoder inputs data and accesses it before the 4B/5B bit encoder. 7.1 Coaxial cable 7.1.1 Transmitter 7.1.1.1 Line driver The line driver should have a single-ended output with an output impedance of 75Ω ± 2Ω. Connected actual circuits, such as emitter-coupled logic (Emitter-Coupled Logic) The connection between the signal transmitter and the coaxial cable is shown in Figure 6. Figure 6 MADI Transmitter Line Driver 7.1.1.2 Average output After the line is terminated, the average output voltage relative to the signal ground should be 0 V ± 0.1V. 7.1.1.3 Peak output After the line output terminal is terminated with a 75Ω resistor, its peak-to-peak output voltage should be between 0.3V and 0.6V. 7.1.1.4 Rise and fall times After the line output terminal is terminated with a 75Ω resistor, the rise and fall times measured at the 20% and 80% amplitude points should not be longer than 3ns. At 1ns. The average relative timing difference of the amplitude points should not be greater than ± 0.5ns. 7.1.2 Receiver When the eye diagram measured at the input meets the characteristics shown in Figure 7, the receiver should be able to correctly interpret the received signal. 0V 0V 5V 150n O/P 1 O/P 2 TX 150n IN4148 IN4148 IN4148IN4148 120R 100R 100R 10K 10K 68R 68R 120R tnom = 8ns; tmin = 6ns; Vmax = 0.6v; Vmin = 0.15v. Figure 7 Eye diagram of maximum and minimum input signals 7.1.3 Cable The coaxial cable used should have a characteristic impedance of 75Ω ± 2Ω, and the attenuation in the frequency range of 1MHz to 100MHz should be less than 0.1dB/m. 7.1.4 Connector BNC connectors are used throughout the link. Couplings shall be used for coaxial cable connections. 7.1.5 Cable length The cable length should be less than or equal to 50m. Equalization should not be used. The signal should be no worse than the eye diagram defined in Figure 7. 7.1.6 Example of Interface Circuit The connection between the coaxial cable and the balanced emitter-coupled logic signal can be achieved by a circuit as shown in FIG. 8. 7.1.7 Ground The coaxial cable sheath should be grounded at the transmitting end. In order to minimize RF radiation, it is recommended that the coaxial cable should be directly fixed to the equipment On the box. When the radio frequency is higher than 30MHz, the coaxial cable should be grounded and connected to the receiving end case. This connection is recommended as a coaxial cable connector housing Capacitively coupled to the receiver chassis. A suitable capacitor value is 1000pf. Capacitors should be low inductance, between 30MHz and 500MHz Has a sufficiently low impedance. The wire bonding length should be as short as possible. This prevents possible audio ground currents. Figure 8 MADI buffer amplifier circuit diagram 7.2 Optical cable To be determined. Vmax Vmin tmin tnom 5V 0V 300R 100R 68R 68R 4K7 IN4148 75R 1000PF 10n 1/16V -5V I/P RX (s) 1/16V 100R 300R IN4148 4K7 10n IN4148 IN4148 10K IN4148 SP9680 (7 IN4148 IN4148 IN4148

Appendix A

(Informative appendix) Link encoding example Assume the channel data words are as follows. Bits. 0123 4567 8901 2345 6789 0123 4567 8901 Data. 1100 1010 0101 1111 0000 1100 0011 0000 After conversion. -------------------------------------------------- - Word 4-bit data 5-bit coded data 3 1111 11101 4 0000 11110 5 1100 11010 6 0011 10101 7 0000 11110 The transmitted bitstream is. Bits. 01234 56789 01234 56789 01234 56789 01234 56789 Link (NRZ code). 11010 10110 01011 11101 11110 11010 10101 11110 Link (NRZI code). 01001 10010 00110 10100 10101 10110 01100 10101 Transmission direction Note. The NRZI bitstream shown can also be inverted, with polarity depending on the last bit before.

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