1、 1 Scope 1.1 This standard defines the mapping of AES digital audio data, AES auxiliary data, and associated control information into the ancillary data space of serial digital video conforming to ANSI/SMPTE 259M or SMPTE 344M. The audio data and auxiliary data are derived from AES3, hereafter refer
2、red to as AES audio. The AES audio data may contain linear PCM audio or non-PCM data formatted according to SMPTE 337M. 1.2 Audio sampled at 48 kHz and clock locked (synchronous) to video is the preferred implementation for intrastudio applications. As an option, this standard supports AES audio at
3、synchronous or asynchronous sampling rates from 32 kHz to 48 kHz. 1.3 The minimum, or default, operation of this standard supports 20 bits of audio data as defined in clause 3.5. As an option, this standard supports 24-bit audio or four bits of AES auxiliary data as defined in clause 3.10. 1.4 This
4、standard provides a minimum of two audio channels and a maximum of 16 audio channels based on available ancillary data space in a given format (four channels maximum for composite digital). Audio channels are transmitted in pairs combined, where appropriate, into groups of four. Each group is identi
5、fied by a unique ancillary data ID. 1.5 Several modes of operation are defined and letter suffixes are applied to the nomenclature for this standard to facilitate convenient identification of interoperation between equipment with various capabilities. The default form of operation is 48-kHz synchron
6、ous audio sampling carrying 20 bits of AES audio data and defined in a manner to ensure reception by all equipment conforming to this standard. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time
7、 of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent edition of the standards indicated below. AES3-2003, AES standard for Digital Audio Di
8、gital Input-Output Interfacing Serial Transmission Format for Two-Channel Linearly Represented Digital Audio Data (AES3) ANSI/SMPTE 259M-1997, Television 10-Bit 4:2:2 Component and 4fsc NTSC Composite Digital Signals Serial Digital Interface SMPTE 291M-1998, Television Ancillary Data Packet and Spac
9、e Formatting Page 1 of 17 pages SMPTE 272M-2004 Revision of ANSI/SMPTE 272M-1994 Copyright 2004 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., White Plains, NY 10607 (914) 761-1100 SMPTE STANDARD for Television Formatting AES Audio and Auxiliary Data into Digital Vi
10、deo Ancillary Data Space Approved April 7, 2004 SMPTE 272M-2004 Page 2 of 17 pages SMPTE 337M-2000, Television Format for Non-PCM Audio and Data in an AES3 Serial Digital Audio Interface SMPTE 344M-2000, Television 540 Mb/s Serial Digital Interface SMPTE RP 165-1994, Error Detection Checkwords and S
11、tatus Flags for Use in Bit-Serial Digital Interfaces for Television SMPTE RP 168-2002, Definition of Vertical Interval Switching Point for Synchronous Video Switching 3 Definition of terms 3.1 AES audio: All the VUCP data, audio data and auxiliary data, associated with one AES digital stream as defi
12、ned in AES3. 3.2 AES frame: Two AES subframes, one with audio data for channel 1 followed by one with audio data for channel 2. 3.3 AES subframe: All data associated with one AES audio sample for one channel in a channel pair. 3.4 audio control packet: An ancillary data packet occurring once a field
13、 in an interlaced system (once a frame in a progressive system) and containing data used in the operation of optional features of this standard. 3.5 audio data: 23 bits: 20 bits of AES audio associated with one audio sample, not including AES auxiliary data, plus the following 3 bits: sample validit
14、y (V bit), channel status (C bit), and user data (U bit). 3.6 audio data packet: An ancillary data packet containing audio data for 1 or 2 channel pairs (2 or 4 channels). An audio data packet may contain audio data for one or more samples associated with each channel. 3.7 audio frame number: A numb
15、er, starting at 1, for each frame within the audio frame sequence. For the example in 3.8, the frame numbers would be 1, 2, 3, 4, 5. 3.8 audio frame sequence: The number of video frames required for an integer number of audio samples in synchronous operation. As an example: the audio frame sequence
16、for synchronous 48-kHz sampling in an 30/1.001 frame/s system is 5 frames. 3.9 audio group: Consists of one or two channel pairs which are contained in one ancillary data packet. Each audio group has a unique ID as defined in clause 12.2. Audio groups are numbered 1 through 4. 3.10 auxiliary data: F
17、our bits of AES audio associated with one sample defined as auxiliary data by AES3. The four bits may be used to extend the resolution of audio sample. 3.11 channel pair: Two digital audio channels, generally derived from the same AES audio source. 3.12 data ID: A word in the ancillary data packet w
18、hich identifies the use of the data therein. 3.13 extended data packet: An ancillary data packet containing auxiliary data corresponding to, and immediately following, the associated audio data packet. 3.14 sample pair: Two samples of AES audio as defined in clause 3.1. 3.15 synchronous audio: Audio
19、 is defined as being clock synchronous with video if the sampling rate of audio is such that the number of audio samples occurring within an integer number of video frames is itself a constant integer number, as in the following examples: SMPTE 272M-2004 Page 3 of 17 pages Audio sampling rate Sample
20、s/frame, 30/1.001 fr/s video Samples/frame, 25 fr/s video 48.0 kHz 8008/5 1920/1 44.1 kHz 147147/100 1764/1 32.0 kHz 16016/15 1280/1 AES11 provides specific recommendations for audio and video synchronization. NOTE The video and audio clocks must be derived from the same source since simple frequenc
21、y synchronization could eventually result in a missing or extra sample within the audio frame sequence. 4 Overview and levels of operation 4.1 Audio data derived from one or more AES frames and one or two channel pairs are configured in an audio data packet as shown in figure 1. Generally, both chan
22、nels of a channel pair will be derived from the same AES audio source; however, this is not required. The number of samples per channel contained in one audio data packet will depend on the distribution of the data in a video field. As an example, the ancillary data space in some television lines ma
23、y carry three samples, some may carry four samples. Other values are possible. Ancillary data space carrying no samples will not have an audio data packet. NOTE Receiver designers should recognize that some existing transmission equipment may transmit other sample counts, including zero. Receivers s
24、hould handle correctly sample counts from zero to the limits of ancillary data space and receive buffer space. 4.2 Three types of ancillary data packets to carry AES audio information are defined. The audio data packet carries all the information in the AES bit stream excluding the auxiliary data de
25、fined by AES3. The audio data packet is located in the ancillary data space of the digital video on most of the television lines in a field. An audio control packet is transmitted once per field in an interlaced system and once per frame in a progressive system. The audio control packet is optional
26、for the default case of 48-kHz synchronous audio (20 or 24 bits), and is required for all other modes of operation. Auxiliary data are carried in an extended data packet corresponding to and immediately following the associated audio data packet. 4.3 Data IDs (see clauses 12.2, 13.1, and 14.1) are d
27、efined for four separate packets of each packet type. This allows for up to eight channel pairs in component video; however, there is ancillary data space for only two channel pairs (of 20 or 24 bit, 48-kHz audio) in composite video. In this standard, the audio groups are numbered 1 through 4 and th
28、e channels are numbered 1 through 16. Channels 1 through 4 are in group 1, channels 5 through 8 are in group 2, and so on. 4.4 If extended data packets are used, they are included on the same video line as the audio data packet which contains data from the same sample pair. The extended data packet
29、follows the audio data packet and contains two 4-bit groups of auxiliary data per ancillary data word as shown in figure 1. 4.5 To define the level of support in this standard by a particular equipment, a suffix letter is added to the standard number. The default compliance is defined as level A and
30、 implements synchronous audio sampled at 48 kHz and carrying only the (20-bit) audio data packets. Distribution of samples on the television lines for level A specifically follows the uniform sample distribution as required by clause 9.1 in order to ensure interoperation with receivers limited to le
31、vel A operation (see annex A for distribution analysis). 4.6 Levels of operation indicate support as listed: A) Synchronous audio at 48 kHz, 20-bit audio data packets (allows receiver operation with a buffer size less than the 64 samples required by clause 9.2); SMPTE 272M-2004 Page 4 of 17 pages B)
32、 Synchronous audio at 48 kHz, for use with composite digital video signals, sample distribution to allow extended data packets, but not utilizing those packets (requires receiver operation with a buffer size of 64 samples per clause 9.2); C) Synchronous audio at 48 kHz, audio and extended data packe
33、ts; D) Asynchronous audio (48 kHz implied, other frequencies if so indicated); E) 44.1-kHz audio; F) 32-kHz audio; G) 32-kHz to 48-kHz continuous sampling rate range; H) Audio frame sequence (see clause 14.2); I) Time delay tracking; J) Non-coincident Z bits in a channel pair. 4.7 Examples of compli
34、ance nomenclature: A transmitter that supports only 20-bit 48-kHz synchronous audio would be said to conform to SMPTE 272M-A. (Transmitted sample distribution is expected to conform to clause 9.) A transmitter that supports 20-bit and 24-bit 48-kHz synchronous audio would be said to conform to SMPTE
35、 272M-ABC. (In the case of level A operation, the transmitted sample distribution is expected to conform to clause 9, although a different sample distribution may be used when it is in operation conforming to levels B or C.) A receiver which can only accept 20-bit 48-kHz synchronous audio and requir
36、ing level A sample distribution would be said to conform to SMPTE 272M-A. A receiver which only utilizes the 20-bit data but can accept the level B sample distribution would be said to conform to SMPTE 272M-AB since it will handle either sample distribution. A receiver which accepts and utilizes the
37、 24-bit data would be said to conform to SMPTE 272M-C. Equipment that supports only asynchronous audio and only at 32 kHz, 44.1 kHz, and 48 kHz would be said to conform to SMPTE 272M-DEF. NOTE Implementations of this standard may achieve synchronous or asynchronous operation through the use of sampl
38、e rate converters. Documented compliance levels for products should reference how AES audio is mapped into the ancillary data space only. It is recommended that product manufacturers clearly state when sample rate conversion is used to support multiple sample rates and/or asynchronous operation. It
39、is also recommended that the use of sample rate conversion be user selectable. For example, when the AES audio data contains SMPTE 337M formatted data the use of sample rate conversion will corrupt the 337M data (see Annex B). This recommendation applies to both multiplexing (embedding) and demultip
40、lexing (receiving) devices. SMPTE 272M-2004 Page 5 of 17 pages Auxiliary Data 4 bits20 bits Sample DataSubframe 2 (channel 2)AES Channel-Pair 1AES Subframe 32 bitsPreamble X, Y, or Z, 4 bitsAudio Data PacketFrame 0YChannel 2Subframe 1 Subframe 2AES Channel-Pair 2ZChannel 1YChannel 2XChannel 1YChanne
41、l 2Frame 1Frame 191Frame 0YChannel 2Subframe 1 Subframe 2AES Channel-Pair 1ZChannel 1YChannel 2XChannel 1YChannel 2Frame 1Frame 191 Frame 2Subframe parityAudio channel statusUser bit dataAudio sample validityAES 1, Chnl 1Channel 1x, x+1, x+2AES 1, Chnl 2Channel 2x, x+1, x+2AES 2, Chnl 1Channel 3x, x
42、+1, x+2DataCountDataBlkNumDataIDCheckSumAUXDataCountDataBlkNumDataIDCheckSum20 + 3 bits of data is mappedinto 3 ANC wordsPrecedes associated extended data packet4 bits of data contained in 1Extended Data Packet word2 groups of 4 bitsmapped into 1 wordAUXAUXAUXAUXAUXExtended Data PacketFollows associ
43、ated audio data packetData HeaderComposite, 3FCComponent, 000 3FF 3FF1 word contains theauxiliary data for 2samplesVUCPAUXPreambleNOTE - See clause 15 and SMPTE 291M for ancillary data packet formatting Figure 1 Relation between AES data and audio extended data packets SMPTE 272M-2004 Page 6 of 17 p
44、ages 5 Use of ancillary data space 5.1 For component video, audio and extended data shall be located in the data space between EAV and SAV (HANC) and may be on any line allowed by this standard. 5.2 For composite video, audio and extended data packets may be located in any ancillary data space, exce
45、pt that audio data shall not be present during equalizing pulses. 5.3 Audio and extended data shall not be transmitted during the horizontal ancillary data space following the normal video switching point; that is, the first horizontal interval subsequent to the switched line (see SMPTE RP 168). 5.4
46、 Audio and extended data are not transmitted during the portion of the horizontal ancillary data space designated for error detection check-words defined in SMPTE RP 165. NOTE Receiver designers should recognize that some existing transmission equipment may not conform to the restrictions of clauses
47、 5.2 through 5.4. Receivers should receive audio data transmitted in any ancillary data space. 5.5 In accordance with SMPTE 291M audio and extended data should be inserted immediately after the digital synchronization data (EAV or TRS-ID) in the available ancillary data space. For composite video, i
48、n the special case of the second vertical sync pulse in a television line, audio data shall be inserted at the earliest sample designated as ancillary data space (word 340 for 30/1.001 frame/s video rates, word 404 for 25 frame/s video rates). 6 Audio data packet formatting 6.1 The four audio channe
49、ls from audio group 1 are ordered such that channels 1 and 2 make one channel pair and channels 3 and 4 make another. Audio group 2 contains channels 5 and 6 as one channel pair, and so on. 6.2 Where the audio data are derived from a single AES data stream, the data shall be ordered such that data from a subframe 1 is always transmitted before the data from a subframe 2 in the same channel pair. This means that data from subframe 1 would be placed in channel 1 (or 3, 5, .) and data from subframe 2 would be placed in channel 2 (or 4, 6, .). 6.3 The order tha
