Internet Engineering Task Force (IETF) J. Skoglund
Request for Comments: 8486 Google LLC
Updates: 7845 M. Graczyk
Category: Standards Track October 2018
ISSN: 2070-1721
Internet Engineering Task Force (IETF) J. Skoglund
Request for Comments: 8486 Google LLC
Updates: 7845 M. Graczyk
Category: Standards Track October 2018
ISSN: 2070-1721
Ambisonics in an Ogg Opus Container
Ogg Opus容器中的环境声学
Abstract
摘要
This document defines an extension to the Opus audio codec to encapsulate coded Ambisonics using the Ogg format. It also contains updates to RFC 7845 to reflect necessary changes in the description of channel mapping families.
本文档定义了Opus音频编解码器的扩展，以封装使用Ogg格式的编码双音。它还包含对RFC 7845的更新，以反映通道映射族描述中的必要更改。
Status of This Memo
关于下段备忘
This is an Internet Standards Track document.
这是一份互联网标准跟踪文件。
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。有关互联网标准的更多信息，请参见RFC 7841第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8486.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问https://www.rfc-editor.org/info/rfc8486.
Copyright Notice
版权公告
Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2018 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(https://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Ambisonics with Ogg Opus . . . . . . . . . . . . . . . . . . 3
3.1. Channel Mapping Family 2 . . . . . . . . . . . . . . . . 3
3.2. Channel Mapping Family 3 . . . . . . . . . . . . . . . . 4
3.3. Allowed Numbers of Channels . . . . . . . . . . . . . . . 5
4. Downmixing . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Updates to RFC 7845 . . . . . . . . . . . . . . . . . . . . . 7
5.1. Format of the Channel Mapping Table . . . . . . . . . . . 7
5.2. Unknown Mapping Families . . . . . . . . . . . . . . . . 8
6. Experimental Mapping Families . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Ambisonics with Ogg Opus . . . . . . . . . . . . . . . . . . 3
3.1. Channel Mapping Family 2 . . . . . . . . . . . . . . . . 3
3.2. Channel Mapping Family 3 . . . . . . . . . . . . . . . . 4
3.3. Allowed Numbers of Channels . . . . . . . . . . . . . . . 5
4. Downmixing . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Updates to RFC 7845 . . . . . . . . . . . . . . . . . . . . . 7
5.1. Format of the Channel Mapping Table . . . . . . . . . . . 7
5.2. Unknown Mapping Families . . . . . . . . . . . . . . . . 8
6. Experimental Mapping Families . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
Ambisonics is a representation format for three-dimensional sound fields that can be used for surround sound and immersive virtual-reality playback. See [fellgett75] and [daniel04] for technical details on the Ambisonics format. For the purposes of the this document, Ambisonics can be considered a multichannel audio stream. A separate stereo stream can be used alongside the Ambisonics in a head-tracked virtual reality experience to provide so-called non-diegetic audio -- that is, audio that should remain unchanged by rotation of the listener's head, such as narration or stereo music. Ogg is a general-purpose container, supporting audio, video, and other media. It can be used to encapsulate audio streams coded using the Opus codec. See [RFC6716] and [RFC7845] for technical details on the Opus codec and its encapsulation in the Ogg container, respectively.
Ambisonics是三维声场的表示格式，可用于环绕声和沉浸式虚拟现实播放。有关Ambisonics格式的技术详细信息，请参见[fellgett75]和[daniel04]。在本文档中，环境声学可以被视为多声道音频流。在头部跟踪虚拟现实体验中，单独的立体声流可以与环境音一起使用，以提供所谓的非diegetic音频，即通过听者头部旋转保持不变的音频，如旁白或立体声音乐。Ogg是一个通用容器，支持音频、视频和其他媒体。它可以用来封装使用Opus编解码器编码的音频流。请参见[RFC6716]和[RFC7845]，分别了解Opus编解码器及其在Ogg容器中封装的技术细节。
This document extends the Ogg Opus format by defining two new channel mapping families for encoding Ambisonics. The Ogg Opus format is extended indirectly by adding items with values 2 and 3 to the "Opus Channel Mapping Families" IANA registry. When 2 or 3 are used as the Channel Mapping Family Number in an Ogg stream, the semantic meaning of the channels in the multichannel Opus stream is one of the Ambisonics layouts defined in this document. This mapping can also be used in other contexts that make use of the channel mappings defined by the "Opus Channel Mapping Families" registry.
本文档通过定义两个新的信道映射族来编码双声道，从而扩展了Ogg Opus格式。Ogg Opus格式通过将值为2和3的项添加到“Opus通道映射族”IANA注册表来间接扩展。当2或3用作Ogg流中的频道映射系列号时，多频道Opus流中频道的语义含义是本文档中定义的模糊布局之一。此映射也可用于使用“Opus通道映射系列”注册表定义的通道映射的其他上下文中。
Furthermore, mapping families 240 through 254 (inclusively) are reserved for experimental use.
此外，映射族240到254（包括）保留供实验使用。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“建议”、“不建议”、“可”和“可选”在所有大写字母出现时（如图所示）应按照BCP 14[RFC2119][RFC8174]所述进行解释。
Ambisonics can be encapsulated in the Ogg format by encoding with the Opus codec and setting the channel mapping family value to 2 or 3 in the Ogg identification (ID) header. A demuxer implementation encountering channel mapping family 2 or 3 MUST interpret the Opus stream as containing Ambisonics with the format described in Sections 3.1 or 3.2, respectively.
通过使用Opus编解码器编码并在Ogg标识（ID）报头中将通道映射族值设置为2或3，可以将环境音封装为Ogg格式。遇到信道映射系列2或3的解复用器实现必须将Opus流解释为包含具有第3.1节或第3.2节所述格式的双音信号。
This channel mapping uses the same channel mapping table format used by channel mapping family 1. The output channels are Ambisonic components ordered in Ambisonic Channel Number (ACN) order (which is defined in Figure 1) followed by two optional channels of non-diegetic stereo indexed (left, right). The terms "order" and "degree" are defined according to [ambix].
此通道映射使用与通道映射族1相同的通道映射表格式。输出通道是按Ambisonic通道编号（ACN）顺序排列的Ambisonic组件（在图1中定义），后跟两个非diegetic立体声索引的可选通道（左、右）。术语“顺序”和“程度”根据[ambix]定义。
ACN = n * (n + 1) + m, for order n and degree m.
对于阶数n和阶数m，ACN=n*（n+1）+m。
Figure 1: Ambisonic Channel Number (ACN)
图1：双音通道号（ACN）
For the Ambisonic channels, the ACN component corresponds to channel index as k = ACN. The reverse correspondence can also be computed for an Ambisonic channel with index k.
对于双声道，ACN分量对应于通道索引k=ACN。对于指数为k的双声道，也可以计算反向对应关系。
order n = floor(sqrt(k)), degree m = k - n * (n + 1).
阶数n=floor（sqrt（k）），阶数m=k-n*（n+1）。
Figure 2: Ambisonic Degree and Order from ACN
图2:ACN的混音度和顺序
Note that channel mapping family 2 allows for so-called mixed-order Ambisonic representation, in which only a subset of the full Ambisonic order number of channels is encoded. By specifying the full number in the channel count field, the inactive ACNs can then be indicated in the channel mapping field using the index 255.
请注意，通道映射族2允许所谓的混合阶Ambisonic表示，其中仅对通道的完整Ambisonic阶数的子集进行编码。通过在“通道计数”字段中指定完整数字，可以在“通道映射”字段中使用索引255指示非活动ACN。
Ambisonic channels are normalized with Schmidt Semi-Normalization (SN3D). The interpretation of the Ambisonics signal as well as detailed definitions of ACN channel ordering and SN3D normalization are described in [ambix], Section 2.1.
用施密特半标准化（SN3D）对双音通道进行标准化。在[ambix]第2.1节中描述了环境音信号的解释以及ACN信道顺序和SN3D归一化的详细定义。
In this mapping, C output channels (the channel count) are generated at the decoder by multiplying K = N + M decoded channels with a designated demixing matrix, D, having C rows and K columns (C and K do not have to be equal). Here, N denotes the number of streams encoded, and M is the number of these encoded streams that are coupled to produce two channels. As for channel mapping family 2, this mapping family also allows for the encoding and decoding of full-order Ambisonics and mixed-order Ambisonics, as well as non-diegetic stereo channels. Furthermore, it has the added flexibility of mixing channels. Let X denote a column vector containing K decoded channels X1, X2, ..., XK (from N streams), and let S denote a column vector containing C output streams S1, S2, ..., SC. Then, S = D X, as shown in Figure 3.
在该映射中，通过将K＝N+M个解码信道与具有C行和K列（C和K不必相等）的指定解混矩阵D相乘，在解码器处生成C个输出信道（信道计数）。这里，N表示编码流的数量，M表示耦合以产生两个信道的这些编码流的数量。对于信道映射族2，该映射族还允许对全阶双频和混合阶双频以及非diegetic立体声信道进行编码和解码。此外，它还增加了混合通道的灵活性。让X表示包含K个解码信道X1、X2、…、XK（来自N个流）的列向量，让S表示包含C个输出流S1、S2、…、SC的列向量。然后，S=dx，如图3所示。
/ \ / \ / \
| S1 | | D11 D12 ... D1K | | X1 |
| S2 | | D21 D22 ... D2K | | X2 |
| ... | = | ... ... ... ... | | ... |
| SC | | DC1 DC2 ... DCK | | XK |
\ / \ / \ /
/ \ / \ / \
| S1 | | D11 D12 ... D1K | | X1 |
| S2 | | D21 D22 ... D2K | | X2 |
| ... | = | ... ... ... ... | | ... |
| SC | | DC1 DC2 ... DCK | | XK |
\ / \ / \ /
Figure 3: Demixing in Channel Mapping Family 3
图3：通道映射系列3中的分层
The matrix MUST be provided in the channel mapping table part of the identification header; see Section 5.1.1 of [RFC7845]. The matrix replaces the need for a channel mapping field; for channel mapping family 3, the mapping table has the following layout:
必须在标识头的信道映射表部分提供矩阵；见[RFC7845]第5.1.1节。矩阵取代了通道映射字段的需要；对于通道映射族3，映射表具有以下布局：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
| Stream Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Coupled Count | Demixing Matrix :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
| Stream Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Coupled Count | Demixing Matrix :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Channel Mapping Table for Channel Mapping Family 3
图4：通道映射系列3的通道映射表
The fields in the channel mapping table have the following meaning:
通道映射表中的字段具有以下含义：
1. Stream Count "N" (8 bits, unsigned):
1. 流计数“N”（8位，无符号）：
This is the total number of streams encoded in each Ogg packet.
这是每个Ogg数据包中编码的流的总数。
2. Coupled Stream Count "M" (8 bits, unsigned):
2. 耦合流计数“M”（8位，无符号）：
This is the number of the N streams whose decoders are to be configured to produce two channels (stereo).
这是其解码器将被配置为产生两个信道（立体声）的N个流的数目。
3. Demixing Matrix (16*K*C bits, signed):
3. 分离矩阵（16*K*C位，有符号）：
The coefficients of the demixing matrix stored in column-major order as 16-bit, signed, two's complement fixed-point values with 15 fractional bits (Q15), little endian. If needed, the output gain field can be used for a normalization scale. For mixed-order Ambisonic representations, the silent ACN channels are indicated by all zeros in the corresponding rows of the mixing matrix. This also allows for mixed order with non-diegetic stereo as the number of columns implies the presence of non-diegetic channels.
分频矩阵的系数按列大顺序存储为16位、有符号、2的补定点值和15个小数位（Q15）、小端点。如果需要，输出增益字段可用于标准化刻度。对于混合阶Ambisonic表示，无声ACN通道由混合矩阵对应行中的所有零表示。这也允许非diegetic立体声的混合顺序，因为列数意味着存在非diegetic通道。
Note that [RFC7845] specifies that the identification header cannot exceed one "page", which is 65,025 octets. This limits the Ambisonic order, which then MUST be lower than 12, if full order is utilized and the number of coded streams is the same as the Ambisonic order plus the two non-diegetic channels. The total output channel number, C, MUST be set in the third field of the identification header.
请注意，[RFC7845]指定标识标头不能超过一个“页面”，即65025个八位字节。这限制了Ambisonic顺序，如果使用全顺序，且编码流的数量与Ambisonic顺序加上两个非diegetic通道相同，则Ambisonic顺序必须低于12。必须在标识标头的第三个字段中设置总输出通道号C。
For both channel mapping families 2 and 3, the allowed numbers of channels are (1 + n)^2 + 2j for n = 0, 1, ..., 14 and j = 0 or 1, where n denotes the (highest) Ambisonic order and j denotes whether or not there is a separate non-diegetic stereo stream. This corresponds to periphonic Ambisonics from zeroth to fourteenth order plus potentially two channels of non-diegetic stereo. Explicitly, the allowed number of channels are 1, 3, 4, 6, 9, 11, 16, 18, 25, 27, 36, 38, 49, 51, 64, 66, 81, 83, 100, 102, 121, 123, 144, 146, 169, 171, 196, 198, 225, and 227. Note again that if full Ambisonic order is used and the number of coded streams is the same as the Ambisonic order plus the two non-diegetic channels, the order must then be lower than 12, due to the identification header length limit.
对于通道映射族2和3，对于n=0、1、…、14和j=0或1，允许的通道数为（1+n）^2+2j，其中n表示（最高）双音阶，j表示是否存在单独的非diegetic立体声流。这对应于从第0阶到第14阶的周音环境音加上两个潜在的非diegetic立体声通道。明确地说，允许的信道数量是1、3、4、6、9、11、16、18、25、27、36、38、49、51、64、66、81、83、100、102、121、123、144、146、169、171、196、198、225和227。再次注意，如果使用全Ambisonic顺序，且编码流的数量与Ambisonic顺序加上两个非diegetic通道的数量相同，则由于标识标头长度限制，顺序必须低于12。
The downmixing matrices in this section are only examples known to give acceptable results for stereo downmixing from Ambisonics, but other mixing strategies will be allowed, e.g., to emphasize a certain panning.
本节中的下混音矩阵仅为已知的示例，可给出双声道立体声下混音的可接受结果，但允许使用其他混音策略，例如，强调某一平移。
An Ogg Opus player MAY use the matrix in Figure 5 to implement downmixing from multichannel files using channel mapping families 2 and 3 when there is no non-diegetic stereo. The first and second Ambisonic channels are known as "W" and "Y", respectively. The omitted coefficients in the matrix in the figure have the value 0.0.
当没有非diegetic立体声时，Ogg Opus播放器可以使用图5中的矩阵，使用通道映射族2和3从多通道文件实现下混频。第一和第二双声道分别称为“W”和“Y”。图中矩阵中省略的系数的值为0.0。
/ \ / \ / \
| L | | 0.5 0.5 0.0 ... | | W |
| R | = | 0.5 -0.5 0.0 ... | | Y |
\ / \ / | ... |
\ /
/ \ / \ / \
| L | | 0.5 0.5 0.0 ... | | W |
| R | = | 0.5 -0.5 0.0 ... | | Y |
\ / \ / | ... |
\ /
Figure 5: Stereo Downmixing Matrix for Channel Mapping Families 2 and 3 - Only Ambisonic Channels
图5：通道映射系列2和3的立体声下混频矩阵-仅限双音通道
The first Ambisonic channel (W) is a mono audio stream that represents the average audio signal over all directions. Since W is not directional, Ogg Opus players MAY use W directly for mono playback.
第一个双声道（W）是单声道音频流，表示所有方向上的平均音频信号。由于W不是定向的，Ogg Opus播放器可以直接使用W进行单声道播放。
If a non-diegetic stereo track is present, the player MAY use the matrix in Figure 6 for downmixing. Ls and Rs denote the two non-diegetic stereo channels.
如果存在非diegetic立体声音轨，播放器可以使用图6中的矩阵进行下混音。Ls和Rs表示两个非diegetic立体声通道。
/ \ / \ / \
| L | | 0.25 0.25 0.0 ... 0.5 0.0 | | W |
| R | = | 0.25 -0.25 0.0 ... 0.0 0.5 | | Y |
\ / \ / | ... |
| Ls |
| Rs |
\ /
/ \ / \ / \
| L | | 0.25 0.25 0.0 ... 0.5 0.0 | | W |
| R | = | 0.25 -0.25 0.0 ... 0.0 0.5 | | Y |
\ / \ / | ... |
| Ls |
| Rs |
\ /
Figure 6: Stereo Downmixing Matrix for Channel Mapping Families 2 and 3 - Ambisonic Channels Plus a Non-Diegetic Stereo Stream
图6：通道映射系列2和3的立体声下混频矩阵-双音通道加上非Diegetic立体声流
The language in Section 5.1.1 of [RFC7845] (copied below) implies that the channel mapping table, when present, has a fixed format for all channel mapping families:
[RFC7845]第5.1.1节（复制如下）中的语言意味着通道映射表（如果存在）对所有通道映射族具有固定格式：
The order and meaning of these channels are defined by a channel mapping, which consists of the 'channel mapping family' octet and, for channel mapping families other than family 0, a 'channel mapping table', as illustrated in Figure 3.
这些通道的顺序和意义由通道映射定义，该映射由“通道映射族”八位字节组成，对于非族0的通道映射族，则由“通道映射表”组成，如图3所示。
This document updates [RFC7845] to clarify that the format of the channel mapping table may depend on the channel mapping family:
本文档更新[RFC7845]以澄清通道映射表的格式可能取决于通道映射族：
The order and meaning of these channels are defined by a channel mapping, which consists of the 'channel mapping family' octet and for channel mapping families other than family 0, a 'channel mapping table'.
这些通道的顺序和意义由通道映射定义，该映射由“通道映射族”八位字节组成，对于非族0的通道映射族，则由“通道映射表”定义。
The format of the channel mapping table depends on the channel mapping family. Unless the channel mapping family requires a custom format for its channel mapping table, the RECOMMENDED channel mapping table format for new mapping families is illustrated in Figure 3.
通道映射表的格式取决于通道映射族。除非通道映射族需要其通道映射表的自定义格式，否则新映射族的建议通道映射表格式如图3所示。
The change above is not meant to change how families 1 and 255 currently work. To ensure that, the first paragraph of Section 5.1.1.2 is changed from:
上述更改并不意味着更改族1和255当前的工作方式。为确保将第5.1.1.2节第一段更改为：
Allowed numbers of channels: 1...8. Vorbis channel order (see below).
允许的频道数：1…8。Vorbis通道顺序（见下文）。
to:
致：
Allowed numbers of channels: 1...8, with the mapping specified according to Figure 3. Vorbis channel order (see below).
允许的通道数：1…8，映射根据图3指定。Vorbis通道顺序（见下文）。
Similarly, the first paragraph of Section 5.1.1.3 is changed from:
同样，第5.1.1.3节的第一段更改为：
Allowed numbers of channels: 1...255. No defined channel meaning.
允许的通道数：1…255。没有定义的通道含义。
to:
致：
Allowed numbers of channels: 1...255, with the mapping specified according to Figure 3. No defined channel meaning.
允许的通道数：1…255，映射根据图3指定。没有定义的通道含义。
The treatment of unknown mapping families is changed slightly. Section 5.1.1.4 of [RFC7845] states:
对未知映射族的处理略有改变。[RFC7845]第5.1.1.4节规定：
The remaining channel mapping families (2...254) are reserved. A demuxer implementation encountering a reserved 'channel mapping family' value SHOULD act as though the value is 255.
保留其余的通道映射族（2…254）。遇到保留的“通道映射族”值的解复用器实现应视为该值为255。
This is changed to:
更改为：
The remaining channel mapping families (2...254) are reserved. A demuxer implementation encountering a 'channel mapping family' value that it does not recognize SHOULD NOT attempt to decode the packets and SHOULD NOT use any information except for the first 19 octets of the ID header packet (Figure 2) and the comment header (Figure 10).
保留其余的通道映射族（2…254）。遇到无法识别的“通道映射族”值的解复用器实现不应尝试解码数据包，并且不应使用除ID头数据包（图2）和注释头（图10）的前19个八位字节以外的任何信息。
To make development of new mapping families easier while reducing the risk of creating compatibility issues with non-final versions of mapping families, mapping families 240 through 254 (inclusively) are now reserved for experiments and implementations of in-development families. Note that these mapping-family experiments are not restricted to Ambisonics. Implementers SHOULD attempt to use experimental family numbers that have not recently been used and SHOULD advertise what experimental numbers they use (e.g., for Internet-Drafts).
为了简化新映射族的开发，同时降低与映射族的非最终版本产生兼容性问题的风险，映射族240到254（含）现在保留用于开发中族的实验和实现。请注意，这些映射族实验并不局限于双声道。实施者应尝试使用最近未使用过的实验性家庭编号，并应宣传他们使用的实验性编号（例如，用于互联网草稿）。
The Ambisonics mapping experiments that led to this document used experimental family 254 for family 2 and experimental family 253 for family 3.
导致本文件的双音映射实验将实验族254用于族2，将实验族253用于族3。
Implementations of the Ogg container need to take appropriate security considerations into account, as outlined in Section 8 of [RFC7845]. The extension defined in this document requires that semantic meaning be assigned to more channels than the existing Ogg format requires. Since more allocations will be required to encode and decode these semantically meaningful channels, care should be taken in any new allocation paths. Implementations MUST NOT overrun their allocated memory nor read from uninitialized memory when managing the Ambisonic channel mapping.
Ogg容器的实现需要考虑适当的安全因素，如[RFC7845]第8节所述。本文档中定义的扩展要求将语义分配给比现有Ogg格式要求更多的通道。由于需要更多的分配来编码和解码这些语义上有意义的信道，因此在任何新的分配路径中都应小心。在管理Ambisonic通道映射时，实现不得超出其分配的内存，也不得从未初始化的内存中读取。
IANA has added 17 new assignments to the "Opus Channel Mapping Families^a registry.
IANA在“Opus Channel Mapping Families^a”注册表中添加了17项新任务。
+---------+----------------------+----------------------------------+
| Value | Description | Reference |
+---------+----------------------+----------------------------------+
| 0 | Mono, L/R stereo | Section 5.1.1.1 of [RFC7845], |
| | | Section 5 of this document |
| | | |
| 1 | 1-8 channel surround | Section 5.1.1.2 of [RFC7845], |
| | | Section 5 of this document |
| | | |
| 2 | Ambisonics as | Section 3.1 of this document |
| | individual channels | |
| | | |
| 3 | Ambisonics with | Section 3.2 of this document |
| | demixing matrix | |
| | | |
| 240-254 | Experimental use | Section 6 of this document |
| | | |
| 255 | Discrete channels | Section 5.1.1.3 of [RFC7845], |
| | | Section 5 of this document |
+---------+----------------------+----------------------------------+
+---------+----------------------+----------------------------------+
| Value | Description | Reference |
+---------+----------------------+----------------------------------+
| 0 | Mono, L/R stereo | Section 5.1.1.1 of [RFC7845], |
| | | Section 5 of this document |
| | | |
| 1 | 1-8 channel surround | Section 5.1.1.2 of [RFC7845], |
| | | Section 5 of this document |
| | | |
| 2 | Ambisonics as | Section 3.1 of this document |
| | individual channels | |
| | | |
| 3 | Ambisonics with | Section 3.2 of this document |
| | demixing matrix | |
| | | |
| 240-254 | Experimental use | Section 6 of this document |
| | | |
| 255 | Discrete channels | Section 5.1.1.3 of [RFC7845], |
| | | Section 5 of this document |
+---------+----------------------+----------------------------------+
[ambix] Nachbar, C., Zotter, F., Deleflie, E., and A. Sontacchi, "AMBIX - A SUGGESTED AMBISONICS FORMAT", Ambisonics Symposium, June 2011, <http://iem.kug.ac.at/fileadmin/media/iem/projects/2011/ ambisonics11_nachbar_zotter_sontacchi_deleflie.pdf>.
[ambix]Nachbar，C.，Zotter，F.，Deleflie，E.，和A.Sontacchi，“ambix-建议的AMBISONICS格式”，AMBISONICS研讨会，2011年6月<http://iem.kug.ac.at/fileadmin/media/iem/projects/2011/ ambisonics11\u nachbar\u zotter\u sontacchi\u deleflie.pdf>。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，DOI 10.17487/RFC2119，1997年3月<https://www.rfc-editor.org/info/rfc2119>.
[RFC6716] Valin, JM., Vos, K., and T. Terriberry, "Definition of the Opus Audio Codec", RFC 6716, DOI 10.17487/RFC6716, September 2012, <https://www.rfc-editor.org/info/rfc6716>.
[RFC6716]Valin，JM.，Vos，K.，和T.Terriberry，“作品音频编解码器的定义”，RFC 6716，DOI 10.17487/RFC6716，2012年9月<https://www.rfc-editor.org/info/rfc6716>.
[RFC7845] Terriberry, T., Lee, R., and R. Giles, "Ogg Encapsulation for the Opus Audio Codec", RFC 7845, DOI 10.17487/RFC7845, April 2016, <https://www.rfc-editor.org/info/rfc7845>.
[RFC7845]Terriberry，T.，Lee，R.，和R.Giles，“Opus音频编解码器的Ogg封装”，RFC 7845，DOI 10.17487/RFC78452016年4月<https://www.rfc-editor.org/info/rfc7845>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8174]Leiba，B.，“RFC 2119关键词中大写与小写的歧义”，BCP 14，RFC 8174，DOI 10.17487/RFC8174，2017年5月<https://www.rfc-editor.org/info/rfc8174>.
[daniel04] Daniel, J. and S. Moreau, "Further Study of Sound Field Coding with Higher Order Ambisonics", Audio Engineering Society Convention Paper, May 2004, <https://www.researchgate.net/publication/ 277841868_Further_Study_of_Sound_Field_Coding _with_Higher_Order_Ambisonics>.
[daniel04]Daniel，J.和S.Moreau，“用高阶双声学进一步研究声场编码”，音频工程学会会议论文，2004年5月<https://www.researchgate.net/publication/ 277841868 \u进一步研究\u声场\u编码\u与\u高阶\u双音学>。
[fellgett75] Fellgett, P., "Ambisonics. Part one: General system description", Studio Sound vol. 17, no. 8, pp. 20-22, August 1975, <http://www.michaelgerzonphotos.org.uk/articles/ Ambisonics%201.pdf>.
[fellgett75]Fellgett，P.，“双声学.第一部分：一般系统描述”，《录音棚声音》第17卷，第8期，第20-22页，1975年8月<http://www.michaelgerzonphotos.org.uk/articles/ Ambisonics%201.pdf>。
Acknowledgments
致谢
Thanks to Timothy Terriberry, Jean-Marc Valin, Mark Harris, Marcin Gorzel, and Andrew Allen for their guidance and valuable contributions to this document.
感谢Timothy Terriberry、Jean-Marc Valin、Mark Harris、Marcin Gorzel和Andrew Allen对本文件的指导和宝贵贡献。
Authors' Addresses
作者地址
Jan Skoglund Google LLC 345 Spear Street San Francisco, CA 94105 United States of America
Jan Skoglund Google LLC 345矛街旧金山，CA 94105美利坚合众国
Email: jks@google.com
Email: jks@google.com
Michael Graczyk
迈克尔·格拉奇克
Email: michael@mgraczyk.com
Email: michael@mgraczyk.com