RFC4733 RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals

   This memo describes how to carry dual-tone multifrequency (DTMF)
   signalling, other tone signals, and telephony events in RTP packets.
   It obsoletes RFC 2833.

本文描述了如何运载双音多频信号，其它的声音信号，还有在RTP包中的电话事件。它取代了RFC2833。

   This memo captures and expands upon the basic framework defined in
   RFC 2833, but retains only the most basic event codes.  It sets up an
   IANA registry to which other event code assignments may be added.
   Companion documents add event codes to this registry relating to
   modem, fax, text telephony, and channel-associated signalling events.
   The remainder of the event codes defined in RFC 2833 are
   conditionally reserved in case other documents revive their use.
本文基于RFC2833中的基本框架进行了扩展。 但是保留了大部分基本的事件代码。它建立了一个IANA注册，用于增加其它的事件代码。类似的文档将modem，传真，文字电话，和通道相关的信令事件。在RFC2833中定义的其它代码事件将继续保留，这样相关的文档可以继续使用。

   This document provides a number of clarifications to the original
   document.  However, it specifically differs from RFC 2833 by removing
   the requirement that all compliant implementations support the DTMF
   events.  Instead, compliant implementations taking part in
   out-of-band negotiations of media stream content indicate what events
   they support.  This memo adds three new procedures to the RFC 2833
   framework: subdivision of long events into segments, reporting of
   multiple events in a single packet, and the concept and reporting of
   state events.

本文档相对原来的文档提供了一些澄清。它与RFC2833的区别是移除了所有应用支持DTMF的限制。取而代之的是，在兼容应用加入带外媒体流内容协商表示她们支持什么样的事件。本文档针对RFC2833增加了3个新的流程。1）将长的事件分开到片段中，2）在一个包中报告多个事件，3）状态事件的概念和汇报。