manual.lyx

一个开源的sip源代码

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Asks decoder to set perceptual enhancement off (0) or on(1)
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Asks (if 1) the encoder to be less 
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agressive
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 due to high packet loss
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Asks encoder to switch to mode N
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Asks encoder to switch to mode N for low-band
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Asks encoder to switch to mode N for high-band
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Asks encoder to switch to quality N for VBR
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Request acknowloedge (0=no, 1=all, 2=only for in-band data)
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Asks encoder to set CBR (0), VAD(1), DTX(3), VBR(5), VBR+DTX(7)
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Transmit (8-bit) character to the other end
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Intensity stereo information
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Announce maximum bit-rate acceptable (N in bytes/second)
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reserved
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Acknowledge receiving packet N
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reserved
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</lyxtabular>

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\begin_layout Caption
In-band signalling codes
\begin_inset LatexCommand \label{cap:In-band-signalling-codes}

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Finally, applications may define custom in-band messages using mode 13.
 The size of the message in bytes is encoded with 5 bits, so that the decoder
 can skip it if it doesn't know how to interpret it.
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\newpage

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\begin_layout Chapter
Formats and standards
\begin_inset LatexCommand \index{standards}

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\begin_inset LatexCommand \label{sec:Formats-and-standards}

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\begin_layout Standard
Speex can encode speech in both narrowband and wideband and provides different
 bit-rates.
 However, not all features need to be supported by a certain implementation
 or device.
 In order to be called 
\begin_inset Quotes eld
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Speex compatible
\begin_inset Quotes erd
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 (whatever that means), an implementation must implement at least a basic
 set of features.
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At the minimum, all narrowband modes of operation MUST be supported at the
 decoder.
 This includes the decoding of a wideband bit-stream by the narrowband decoder
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status collapsed

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The wideband bit-stream contains an embedded narrowband bit-stream which
 can be decoded alone
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.
 If present, a wideband decoder MUST be able to decode a narrowband stream,
 and MAY either be able to decode all wideband modes or be able to decode
 the embedded narrowband part of all modes (which includes ignoring the
 high-band bits).
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For encoders, at least one narrowband or wideband mode MUST be supported.
 The main reason why all encoding modes do not have to be supported is that
 some platforms may not be able to handle the complexity of encoding in
 some modes.
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\begin_layout Section
RTP
\begin_inset LatexCommand \index{RTP}

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 Payload Format 
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The RTP payload draft is included in appendix 
\begin_inset LatexCommand \ref{sec:IETF-draft}

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 and the latest version is available at 
\begin_inset LatexCommand \url{http://www.speex.org/drafts/latest}

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.
 This draft has been sent (2003/02/26) to the Internet Engineering Task
 Force (IETF) and will be discussed at the March 18th meeting in San Francisco.
 
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\begin_layout Section
MIME Type
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For now, you should use the MIME type audio