payloads.sgml

ORTP开源的rtp库

<refentry id="ortp-RTP-payloads-and-profiles">
<refmeta>
<refentrytitle id="top_of_page">RTP payloads and profiles</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>ORTP Library</refmiscinfo>
</refmeta>

<refnamediv>
<refname>RTP payloads and profiles</refname>
<refpurpose>This section describes the way that the oRTP stack manages RTP profiles and payload types.</refpurpose>
<!--[<xref linkend="desc" endterm="desc.title"/>]-->
</refnamediv>

<refsynopsisdiv id="synopsis">
<title id="synopsis.title">Synopsis</title>

<synopsis>

#include &lt;payloadtype.h&gt;


            <link linkend="PayloadType">PayloadType</link>;
            <link linkend="RtpProfile">RtpProfile</link>;
<link linkend="void">void</link>        <link linkend="rtp-profile-clear-all">rtp_profile_clear_all</link>           (<link linkend="RtpProfile">RtpProfile</link> *prof);
#define     <link linkend="rtp-profile-get-name">rtp_profile_get_name</link>            (profile)
<link linkend="void">void</link>        <link linkend="rtp-profile-set-name">rtp_profile_set_name</link>            (<link linkend="RtpProfile">RtpProfile</link> *prof,
                                             const <link linkend="char">char</link> *name);
<link linkend="void">void</link>        <link linkend="rtp-profile-set-payload">rtp_profile_set_payload</link>         (<link linkend="RtpProfile">RtpProfile</link> *prof,
                                             <link linkend="int">int</link> index,
                                             <link linkend="PayloadType">PayloadType</link> *pt);
#define     <link linkend="rtp-profile-clear-payload">rtp_profile_clear_payload</link>       (profile,index)
</synopsis>
</refsynopsisdiv>









<refsect1 id="desc">
<title id="desc.title">Description</title>
<para>
A rtp payload type is a number between 0 and 127 that identifies a particular payload 
(GSM, PCMU, MPEG,...) within a given rtp profile. The <link linkend="PayloadType"><type>PayloadType</type></link> object in oRTP describes
a payload.

An RTP profile is a table that assigns particular payloads (GSM, MPEG...) to a payload type
number within the range 0..127. In oRTP, profiles are represented by the <link linkend="RtpProfile"><type>RtpProfile</type></link> object.

For example in the AV profile (Audio Video profile, defined in RFC1890), often used 
by telephony applications, the payload type number 8 is assigned to PCMA 
(A-law compressed audio) at sampling frequency 8000 Hz, mono.

By default, all RTP sessions created by oRTP use the AV profile, but you can change the profile
of an RTP session using <link linkend="rtp-session-set-profile"><function>rtp_session_set_profile()</function></link>.
</para>
</refsect1>

<refsect1 id="details">
<title id="details.title">Details</title>
<refsect2>
<title><anchor id="PayloadType" role="struct">PayloadType</title>
<indexterm><primary>PayloadType</primary></indexterm><programlisting>typedef struct {
	int type;
	#define PAYLOAD_AUDIO_CONTINUOUS 0
	#define PAYLOAD_AUDIO_PACKETIZED 1
	#define	PAYLOAD_VIDEO 2
	#define PAYLOAD_OTHER 3  /* ?? */
	int clock_rate;
	char bits_per_sample;		/* in case of continuous audio data */
	char *zero_pattern;
	int pattern_length;
	/* other useful information for the application*/
	int normal_bitrate;	/*in bit/s */
	char *mime_type;
	char *recv_fmtp; /* various format parameters for the incoming stream */
	char *send_fmtp; /* various format parameters for the outgoing stream */
	int flags;
	void *user_data;
} PayloadType;
</programlisting>
<para>

</para></refsect2>
<refsect2>
<title><anchor id="RtpProfile" role="struct">RtpProfile</title>
<indexterm><primary>RtpProfile</primary></indexterm><programlisting>typedef struct {
	char *name;
	PayloadType *payload[RTP_PROFILE_MAX_PAYLOADS];
} RtpProfile;
</programlisting>
<para>

</para></refsect2>
<refsect2>
<title><anchor id="rtp-profile-clear-all" role="function">rtp_profile_clear_all ()</title>
<indexterm><primary>rtp_profile_clear_all</primary></indexterm><programlisting><link linkend="void">void</link>        rtp_profile_clear_all           (<link linkend="RtpProfile">RtpProfile</link> *prof);</programlisting>
<para>
Initialize the profile to the empty profile (all payload type are unassigned).</para>
<para>

</para><variablelist role="params">
<varlistentry><term><parameter>prof</parameter>&nbsp;:</term>
<listitem><simpara>


</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="rtp-profile-get-name" role="macro">rtp_profile_get_name()</title>
<indexterm><primary>rtp_profile_get_name</primary></indexterm><programlisting>#define rtp_profile_get_name(profile) 	(const char*)((profile)-&gt;name)
</programlisting>
<para>
</para>
<para>

</para><variablelist role="params">
<varlistentry><term><parameter>profile</parameter>&nbsp;:</term>
<listitem><simpara>		a rtp profile object (<link linkend="RtpProfile"><type>RtpProfile</type></link>)
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="rtp-profile-set-name" role="function">rtp_profile_set_name ()</title>
<indexterm><primary>rtp_profile_set_name</primary></indexterm><programlisting><link linkend="void">void</link>        rtp_profile_set_name            (<link linkend="RtpProfile">RtpProfile</link> *prof,
                                             const <link linkend="char">char</link> *name);</programlisting>
<para>
Set a name to the rtp profile. (This is not required)</para>
<para>

</para><variablelist role="params">
<varlistentry><term><parameter>prof</parameter>&nbsp;:</term>
<listitem><simpara>
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>name</parameter>&nbsp;:</term>
<listitem><simpara>


</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="rtp-profile-set-payload" role="function">rtp_profile_set_payload ()</title>
<indexterm><primary>rtp_profile_set_payload</primary></indexterm><programlisting><link linkend="void">void</link>        rtp_profile_set_payload         (<link linkend="RtpProfile">RtpProfile</link> *prof,
                                             <link linkend="int">int</link> index,
                                             <link linkend="PayloadType">PayloadType</link> *pt);</programlisting>
<para>
Assign payload type number <parameter>index</parameter> to payload type desribed in <parameter>pt</parameter> for the RTP profile
<parameter>profile</parameter>.</para>
<para>

</para><variablelist role="params">
<varlistentry><term><parameter>prof</parameter>&nbsp;:</term>
<listitem><simpara>
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>index</parameter>&nbsp;:</term>
<listitem><simpara>	the payload type number
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>pt</parameter>&nbsp;:</term>
<listitem><simpara>		the payload type description (a <link linkend="PayloadType"><type>PayloadType</type></link> object )
</simpara></listitem></varlistentry>
</variablelist></refsect2>
<refsect2>
<title><anchor id="rtp-profile-clear-payload" role="macro">rtp_profile_clear_payload()</title>
<indexterm><primary>rtp_profile_clear_payload</primary></indexterm><programlisting>#define rtp_profile_clear_payload(profile,index)	rtp_profile_set_payload(profile,index,NULL)	
</programlisting>
<para>
Set payload type number <parameter>index</parameter> unassigned in profile <parameter>profile</parameter>.</para>
<para>

</para><variablelist role="params">
<varlistentry><term><parameter>profile</parameter>&nbsp;:</term>
<listitem><simpara>	an RTP profile (a <link linkend="RtpProfile"><type>RtpProfile</type></link> object)
</simpara></listitem></varlistentry>
<varlistentry><term><parameter>index</parameter>&nbsp;:</term>
<listitem><simpara>	the payload type number
</simpara></listitem></varlistentry>
</variablelist></refsect2>

</refsect1>



<refsect1>
<title>See Also</title>
<para>
<link linkend="rtp-session-set-profile"><function>rtp_session_set_profile()</function></link>
</para>
</refsect1>

</refentry>