RtpApp

RTP Application Configuration

The RTP Application generates the outbound RTP packet streams, under the direct instruction of another app such as the SrpSipApp, or the LhoSipApp (internal announcement mode).

A typical configuration will consist of a single SrpSipApp which directs multiple copies of the RtpApp. This is done by setting the repeat count on the RtpApp application. Each RtpApp executes as an independent process, which provides multi-core scalability for the CPU-intensive and real-time-critical work associated with generating outbound RTP audio and (as necessary) performing DTMF wave-filter analysis of inbound RTP audio.

The RtpApp performs the related codec tasks. Specifically the RtpApp will:

1. Negotiate the codec selection, based on the codecs which it is configured to support.
2. Read the coded audio packets from disk or database and stream them.
3. Generate silence packets appropriate for the specified codec.
4. Decode received audio packets for the purpose of DTMF detection.

Here is a config example which starts-up 6 copies of the RtpApp, each of which will perform audio packet streaming for up to 40 simultaneous RTP streams.

    <?xml version="1.0" encoding="utf-8"?>
    <n2svcd>
      ...
      <applications>
        ...
        <application name="RTP" module="RtpApp" repeat="6">
          <include>
            <lib>../../n2sip/apps/srp/lib</lib>
            <lib>../../n2sip/lib</lib>
            <lib>../apps/db/lib</lib>
          </include>
          <parameters>
            <parameter name="trace_level" value="1"/>
            <parameter name="edr_enabled" value="1"/>
            <parameter name="rtp_streams_per_app" value="40"/>
            <parameter name="rtp_start_port" value="6970"/>
            <parameter name="rtp_local_ip" value="192.168.1.5"/>

            <parameter name="rtp_audio_encodings" value="PCMU/8000,PCMA/8000"/>
            <parameter name="rtp_dtmf_inband_supported" value="no"/>
            <parameter name="rtp_event_sendonly" value="0"/>
            <parameter name="leading_silence" value="40"/>

            <parameter name="audio_dir" value="../../n2sip/demo/audio/ulaw"/>
            <!-- <parameter name="db_app_name" value="DB-AUDIO"/> -->
            <!-- <parameter name="db_sql_set" value="simple"/> -->
          </parameters>
          <config>
            <!-- Internal RTP announcement languages. -->
            <languages>
              <language name="English" default="1"/>
              <language name="German"/>
            </languages>
          </config>
        </application>
        ...
      </application>
      ...
    </n2svcd>

Configuration Details

The application element attributes for an RTP Application instance may include the below.

For details of the various parameter types used, refer to Common Configuration.

Language Names

Each language name definition defines a known language name.

• For internal announcements, these must be the exact name which matches the language name in the mapping.json file which is used to transform “Message ID” + “Language” → “Audio Filenames”.
• For internal announcements using variable parts, these must be the exact name which matches the SIP Language Codec name.
• For external SRP announcements, this name must match an entry in the Language MAP used for that SRP.

Names must be unique. Only one name may be marked as default.

Each language Object in the config.languages Array is configured as follows.

The language name English is always added if not present.

If no language is configured as default, then the English language will be marked as the default.

SQL SELECT Sets

Each SQL SELECT set has the following bind parameters and return row keys.

SET n2srp.v1

This default set is:

SELECT announcement_id, language_name, play_list FROM announcement a
    INNER JOIN language l ON l.language_id = a.language_id WHERE resource_id = ?"

SELECT content AS audio_stream FROM n2srp.audio_file f
  JOIN n2srp.audio_file_version v USING (audio_file_id)
  JOIN n2srp.language l USING (language_id)
  JOIN n2srp.audio_file_encoding e USING (audio_file_encoding_id)
  JOIN n2srp.audio_file_content c USING (content_md5_hash)
WHERE
  f.announcement_set_id = (SELECT announcement_set_id FROM n2srp.announcement_set WHERE type_of_set = 'active')
  AND l.language_name = ? AND f.audio_file_name = ? AND e.file_extension = ?

SELECT content AS audio_stream FROM n2srp.audio_file f
  JOIN n2srp.audio_file_version v USING (audio_file_id)
  JOIN n2srp.language l USING (language_id)
  JOIN n2srp.audio_file_encoding e USING (audio_file_encoding_id)
  JOIN n2srp.audio_file_content c USING (content_md5_hash)
WHERE
  f.announcement_set_id = (SELECT announcement_set_id FROM n2srp.announcement_set WHERE type_of_set = 'active')
  AND l.language_name = ? AND f.audio_file_name = ? AND e.file_extension = ?

SET simple

The simple set is:

SELECT id, language_name, play_list FROM announcement_mapping WHERE resource_id = ?

SELECT id, audio_stream FROM file_audio WHERE language_name = ? AND file_name = ? AND suffix = ?

SELECT id, audio_stream FROM vpfile_audio WHERE language_name = ? AND vpfile_name = ? AND suffix = ?

Message Handling

The RtpApp uses the following messages:

• HEARTBEAT Messages.
• MANAGEMENT Messages (!MANAGEMENT-*-REQUEST inbound).
• RTP Messages (RTP-ESTABLISH inbound).