2006-09-20 17:39:59 +00:00
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Overview
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Asterisk currently supports configurable RTP packetization per codec for
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select RTP-based channels.
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Channels
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These channel drivers allow RTP packetization on a user/peer/friend
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or global level:
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chan_sip
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chan_skinny
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chan_h323
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chan_ooh323 (Asterisk-Addons)
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2007-04-03 22:33:03 +00:00
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chan_gtalk
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chan_jingle
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2006-09-20 17:39:59 +00:00
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Configuration
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To set a desired packetization interval on a specific codec,
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append that inteval to the allow= statement.
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Example:
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allow=ulaw:30,alaw,g729:60
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No packetization is specified in the case of alaw in this example,
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so the default of 20ms is used.
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Autoframing
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In addition, chan_sip has the ability to negotiate the desired
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framing at call establishment.
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In sip.conf if autoframing=yes is set in the global section, then
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all calls will try to set the packetization based on the remote
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endpoint's preferences. This behaviour depends on the endpoints
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ability to present the desired packetization (ptime:) in the SDP.
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If the endpoint does not include a ptime attribute, the call will
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be established with 20ms packetization.
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Autoframing can be set at the global level or on a user/peer/friend
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basis. If it is enabled at the global level, it applies to all
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users/peers/friends regardless of their prefered codec packetization.
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Codec framing options
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The following table lists the minimum and maximum values that are
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valid per codec, as well as the increment value used for each.
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Please note that the maximum values here are only recommended
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maximums, and should not exceed the RTP MTU.
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Name Min Max Default Increment
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g723 30 300 30 30
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2006-09-26 18:10:07 +00:00
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gsm 20 300 20 20
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ulaw 10 150 20 10
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alaw 10 150 20 10
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g726 10 300 20 10
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ADPCM 10 300 20 10
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2006-09-20 17:39:59 +00:00
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SLIN 10 70 20 10
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lpc10 20 20 20 20
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g729 10 230 20 10
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speex 10 60 20 10
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ilbc 30 30 30 30
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2006-09-26 18:10:07 +00:00
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g726_aal2 10 300 20 10
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2006-09-20 17:39:59 +00:00
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Invalid framing options are handled based on the following rules:
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1. If the specified framing is less than the codec's minimum, then
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the minimum value is used.
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2. If the specific framing is greater than the codec's maximum, then
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the maximum value is used
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3. If the specificed framing does not meet the increment requirement,
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the specified framing is rounded down to the closest valid
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framing options.
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example allow=ulaw:33 will set the codec to 30ms framing
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4. If no framing is specified in the allow= directive, then the
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codec default is used.
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