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Summary:ASTERISK-29532: Issue with maxptime and VolTE (Voice Over LTE)
Reporter:Renato Ribas (ribascr)Labels:
Date Opened:2021-07-27 16:04:46Date Closed:
Priority:MinorRegression?
Status:Open/NewComponents:Codecs/General
Versions:16.19.0 Frequency of
Occurrence
Related
Issues:
Environment:Sangoma Linux release 7.8.2003 (Core)Attachments:
Description:Hello how are you?
Some telecom providers have problems with outgoing calls over the SIP trunk if destines using VoLTE (Voice Over LTE).
According to diagnosis, the value of maxptime=150, however, according to RFC 4566, it must be a multiple of 20.
The parameter is fixed in the asterisk code in codec_builtin.c, when performing the manual compilation I lose some functionality of commercial modules like Sysadmin in FreePBX.
Would it be possible in future versions for the parameter to be pre-compiled according to RFC?
Thanks
Comments:By: Asterisk Team (asteriskteam) 2021-07-27 16:04:51.354-0500

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By: Joshua C. Colp (jcolp) 2021-07-27 16:09:29.291-0500

Can you provide the language or part of the RFC which actually states this?

By: Renato Ribas (ribascr) 2021-07-27 16:18:55.435-0500

I will look for the excerpt in the RFC, as the adjustment information was requested by the telecom operator.

As a test I performed the procedure of changing the source code and replacing the binary and this really solves the problem

cd /usr/src

wget http://downloads.asterisk.org/pub/telephony/asterisk/old-releases/asterisk-16.17.0.tar.gz

tar xvf asterisk-16.17.0.tar.gz

asterisk-16.17.0 cd

cd main

vim or nano codec_biltin.c - (Change maximum_ms = 120 to ulaw, alaw and maximum_ms = 220 to g729)

./configure --libdir=/usr/lib64 --with-jansson-bundled

make menuselect (Select Macro and Sounds EN and Save)

make

fw console stop

mv /usr/sbin/asterisk /usr/sbin/asterisk_rpm

cp /usr/src/asterisk-16.17.0/main/asterisk /usr/sbin/

fw console start

Thanks

By: Renato Ribas (ribascr) 2021-07-27 16:28:40.145-0500

Updated the maxptime for better clarification.  The sentence that
     previously read: "The time SHOULD be a multiple of the frame
     size." now says "The time SHOULD be an integer multiple of the
     frame size."  This should have no impact on interoperability.

maxptime: The maximum amount of media which can be encapsulated
              in a payload packet, expressed as time in milliseconds.
              The time is calculated as the sum of the time that the
              media present in the packet represents.  The time SHOULD
              be an integer multiple of the frame size.  If this
              parameter is not present, the sender MAY encapsulate any
              number of speech frames into one RTP packet.

On the other hand, the transcoding from G.711 to UEMCLIP is not
  entirely straightforward.  Since there are no means to generate
  enhancement sub-layers, a G.711 bitstream can only be converted to
  UEMCLIP Mode 0 bitstream.  If the original G.711 bitstream is encoded
  in A-law, it should first be converted to u-law to become the core
  layer.  Because a UEMCLIP frame size is 20 ms, a u-law-encoded G.711
  bitstream MUST be a 160-sample chunk to become a core layer.

I understand by definition that the maxptime value needs to be a multiple of 20.

https://datatracker.ietf.org/doc/html/rfc4566
https://datatracker.ietf.org/doc/html/rfc5686