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Bug #3807

closed

short HRv1 RTP payload on PHY based BTS implementations

Added by dexter about 5 years ago. Updated about 5 years ago.

Status:
Resolved
Priority:
Normal
Assignee:
Category:
-
Target version:
-
Start date:
02/19/2019
Due date:
% Done:

100%

Spec Reference:

Description

The RTP payload that is emitted by phy based BTSs (verified with osmo-bts-oc2g and osmo-bts-sysmo) seems to be one byte shorter (14/70 instead of 15/71 bytes) than the payload that osmo-bts-trx emits. Attached one finds two traces, one from osmo-bts-trx and one from osmo-bts-oc2g.

3GPP TS 26.103 Table 7.1.1 references IETF RFC 5993 as specification for the GSM-HR RTP audio ("Useful if an A-interface over IP is attached. or TFO is used") In 5993 one can find in chapter 5.2. Payload Structure that there is a ToC (table of contents) byte specified that is to be attached in front of the actual payload.

The problem is known since the end of 2015 since there is a branch sylvain/32c3_codec in openbsc.git that suggests a fix. According to the proposed fix there is also some mangling of the payload involved as well.


Files


Checklist

  • implement conversion function in osmo-mgw
  • add ttcn-3 test for conversion function in osmo-mgw
  • implement conversion function in osmo-bts, with VTY command to enable/disable

Related issues

Related to OsmoBSC - Bug #4002: AMR defaults to bandwidth-efficient modeResolvedlaforge05/15/2019

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