Stripping unsupported codec X-NSE due to active transcoding

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Matthew H

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Jun 22, 2026, 9:25:05 AM (7 days ago) Jun 22
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Hi,

I am using rtpengine with kamailio 6.X and one of the endpoints uses the NSE-X codec. I'd like it to transparently pass through rtpengine whilst still offering transcoding for the other codecs, however I get the following error:

Stripping unsupported codec X-NSE due to active transcoding

Here's the kamailio command:

                KSR.rtpengine.rtpengine_manage("SIP-source-address replace-origin codec-mask=G729 codec-transcode=G722 codec-transcode=PCMA codec-transcode=PCMU codec-transcode=GSM codec-transcode=telephone-event")

and the logs filtered for occurrences of X-NSE: 

[1782134497.830245] DEBUG: [21E783EA-6D7411F1...@10.26.10.70]: [codec] Adding codec X-NSE/8000/192-194 (100)
[1782134497.830281] DEBUG: [21E783EA-6D7411F1...@10.26.10.70]: [codec] Adding codec X-NSE/8000/192-194 (100)
[1782134497.830451] DEBUG: [21E783EA-6D7411F1...@10.26.10.70]: [codec] Checking receiver codec X-NSE/8000/1/192-194 (100)
[1782134497.830457] DEBUG: [21E783EA-6D7411F1...@10.26.10.70]: [codec] Creating codec handler for X-NSE/8000/192-194 (100)
[1782134497.830464] DEBUG: [21E783EA-6D7411F1...@10.26.10.70]: [codec] No codec support for X-NSE/8000/192-194
[1782134497.830467] DEBUG: [21E783EA-6D7411F1...@10.26.10.70]: [codec] Shutting down codec handler for X-NSE/8000/1
[1782134497.830473] DEBUG: [21E783EA-6D7411F1...@10.26.10.70]: [codec] Using passthrough handler for X-NSE/8000/192-194 (100) with DTMF -1, CN -1
[1782134497.830794] DEBUG: [21E783EA-6D7411F1...@10.26.10.70]: [codec] Stripping unsupported codec X-NSE due to active transcoding
[1782134497.830810] DEBUG: [21E783EA-6D7411F1...@10.26.10.70]: [codec] Using passthrough handler with new SSRC for X-NSE/8000/192-194
[1782134510.342672] DEBUG: [codec] Shutting down codec handler for X-NSE/8000/
1

Does anyone have any suggestions?

Thanks
Matthew

Richard Fuchs

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Jun 22, 2026, 10:39:42 AM (7 days ago) Jun 22
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What's the exact call scenario, i.e. which codecs on which side and which ones for transcoding where?

This sort of handling is/was necessary because depending on the scenario, it can be unpredictable which codecs are answers will contain and therefore which codecs must be transcoded, but with the better codec matching we have now, it may not be needed any more.

Cheers
Matthew --
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Matthew H

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Jun 22, 2026, 10:54:13 AM (7 days ago) Jun 22
to Sipwise rtpengine
Hi Richard,

For this exact scenario the "A" leg is offering G711A and X-NSE. Almost all of the "B" leg endpoints will offer/answer G711A with the exception of one "service" which is GSM only and will require transcoding.

Currently Kamailio doesn't know if a service requires transcoding in advance but we could potentially add something there, or we could put a B2BUA with transcoding support in front of GSM - but it would be nice if we could just use rtpengine as-is for this scenario.

Thanks
Matthew
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