Question about output-mixed-per-media

[Mikhail Kalashnikov]

Hello

I tried to enable output-mixed-per-media option but it causes errors "[core] Failed to add frame to mixer: received samples for old re-used input channel" and as a result a file contains only one channel audio.

I tested it on mr13.3.1.4
rtpengine-recording config:
- output-mixed = true
- output-single = false
- output-mixed-per-media = true
- mix-method = channels
- mix-num-inputs = 4

Simple call with 2 streams, no SSRC switching.

As I can see this error "received samples for old re-used input channel" occurs because in mix_get_index next is set to media_sdp_id (https://github.com/sipwise/rtpengine/blob/master/recording-daemon/mix.c#L105) but media_sdp_id always equals 0 for both sides offer/answer (https://github.com/sipwise/rtpengine/blob/master/daemon/sdp.c#L1245).

As I can see you have an open issue about this problem https://github.com/sipwise/rtpengine/issues/1892

Could you please clarify how this option output-mixed-per-media should be used? Does it work only in some specific cases or specific configuration?

Thank you in advance

[Richard Fuchs]

On 10/08/2025 16.21, Mikhail Kalashnikov wrote:
> Could you please clarify how this option output-mixed-per-media should
> be used? Does it work only in some specific cases or specific
> configuration?

This is contributed code (see
https://github.com/sipwise/rtpengine/pull/1808) so it would be best to
ask the author.

From a quick look through the code I think it might be valid for
SIPREC-type scenarios only, i.e. media appearing only on one side of the
"call."

Cheers