Hello list, I noticed that in an opus call where the a-leg sends usedtx=0, it is properly forwarded to the b-leg, which in this case also correctly responds with usedtx=0. However, the local SDP for the a-leg then does not have usedtx in the fmtp at all, and it seems to be enabled. My C skills are limited, but could this be a bug: static opus_codec_settings_t default_codec_settings = { .... /*.usedtx */ 1, .... }; By default, usedtx is enabled, correct? However, in static char *gen_fmtp(opus_codec_settings_t *settings, switch_memory_pool_t *pool) there's this: if (settings->usedtx) { snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf), "usedtx=1; "); } Am I interpreting this correctly that if usedtx is zero, it is omitted in the fmtp line, but then enabled, because that's the default setting? Problem is that Chrome can't handle DTX and generates comfort noise every time it kicks in. Cheers! Thomas P.S.: If my interpretation is correct, it'll also affect useinbandfec.