Rather than necro an old post which seems to have similar issues (http://forums.grandstream.com/forums/index.php?topic=29580.msg87807#msg87807), we have issues with new DP750/720 devices when using Opus, but only when used in a bridge scenario.
We are using Asterisk 14.0.2 with the recently announced official Opus support. Our test environment is DP750 188.8.131.52 (upgraded from shipping firmware, same issue), Digium D40 2.2.0, Jitsi 2.8 and Android 6.0.1 native SIP stack, so a decent mix of hardware and software clients both with and without Opus support.
Opus to Opus without transcoding works perfectly - from Jitsi to GP750 and the other way.
If I force various codecs, Asterisk creates a basic bridge to transcode. I’ve forced this on various devices to see what happens. In the list below, first device is calling device and issue reports are from the perspective of the GP750.
Opus on Jitsi to g722 on D40 - works perfectly
g722 on Jitsi to g722 on DP750 - works perfectly
g722 on D40 to to Opus on Jitsi - works perfectly
g711 on Jitsi to g722 on DP750 - works perfectly
g722 on D40 to Opus on DP750 - buzzing on received audio, sent audio is audible but "distant"
g722 on Jitsi to Opus on DP750 - buzzing on received audio, sent audio is audible but "distant"
g711 on Jitsi to Opus on DP750 - buzzing on received audio, sent audio is audible but "distant"
Opus on DP750 to g722 on Jitsi - buzzing on received audio, sent audio is audible but “distant”
ERIC TAMME had a similar sounding issue in the post I referenced above but using FreeSWITCH in a bridging application, so this isn’t specific to Asterisk.
The issue is only apparent when transcoding Opus on the DP750. Transcoding any other format from the 750 (g711, g722 etc.) or doing Opus to Opus is fine and as I can transcode from Opus to anything on other devices, I can only conclude it’s an issue with the 750.
Is there any update on the bug raised by Eric? We’ve purchased these phones for their Opus ability but if we can’t transcode to another format, we can’t make calls to anything that doesn’t support Opus…
Please let me know if there’s any further information I can provide.