[Freeswitch-users] OPUS Codec

[Colin Morelli]

Transcoding != resampling. Often times you will have to do both to convert
audio streams, where transcoding is the act of converting between the two
audio codecs' data format, and resampling is changing the sampling rate of
the audio (8khz in your case).  Opus is a completely different audio codec
than G.711. Even if they're both at 8 khz, you'll have to transcode between
the two, though you may be able to avoid the cost of resampling the audio
to a different rate.

Opus can handle sampling rates from 8khz-48khz. Sampling rates make a
*huge* difference
to audio quality (they'll effectively define the range of audio frequencies
you can capture). If you're running opus at a constant 8khz, the reason
G.722 sounds better is almost certainly because it's using a 16khz sampling
rate. Most likely if you run opus at 16khz, it'll sound similar to G.722.
If you have the capacity (and the devices support it), pushing opus to
super-wideband or full band (24khz/48khz sampling rates, respectively) will
yield much better audio quality.

My guess (admittedly it's just an educated assumption), is that most WebRTC
companies are using fullband opus in VBR mode simply because this is the
default in WebRTC. Without mangling the SDP, this is what you're going to
get.

Best,
Colin

On Sat, May 6, 2017 at 10:41 AM, Colton Conor <colton.conor at gmail.com>
wrote:

> So what does today support FEC/PLC today?
>
> We tested two Polycom VVX phones with the opus codec, and overall thought
> that G.722 sounded much better than OPUS for some reason.
>
> So using Opus at 8 KHz, does that mean that there will be less or no
> transcoding to G.711 since its also in 8 KHz?
>
> What are most of the web only WebRTC companies using as far as OPUS goes?
> What bitrate and KHz?
>
> On Fri, May 5, 2017 at 8:33 AM, Brian West <brian at freeswitch.org> wrote:
>
>> None of the hardware phones do FEC/PLC last I tested, Sonus has OPUS
>> support, but again no FEC/PLC support.
>>
>> /b
>>
>>
>> On Wed, May 3, 2017 at 2:16 AM, EL <fs.user at fordior.net> wrote:
>>
>>>
>>> Yealink is supporting OPUS on several other models since firmware
>>> V81:
>>>
>>> Quote:
>>> "We will support opus on the standard V81 of
>>> SIP-T40P/T23P/T23G/T2 1(P) E2/T19(P) E2."
>>>
>>> Source: http://forum.yealink.com/forum/showthread.php?tid=29650&pid=
>>> 51262&mode=threaded
>>>
>>> I can confirm OPUS implementation on the 'T21P E2' model.
>>>
>>> --
>>> EL
>>>
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>>
>>
>>
>> --
>>
>> *Brian West*
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