[Freeswitch-users] OPUS Codec

Wed May 10 19:35:46 MSD 2017

Better check with "opus_debug on"  on the FS CLI. Eg:
2017-05-10 16:28:05.724001 [DEBUG] mod_opus.c:453 decode: opus_frames [1]
samples [960] audio bandwidth [WIDEBAND] bytes [75] FEC[yes] channels[1]
Look at the audio bandwidth of the decoded packets . If the audio bandwitdh
is WIDEBAND, then the sample rate is 16 khz.
You cannot find this out by looking at the pcap , the RTP timestamp is
incremented as described by the SDP profile , so always at 48 khz (which is
960 for 20 ms ptime ) .

Cheers,
Dragos

On Wed, May 10, 2017 at 2:38 PM, Colton Conor <colton.conor at gmail.com>
wrote:

> Anyone know on Polycom VVX's using OPUS, what is the sample rate? 8Khz or
> 48Khz or somewhere inbetween?
>
> I looked a at call through VoIP Monitor, and it said OPUS48 as the codec.
> Buy since "the OPUS
> specification says that the SDP must always specify 48 kHz and 2 channels"
> according to Kristian Kielhofner", I assume it just sadys OPUS 48 because
> of this.
>
> Like I mentioned, I though that G.722 between two Polycom's sounded better
> than OPUS to my suprise. I assume this is because G.722 is at 16 kHZ, and
> Polycom's opus is potentially at 8kHZ.
> The softswitch we are using (Netsapiens) does not do any trasconding to my
> knowledge, so the payload has to be whatever Polycom encodes/decodes at.
>
> Is there a way to tell what kHz the Opus codec is running at on a Polcom
> VVX, or by looked at a packet capture?
>
>
> On Sat, May 6, 2017 at 1:26 PM, Kristian Kielhofner <kris at kriskinc.com>
> wrote:
>
>> FreeSWITCH can limit Opus to a configured sample rate but the OPUS
>> specification says that the SDP must always specify 48 kHz and 2
>> channels.
>>
>> OPUS is a combination of SILK and CELT, with the original PLC+FEC
>> coming from SILK. There are effectively three modes in OPUS - SILK,
>> CELT, and hybrid. It's not clear to me how well PLC+FEC works in the
>> hybrid and CELT modes used at higher sample rates. I haven't looked at
>> it specifically (or tested it) but my suspicion is that PLC+FEC works
>> much better the closer you get to "pure" SILK mode, which is
>> essentially what limiting the sample rate to 8 kHz does.
>>
>> On Sat, May 6, 2017 at 10:21 AM, Colin Morelli <colin.morelli at gmail.com>
>> wrote:
>> > 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
>> >>> brian at freeswitch.org
>> >>>
>> >>> Twitter: @FreeSWITCH , @briankwest
>> >>>
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>> >>
>> >>
>> >> ____________________________________________________________
>> _____________
>> >> Professional FreeSWITCH Consulting Services:
>> >> consulting at freeswitch.org
>> >> http://www.freeswitchsolutions.com
>> >>
>> >> Official FreeSWITCH Sites
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>> >> http://www.cluecon.com
>> >>
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>> >
>> >
>> > ____________________________________________________________
>> _____________
>> > Professional FreeSWITCH Consulting Services:
>> > consulting at freeswitch.org
>> > http://www.freeswitchsolutions.com
>> >
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>>
>>
>> --
>> Kristian Kielhofner
>>
>> _________________________________________________________________________
>> Professional FreeSWITCH Consulting Services:
>> consulting at freeswitch.org
>> http://www.freeswitchsolutions.com
>>
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>
>
> _________________________________________________________________________
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>
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