[Freeswitch-users] OPUS Codec

[Colin Morelli]

Raul, I'm sure the OP was referring to 30% packet loss with FEC, which opus
can turn back into a usable audio stream. You'll absolutely notice
artifacts in the audio, and you'd clearly identify something is wrong, but
it's a heck of a lot better than 30% packet loss without FEC.

Colton,

Freeswitch supports opus, yes. I'd be curious to know why you want to
transcode between opus and G.711, unless your endpoints don't support G.711
though. Yes, FEC can help you with packet loss on one end, but if your
packet loss is on the G.711 end, then you're SOL anyway, so it seems
pointless to do this unless you can use opus all the way though.

As to how it will sound if doing the conversion, well, you're transcoding
from one lossy codec to another lossy codec. The end result will be audio
that will not sound as good as if it were just encoded in G.711 to begin
with. Remember, the nature of lossy codecs is that they're, well, lossy.
You can't make a G.711 stream sound better by re-encoding it to opus. Once
it's encoded in G.711, that information is lost.

As for CPU usage, opus is not particularly cheap. Transcoding + resampling
(if required), will considerably limit the number of concurrent calls your
FS instance can handle. Actual results are going to depend on a number of
factors that make it infeasible to talk about it. But again, you probably
don't want to be transcoding between these two codecs unless you absolutely
have two (i.e. you can't get the two endpoints to otherwise agree on a
codec). You're not going to gain any real advantage from doing this.

Best,
Colin

On Mon, May 1, 2017 at 3:54 PM, Raúl Alexis Betancor Santana <
rbetancor at gmail.com> wrote:

> 30% of packet loss ... are you mad? ... there is no way any codec could
> recover from that. Most of codecs, you will notice whenever you have more
> than 1-3% packet loss ... 30% ? ... really? ... should sound like and old
> synthetizer
>
> 2017-05-01 20:03 GMT+01:00 Colton Conor <colton.conor at gmail.com>:
>
>> Does freeswitch support transcoding from OPUS to G711? How well does this
>> work in theory? Having full HD come in via OPUS from the phone, and then
>> transcoding to crappy G711. Does it sound funny?
>>
>> We are thinking that OPUS has superior audio quality, and can withstand
>> up to 30 percent packet loss without any audio distorition. However, I
>> would say the majority of our users calls as still to the PSTN which only
>> speaks G711.
>>
>> How much processing power would it take to transcode from OPUS to G711?
>>
>> How well is the OPUS codec implemented on newer IP phones?
>>
>> I hear the Yealink supports OPUS with their new S line of phones, but I
>> also heard they pulled support for it?
>>
>> Polycom seems to only support it on the VVX 500 and VVX 600, but you have
>> to disable video according to the 5.4 release notes. OPUS must be processor
>> intensive I assume if it can't run OPUS and video at the same time. Have
>> any idea if the newer VVX, like the 411, 501, and 601 have this same
>> limitation? I know they have faster processors and ram.
>>
>>
>>
>>
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