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Re: [Linphone-users] Windows Call Quality Window vs iPhones - Further Te

From: Robert Dixon
Subject: Re: [Linphone-users] Windows Call Quality Window vs iPhones - Further Testing
Date: Sat, 24 Oct 2015 18:10:07 -0400

OPUS works much better! See below.

On Oct 24, 2015, at 4:56 PM, Russell Treleaven <address@hidden> wrote:

On Sat, Oct 24, 2015 at 4:02 PM, Robert Dixon <address@hidden> wrote:
Thanks for your reply!

On Oct 24, 2015, at 2:40 PM, Russell Treleaven <address@hidden> wrote:

What version of ios?
7.1.2  That is the latest version available for the Iphone 4.

I thought we were talking about the iPhone4s for which the latest version is 9.1
What version of linphone?
What codec are you using?
Whatever is the default.  Should I try something else?

Yes codec selection makes a big difference.
Opus is likely your best choice for a number of reasons.

Can you be more specific about the sound quality issues?
The transmitted sound is fine for the first 10 or 15 seconds.  Then it begins to get choppy, and the call quality indicator on the PC or Mac
begins to say things like “very bad”.  The delay time to the other end gets greater and greater, up to 5 or 10 seconds.
After that it is unintelligible at the other end.

This is unique to the Iphone 4 s.  The Iphone 5 s work fine, but they have IOS 9.1 .


Is there a b2bua or media proxy between the endpoints?

No.  Both endpoints connect only to a wifi access point and thence to each other.

"choppy" audio on the pc means lost or late packets at uac or along the way.
The delay time is increasing because the uas is growing it's jitter buffer to packet loss/delay.

I would suggest you do a-b testing with ping or similar to see if the problem is in the network stack of the the older iPhone.

Also have a look at this

opus will take more processing power but the overall quality is far beyond toll quality and the packet loss concealment and forward error correction make it excellent for dodgy networks.

If I enable the opus audio codec and turn off all others on the Iphone4, the audio problems are completely solved. Even if sometimes the connection quality meter goes down, the audio still remains OK.  I have to set the audio codec bitrate to 20 kbits/sec for best results.
Voice Processing is turned on by default. Should that be left on?

If the loss is cpu can't keep up, then you probably wan't a codec with lower cpu demands like pcmu, pcma or gsm.

I could try those.

But  if I try video, there are problems.  (Maybe this is expecting too much.)
The video takes a long time to do anything, (30 seconds) and finally a still picture appears.  It changes to a new frame maybe every
15 seconds.  The audio remains good. But sometimes the video suddenly becomes very good but then the audio stops completely.

On the Iphone5, audio and video work fine.

This is already a huge overall improvement!   I am hoping you can provide additional suggestions to improve the video.


If the loss is due to the network stack or the network itself, then you probably wan't a codec with packet loss concealment technology and forward error corrections like opus.

Since you say about codecs "Whatever is the default.  Should I try something else?" Maybe you should consider getting some help with the VoIP part of your project.


Russell Treleaven

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