Re: [Linphone-developers] Echo and stuttering on Sony Xperia Z2 tablet

[Balder Mørk]

Follow-up info: It seems that the echo problem is much less for the 
person initiating the call. The person answering the call will hear 
fragments of his own voice frequently, and I think this is when the 
other party will hear a gap in the audio.

I've also tried with a Samsung SM-P900 (NotePRO) tablet, with much 
better results. The person initiating the call will still hear his own 
voice a lot (this time not only broken fragments, but entire words and 
sentences), but there's much less stutter and bleeping noise. I've 
noticed a difference in the debug output.

Samsung SM-P900 states the following:
Setting up AudioRecord  source=7,rate=48000,framecount=24576
AudioRecord.getAudioSessionId() returned 95
AcousticEchoCanceler successfully created.
AcousticEchoCanceler enabled: 1
AcousticEchoCanceler already enabled

..while Sony SGP511 states:
Setting up AudioRecord  source=7,rate=16000,framecount=8192
AudioRecord.getAudioSessionId() returned 1159
AcousticEchoCanceler successfully created.
AcousticEchoCanceler enabled: 0
AcousticEchoCanceler enabled

I don't know if this is important, but it does look relevant. Both the 
sampling rate and different state of AcousticEchoCanceler surprise me.


regards,
Balder Mørk

Den 27.11.2014 09:38, skrev Balder Mørk:
> Hi,
> Both linphone and my app using liblinphone suffer from echo and 
> stuttering when using the built-in mic and speakers in the Sony Z2 
> tablet. I'm using two identical tablets running the same version of 
> linphone/liblinphone, and Android 4.4.4. My own app uses liblinphone 
> 2.3.2. I've tried enabling echo limiting and echo canceling, none of 
> them, or just one of them. None of the four combinations solve the 
> problem. The stutter seems to happen when the other party hears his 
> own voice for a fraction of a second, so I'm guessing that's the echo 
> limiter trying to eliminate feedback. Are there any good tips or 
> step-by-step guides to eliminating such problems for tablets?
>
> Here are some relevant lines from liblinphone startup.
>
> Native android sound support available.
> This device (Sony/SGP511/msm8974) declares it has a built-in echo 
> canceller.
> No AEC information available for model [Sony/SGP511], trying with 
> platform name [msm8974].
> Found AEC information for [Sony/SGP511/msm8974] from internal table
> Sound device information for [Sony/SGP511/msm8974] is: builtin=[yes], 
> delay=[0] ms
> Could not set voip=on: err=-38.
> Hardware output sampling rate is 48000
> Hardware is known to have bugs at default sampling rate, using 16000 
> Hz instead.
> Minimal AudioRecord buf frame size at 16000 Hz is 2048
> Could not set voip=off: err=-38.
> Card 'libmedia: android sound card' added
> SDK version [19] detected
> This device (Sony/SGP511/msm8974) declares it has a built-in echo 
> canceller.
> No AEC information available for model [Sony/SGP511], trying with 
> platform name [msm8974].
> Found AEC information for [Sony/SGP511/msm8974] from internal table
> Sound device information for [Sony/SGP511/msm8974] is: builtin=[yes], 
> delay=[0] ms
> Card 'ANDROID SND (deprecated): Android Sound card' added
>
> To me, it looks like the tablet has a built-in echo canceller, yet 
> Hacks.hasBuiltInEchoCanceller() returns false. 
> LinphoneCore.needsEchoCalibration() also returns false though, so I'm 
> not quite sure what to make of this.
>
> Also, LinphoneCall.isEchoCancellationEnabled() seems to ignore 
> whatever I pass to LinphoneCall.enableEchoCancellation() during a 
> call. It looks like I need to use the method in LinphoneCore to change 
> the value.
>
> I'm grateful for any tips or guides to solve my problem. Let me know 
> if I should provide more information.
>
>
> regards,
> Balder Mørk
>
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