audio problem with GSM on Symbian

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The problem is the voice when we using the GSM-FR (full rate) codec on Nokia
71 connected on wireless network (case Rogers Canada). 

The "wav" file is a registration of my voice when I leave a message on my
voicemail at home on a PSTN phone.

We try to improve the voice quality :-).  

 

Thanks,

George.

 

  _____  

From: pjsip-bounces@xxxxxxxxxxxxxxx [mailto:pjsip-bounces at lists.pjsip.org]
On Behalf Of Benny Prijono
Sent: Tuesday, May 12, 2009 2:14 PM
To: pjsip list
Subject: Re: audio problem with GSM on Symbian

 

On Tue, May 12, 2009 at 6:57 PM, George Evi <george.evi at ctcinc.ca> wrote:

Hi Benny,

 

Thanks for your response. I have already tested in LAN and more than that on
Wi-Fi connection and it works fine.

Also I tested on wireless network (Access Point Rogers Canada) with PCMU and
we got a good voice quality.

 


I see. Sorry if I missed that info. So regarding the problem, what is the
problem again? :)
I can hear several impairments in the WAV that you sent me, but not sure
which particular problem you're referring to.

We try to use a codec with less bandwidth (low bit rate) like GSM or iLBC.
Unfortunelly our Sip service provider supports for the moments only PCMU,
GSM-FR & iLBC mode 30.

I tried last week iLBC but for some reason after SIP session when media
session starts the application blocks (may be a bug ???). I'll continue to
investigate this problem. 

 

It's probably because iLBC would take all the CPU in the handset. Talking of
which, is APS-Direct out of question? With APS-Direct the codec
encoding/decoding will be done in hardware and it also supports iLBC.



Could you tell me, how did you test client/pjsua on E70 with different
codecs?

 


For us it's easy, we use pjsua on the other side so just needed to
disable/enable codecs there.
 

When I do such tests I set the priority at a higher level then the other
codecs (e.g. for GSM) in "pjsua_media_subsys_init" (pjsua_media.c) and I
comment the section of code in function "process_m_answer" (sdp_neg.c):

 

      /* Arrange format in the offer so the order match the priority

       * in the answer

       */

//!ge5may09       for (i=0; i<answer->desc.fmt_count; ++i) {

//        unsigned j;

//        pj_str_t *fmt = &answer->desc.fmt[i];

//

//        for (j=i; j<offer->desc.fmt_count; ++j) {

//          if (pj_strcmp(fmt, &offer->desc.fmt[j])==0) {

//              str_swap(&offer->desc.fmt[i], &offer->desc.fmt[j]);

//              break;

//          }

//        }

//    }

 

, because my Voip provider sends always in this order (priority) 

 

CSeq: 7436 INVITE

User-Agent: Asterisk PBX

Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY

Supported: replaces

Contact: <sip:5145294251 at 64.34.49.82 <mailto:sip%3A5145294251 at 64.34.49.82> >

Content-Type: application/sdp

Content-Length: 307

 

v=0

o=root 2719 2719 IN IP4 64.34.49.82

s=session

c=IN IP4 64.34.49.82

t=0 0

m=audio 18934 RTP/AVP 0 3 113 101

a=rtpmap:0 PCMU/8000

a=rtpmap:3 GSM/8000

a=rtpmap:113 iLBC/8000

a=fmtp:113 mode=30

a=rtpmap:101 telephone-event/8000

a=fmtp:101 0-16

a=silenceSupp:off - - - -

a=ptime:20

a=sendrecv

 

--end msg--Incoming Response msg 183/INVITE/cseq=7436 (rdata0x71e46c) in
state ProceedingState changed from Proceeding to Proceeding,
event=RX_MSGReceived

 

, always the PCMU in 1st position. Without comments the codec manager has
all the time this order of codecs.


Yeah,  we don't support multiple/simultaneous codecs (as Asterisk indicated
in the 200/OK), so we'll just take the first one.

 

Is there another way to have the same result? 

 

What if you enable only one codec at a time in the application? According to
the spec, callee/answerer should only answer with codec(s) which are
available in the offer, so it should choose one codec in the answer too.

cheers
 Benny

 

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