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Poorer voice quality

fotobits
Rising Star
Posts: 584
Fixes: 1
Registered: 23-06-2007

Poorer voice quality

I have enjoyed a reliable VoIP connection since Gradwell became the supplier, however, more recently I feel that the voice quality has deteriorated.  Originally, my VoIP was a better quality than my landline, now it's the reverse.
The "Test VoIP" generally shows a good connection, but I seem to experience flakey speech, both ways.
Has anyone else noticed a deterioration over the last few weeks?
Regards
21 REPLIES
glloyd
Rising Star
Posts: 1,652
Thanks: 20
Fixes: 1
Registered: 06-04-2007

Re: Poorer voice quality

Yes the audio is choppy on some calls more than others but not as good as it was and not as good as Sipgate.
fotobits
Rising Star
Posts: 584
Fixes: 1
Registered: 23-06-2007

Re: Poorer voice quality

Many thank, glloyd.  It's relevant to have confirmation at which end lies the problem!
Community Veteran
Posts: 6,249
Thanks: 428
Fixes: 39
Registered: 30-07-2007

Re: Poorer voice quality

Can't say that I've noticed any problems...
pd
Grafter
Posts: 235
Registered: 09-05-2008

Re: Poorer voice quality

I use it several times a day and don't see (hear) any problems.  Are you sure one side of the conversation is not into some heavy downloads or such like?

Peter
fotobits
Rising Star
Posts: 584
Fixes: 1
Registered: 23-06-2007

Re: Poorer voice quality

Thanks, Peter and MisterW, I'll monitor my calls more closely.
Peter, I know heavy downloading by one party seems to cause problems, however, my calls are currently only to landline numbers and unless the other party's splitter is faulty, I shouldn't have thought there would be an issue.
On my own PC, there's unlikely to be any downloading, anyway PlusNet prioritise VoIP downloading to my PC and I prioritise VoIP to the PlusNet server.
The 106-test's incoming voice is very clear, my returned voice, less so.  Is there a clue there?
Interesting that George (glloyd) has the same problem.  I wonder what our systems have in common?
I use a Zyxel P660H-D1 router and Zyxel P2002L adapter, if it's relevant.
Regards.....Noel
puddy
Grafter
Posts: 1,571
Registered: 10-06-2007

Re: Poorer voice quality

I use (like misterw) a Siemens ip dect phone and there’s no loss of quality between BT calls and VOIP calls, but I live across the road from my BT exchange and sync is 8128.
Perhaps if your further away from you exchange could be reason why the call quality suffering
Puddy
fotobits
Rising Star
Posts: 584
Fixes: 1
Registered: 23-06-2007

Re: Poorer voice quality

Many thanks Puddy, however, I don't see why bandwidth comes into VoIP quality.
I have set up my router to allocate the highest priority to Voip for the router-to-WAN direction and 100kbps of bandwidth.  G711 requires something like 84kbps, I think.
Similarly, in the receiving direction, PlusNet give highest priority to their VoIP transmissions.
I'd have thought, whatever else is being transferred, VoIP will win!
I wonder if my adsl BT-installed faceplate is unreliable?  I've had it for several years and it has seemed OK.  Would disconnecting my telephone connection to the landline side be a valid test?  I guess it would.  Perhaps I can try this during a call and see what happens.
My cordless home 'phones are connected via a base unit to both the 'phone adapter (for VoIP) and the landline (for +Net's Home Phone).  Outgoing calls default to VoIP, or by selecting a code at the handset the call is via landline.  However, I don't think this can be really relevant.
I am very grateful for your interest.
Regards.....Noel
Community Veteran
Posts: 6,249
Thanks: 428
Fixes: 39
Registered: 30-07-2007

Re: Poorer voice quality

fotobits,
You're correct in that, in principle, bandwidth shouldnt be an issue as your are only talking about, as you say , 80->100kbps.
However there are other factors which come into play for voip. A dsl line with a high error count will cause delays and affect voip quality, likewise any exchange contention will cause problems ( and no amount of prioritorisation will get round that ).
Like Puddy I have a pretty good DSL line , synchs at 8128k with a reasonably low error count < 600/day.
Check your synch speed and errors counts on your router, it could just be that the cold weather is affecting the line a little. Also check your exchange for contention using the exchange checker.

fotobits
Rising Star
Posts: 584
Fixes: 1
Registered: 23-06-2007

Re: Poorer voice quality

Many thanks, MisterW.  I synch at a constant 8128/448kbps.
I'm not sure how to obtain the error count.  There appears to be no congestion on my Exchange.
I guess I'll have to be-friend an engineer who can check my line and performance!
If I come up with anything, I'll record it on this string.
Regards.....Noel
Community Veteran
Posts: 6,249
Thanks: 428
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Registered: 30-07-2007

Re: Poorer voice quality

Have a look at the Kitz website regarding router stats http://www.kitz.co.uk/adsl/linestats_explanation.htm
and here http://www.kitz.co.uk/adsl/frogstats.php to see how to get them for various routers.
Looks like you might need to telnet into the 660 to get the error counts...
fotobits
Rising Star
Posts: 584
Fixes: 1
Registered: 23-06-2007

Re: Poorer voice quality

MisterW these are the easy-to-copy stats from my Router.  Others seem to indicate no errors :-
noise margin upstream: 24 db
output power downstream: 19 db
attenuation upstream: 13 db
noise margin downstream: 11 db
output power upstream: 12 db
attenuation downstream: 27 db
I've always thought the above were OK, referring to Kitz data, except perhaps Output Power down, 'though Im not sure as to the full meaning of these stats.
Regards....Noel
puddy
Grafter
Posts: 1,571
Registered: 10-06-2007

Re: Poorer voice quality

While you change your BT master socket get a BTi-plate (not the cheap and cheerful clones) and fit it at the same time?
This is my info for the last 7 days as you can see the errors below are very low not bad for a speedtouch 716wl  router that cost £1.98 its wireless 4 ports 2 voip plugs and adsl 2+
DSL Connection 
Link Information
Uptime: 7 days, 20:45:18
Modulation: G.992.1 Annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 / 8,128
Data Transferred (Sent/Received) [MB/GB]: 671.85 / 8.75
Output Power (Up/Down) [dBm]: 11.5 / 9.5
Line Attenuation (Up/Down) [dB]: 4.0 / 3.0
SN Margin (Up/Down) [dB]: 20.0 / 13.5
Vendor ID (Local/Remote): TMMB / ALCB
Loss of Framing (Local/Remote): 0 / 0 
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 27 / 0
FEC Errors (Up/Down): 0 / 0
CRC Errors (Up/Down): 6 / 27
HEC Errors (Up/Down): 6 / 14

lets us know how you get on
Regards
Puddy

Community Veteran
Posts: 6,249
Thanks: 428
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Registered: 30-07-2007

Re: Poorer voice quality

The critical ones are usually :-
Quote
noise margin downstream: 11 db
attenuation downstream: 27 db

You're right , those are pretty good stats. Given that you're synching at 8128k, then with a noise margin of 11db you really shouldn't be getting that many errors unless you have intermittent noise bursts on the line.
For comparison my stats are attenuation 29db with a noise margin of 8db. Typically that gives me ~ 600 corrected errors/day but I have seen occasional bursts of ~ 20/sec especially in cold/wet weather.output power upstream: 12 db
I've not had much experience with Traffic Management on domestic routers but I'd be inclined to try turning it off and seeing if there is any difference. Really, with your synch speed, bandwidth shouldn't be a problem.
Hope that helps 
fotobits
Rising Star
Posts: 584
Fixes: 1
Registered: 23-06-2007

Re: Poorer voice quality

Many thanks, MisterW.  I'm very grateful for your comments and I'll turn off the Bandwidth Management feature and, as you say, see what happens!
On reflection, I think Bandwidth Management does add further confusion to my rather hit-and-miss attempts to improve VoIP quality!
I have Voice Compression set in my adapter to 711>729.  I think that PlusNet uses G711, however, would setting the lower G729 improve things....on the basis that (as I understand it) G729 is more forgiving of errors?  Or am I rambling?
Puddy, thank you so much for sharing your stats with me.  Unfortunately, I can't really understand this information, let alone what to do about any value which might not be acceptable!  Sorry, most grateful for your trouble!
My present interface with the incoming adsl line is via a BT-installed face-plate splitter adsl v10, which, according to the BT site, cannot be fitted with the BT i-plate.  If you think the i-plate would eliminate possible interference, how should I proceed?
Thank you both and regards....Noel