hi All,

I wanted to share some testing I've done with my nokia n900 and /etc/skyhost/skypeaudiocodecs.conf config. I have this phone only for few weeks, but I do work with linux everyday.

I had lots of issues with choppy audio, but only for my end of the conversation. So after googling around and playing with several files I've had some success with this setup.

This setup I've found originally:
=============================

[G729]
payload-type=18
frequency=8000
channels=1
packet-sizes=20,30,40
default-packet-size=40
min-bitrate=8000
max-bitrate=8000

[PCMA]
payload-type=8
frequency=8000
channels=1
packet-sizes=20,30,40
default-packet-size=40
min-bitrate=64000
max-bitrate=64000

[PCMU]
payload-type=0
frequency=8000
channels=1
packet-sizes=20,30,40
default-packet-size=40
min-bitrate=64000
max-bitrate=64000

====================================

I've started with doubling bitrates from 64000 to 12800 and I had couple of very good test calls to skype echo123 testing number.

I've also tweaked frequency, but this had no affect. I did at least 10-20 calls before doing any sort of conclusions.

I noticed that calls over 3G network were better then calls over WIFI... This gave me idea that high quality codecs do not perform well and I decided to change around payloads so originally I had 18, 8, 0 and switched it to 0, 8, 18 (swapped g729 for pcmu). After doing lots of test calls I noticed huge improvement in overall quality.

I think sound quality has dropped to g729 level, but choppiness was gone. After experimenting further with payloads I had some really crisp and clean calls on other codecs too.

Originally I had choppy gaps at random times and after changing bitrates and payloads I noticed that I have choppy gaps in the first few seconds but later call quality is good.

I think phone must be trying to figure out which codec to use during the call and this is a problem.

Please share your experiences here, so we all know what works... I have a feeling different bitrates+codecs is key to getting skype call quality right.

After doing changes on the conf file you do not need to restart your phone - just dial skype call and test the quality. Make a backup first - if you modify it too much your skype will not work.

My current set-up:

=============================

[G729]
payload-type=0
frequency=8000
channels=1
packet-sizes=20,30,40
default-packet-size=40
min-bitrate=8000
max-bitrate=8000

[PCMA]
payload-type=8
frequency=8000
channels=1
packet-sizes=20,30,40
default-packet-size=40
min-bitrate=64000
max-bitrate=64000

[PCMU]
payload-type=18
frequency=8000
channels=1
packet-sizes=20,30,40
default-packet-size=40
min-bitrate=64000
max-bitrate=64000


====================================

UPDATE: this method only works for some phones. On the latest kernels/power kernels this doesn't work.

Made a 30 minute call to my brother in Australia from USA using wifi and these settings. Was crystal clear and no chop.

Take from that what you will.

did you previously have issues with skype on such calls?

Some - main problem was not so much call quality as chop. I didn't notice any chop in the 30 minutes or so.

I have the impression that using earphones works much better than using the phone directly.
Maybe the sound suppression system is the problem? In that case, I don't really know what could be done about it.

ATLAST! someone noticed!!!

BAD QUALITY on skype! but this tweak is doing good. anymore tweaks?

All these things wrong. I've tried once again to figure out influence any changes in file skypeaudiocodecs.conf. I've done 'cat /dev/random >skypeaudiocodecs.conf'. As you know its file got binary. After that I killed all skyhost processes. And do you know? It works as nothing has happened.

It seems to me there is only way to communicate with skype company or developers. There is no another way!

guys , more bitrate means more data need to be sent , lower it

Your assumption is incorrect, but your results are correct:

skypeaudiocodecs.conf is set of optional settings - these settings are used if they are available - if file is missing it will default to default settings. Try corrupting the file and you will see effects

This is true... But my guess is that problems with choppiness are caused by the payload - software is optimizing the quality by switching codecs. This is great on paper, but nobody bother to check if this works. Well it used to work, but now it doesn't. It is a shame really.

I'm a programmer and I'm embarrassed for the guys who did this work. After upgrading to the newer kernels - I got so many issues that I cannot use Skype at all.

Back to the topic - increasing bitrate strangely helps in a way... As soon as I get CPU more stable Skype quality is much better. But this is all very temperamental - fixes do work for few days till some other patch or update breaks this balance.