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.