Good 2-way video but audio clear only 1-way

Question

The problem is with audio during Mac-to-PC AV chats.
I'm using an iSight on a 15" PowerBook (10.3.9) with cable ISP (tested 356kbps up / 3mbps down). The PC is newer Dell running Windows XP with Quickcam Fusion and similar cable ISP performance.
The Mac and PC achieve good video and the PC receives good audio, but for some reason the Mac receives choppy, unusable audio and sometimes none at all.
We followed all of the posts to make sure correct ports are opened on both ends, that SP2 and extra component are installed on the PC, that the PC's mic records correctly, etc. Went through the tuning wizards, the full duplex settings, fiddling in/out volumes, echo cancellation, bit rates and cps, etc. -- all of the things recommended by EZJim's posts and the links therein, plus all of the ideas gleaned from Logitech and iVisit and anywhere else we could Google (but obviously we're missing something
First I tried iChat (2.1) to AIM (5.9) -- could not hear any audio at all from the PC.
Next I tried iVisit 3.4.3 -- audio was trying to get through but was heavily clipped.
Next, both parties connected to the iVisit Help Desk. The PC-PC connection was good for both audio and video. The help desk PC-Mac connection was good for video but once again the audio was too choppy to be intelligible.
I connected to the iChat user test account at appleu3test01 and achieved excellent video and the incoming audio was excellent too.
Using headphones to eliminate any potential feedback loop (even after trying with speaker volume way down) had negligible effect on Mac-PC connections.
Anyone else experience this problem? Any ideas? On the surface, the problem seems to be with how the PC sends audio or how the Mac receives it -- but I've overlooked the obvious before so...
I can give more specific details as to what we've tried. Appreciate any help!
Thanks -sailhome

Answer 1

EZ Jim -- thanks for staying with this -- I respect all the time and detail you are putting into helping.
     --- info still shows that you are using Mac OS X (10.3.6) ---
Sorry to confuse you. I'm definitely on 10.3.9. I don't post very often and hadn't updated my profile recently. (FWIW, I still have the iMac shown in the profile Anyhow, no 10.3.6 issues lurking.
     --- using wireless internet connections ---
I am using an Airport but it passes all the criteria. The Airport sits immediately behind the cable modem and the modem is not serving DHCP, only the Airport does that (no address conflicts). The Mac OS firewall is in place, but I have followed the instructions to open firewall ports per http://docs.info.apple.com/article.html?artnum=93208 -- in fact I opened all of 5060, 5190, 5297, 5298, 5353, 5678, 16384-16403 to make certain nothing gets blocked.
The computer is achieving 356kbps/3mbps wirelessly (dslreports) and has full bars in connection status. There have not been any packet error messages. The computer does not compete for bandwidth during AV sessions. I could hook the computer directly to the modem but given the high level of performance it does seem unlikely bandwidth is the problem.
     --- Connection Doctor ---
Here are three observations from recent sessions:
1) Using iChat-to-AIM the video quality stayed pegged at 100%, the frame rates hovered between 12-13fps, and the bit rates hovered at ~180kbps.
2) Using iChat-to-AIM the audio icon was dimmed, neither party heard audio and Connection Doctor showed zero audio activity. Audio simply not available. This is perplexing because previously the PC could hear my audio fine, it was just my Mac that couldn't hear their audio.
3) Using iVisit (I know you aren't familiar with it), video hovered at 25-30fps and bit rates hovered at 130-150kbps. Audio operated at a constant 32kbps (ADPCM setting). Bandwidth utilization was set to cap at 500kbps so there was plenty available had the application wanted it -- the point being that bandwidth does not appear to be a limiting factor in performance between the other party and myself.
It appears there is enough broadband speed for iChat
--- That is about all I know about "packets". You seem to know more about packets ---
Only enough to ask dangerous questions
     --- If the problem occurs only occasionally ---
I'll need to develop more AV buddies to reach a conclusion on that. My two buddy experiences with Mac-PC connection are consistent (bad audio). I'm in the process of making some Mac-based AV contacts -- would you be interested in testing a brief chat?
My Mac operates fine (no quirks), is up to date (on Panther), I do the repair permissions protocol before/after every software install, etc.
ISP connection is an interesting proposition -- but could that be the problem if video is running so smoothly both directions? I would think that if bandwidth were dodgy then video would fizzle out at least as quickly as audio (and probably faster since audio requires comparatively little bandwidth). Is there some sort of priority given to video when it comes to bandwidth utilization within the connection?
From what I have gleaned, for Mac-PC connections the only free apps that currently support full AV chats are iChat-AIM and iVisit, so doesn't appear there will be other apps to compare against unless we start spending more money.
     --- certain buddy problem ---
Checked out http://www.ralphjohnsuk.dsl.pipex.com/page15.html#CertainBuddy . That was interesting but none of matches my setup.
Maybe it's time to throw in the towel and try Skype simultaneously with one of the functioning video apps. Was hoping for simplicity but is seems we've gotten way beyond that with this one!...
Open to any more comments you (or anyone) have. Thanks again -sailhome