Re: [Ant-phone-devel] Latency, fragments and their sizes.

[Roland Stigge]

Hi Bruno,

thanks for your thorough feedback. As you probably read, some others
tried before and all your ideas are appreciated. I'm collecting them and
they are on the TODO list.

On Sat, 2004-02-14 at 12:15, Bruno Hertz wrote:
> Anyway, I'm still not sure what causes the latencies. Changing
> the fragment sizes and/or number didn't have a noticable
> effect, and I suspect they might have other reasons too.

As I proposed.

> One observation from last evening: I had a 1.5 hour
> conversation with my brother, and right from the start
> I heard my voice echoing with about 0.5 sec delay.
> Interestingly, the time I heard the echo was exactly
> (about?) the time my voice arrived at the other end.
> I verified this by alternately counting numbers with
> my brother :)

Good idea. A while back someone asked for a delay measuring protocol.
Here it is. :-)

> Moreover, the echo delay (and hence the latency) increased
> over time up to some 2 seconds. Plus, after about 40
> minutes, my brother started to hear his voice echoing too,
> corresponding to a latency resp. delay on his side. I.e.
> towards the end of the phone call his voice too reached me
> with about 2 sec delay.

This is also a known problem. We will need a better dynamic speed drift
compensation. The ISDN and dsp devices don't run in sync.

> I noticed that the (local and remote) voice
> input handling is done via Gtk callbacks, so I guess
> this rather critical and desirably realtime component
> of your app heavily relies on Gtk properly handling it?
> If so, maybe there's a source for trouble?

You are right. Since currently everything is dispatched from one thread
(which also serves the GUI), the realtime performance is bad. This
should be easily fixed by creating a POSIX thread for the ISDN/DSP
mediator (mediator.c etc.).

This might also be the reason for your experiences with xscreensaver
etc.

> Another issue: at one point during yesterday's call I mixed
> my xawtv sound into the conversation. I tried that
> before when calling myself and it worked OK, but yesterday
> I got heavy acoustic feedback and I don't know why. It
> most likely was not a local headphone <-> microphone
> feedback.

I have no idea about this. Maybe this one is not related to ANT?

> OK, sorry for the long posting

I thank you for it.

> e.g. what is that 'switchboard' you
> use for debugging and mentioned in another posting?

In German, we call it "Telefonanlage". :-) I bought it especially to
develop ANT... But maybe you already have one. Else, debugging sessions
become expensive here. After one month it was worth the investment. :)

bye,
  Roland

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