Jittery playback in ETTV beta 3

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Lekdevil.NL
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Jittery playback in ETTV beta 3

Post by Lekdevil.NL »

We've been running ETTV beta 3 for QuakeCon over the past week, and on the whole, it is performing very well. However, the viewers are experiencing some very noticeable jitter when connected to a broadcast server. Instead of seeing smooth movement and effects, everything kinda lurches ahead, interspersed with micropauses, depending on the amount of activity going on in the game at that time.

When looking at the lagometer, I'm seeing that the client is interpolating and extrapolating alternately. The more events are taking place in-game, the more extrapolation is taking place. It feels like being connected to a game server that is starved of CPU cycles, but checking "top" output shows that this is definitely not the case. The effect occurs on broadcast servers that are empty and full alike.

Is this a known bug/feature? Anything a viewer or admin can do about this at this time (I already tried spectating with high cl_timenudge values, but that didn't seem to have any effect)?

Thanks!
Last edited by Lekdevil.NL on Fri Jun 24, 2005 12:37 pm, edited 1 time in total.
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arni
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Post by arni »

<comment type='stupid'>
Thats because you didnt want the euro's to broadcast qcon games ;-)
</comment>
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Lekdevil.NL
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Post by Lekdevil.NL »

That comment is not stupid, it is false.

Anyhow, the jitter occurs irrespective of the latency between the client and the broadcast server, because it is also evident when running a broadcast server on my local PC which is connected to our hub. It might very well be dependent on the total latency between the hub playing back the demo, via the broadcast server, to the client, but I'm obviously unable to easily test that hypothesis.

In any case, playing back the demo files on a local server does not result in any jitter, so total latency might indeed be a determining factor.

For reference, here's the full broadcast chain we're using:

MASTER --> HUB (SLAVE) --> time-delay demo file --> HUB (BROADCAST) --> BROADCAST SLAVE --> CLIENT

The hub-slave and hub-broadcast servers are running on the same physical system.
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arni
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Post by arni »

we euro's had the same scenario set up some weeks ago

while some had absolutely no problem with it (me) some others complained about "lag" - dont know what type of lag or whatsoever.

But:

What i can tell you, that i think i know the type of lag you are describing - it occurs if any of the servers in the servers in the chain runs out of CPU (or other resources) (You might also want to look at the network buffers as described in the doc - Large hubs create lots of traffic)
--> I experienced this when i tried out how many slots my box can take and went to far.

About q-con broadcasts:

From what I had heard from two of your ETTV admins you did not want us to connect because euro's did not allow you to connect to rtcw nations cup or something. - Thats simply the info your admins gave out.
BTW: Should you ever want to broadcast any EU games in future, come to http://ettv.org and apply for a server slot ;-)
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Lekdevil.NL
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Post by Lekdevil.NL »

The buffers are okay: I'm getting no NET_SendPacket ERRORs. And as I said in my first post: the jitter happens even with just one viewer connected and CPU load is low (<15%).

As to your broadcast comments: I have no idea what you're talking about. Why would I want to broadcast the Nations Cup using our QuakeCon systems, or any other match for that matter? As you may have noticed, we are running a little tourney ourselves at the moment, requiring all the resources we've got. Also, QuakeCon does not have two ETTV admins.
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bani
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Post by bani »

known problem with live slaves (vs demo playback). due to latency/clock slip between the master and slave. if you connect directly to the master you shouldn't notice any jitter.

it's being worked on.
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