cl_nodelta

[ouroboro]

Sorry, I know this isn't a Q3 source code discussion forum, but I don't know of any such place and I know smart people live here, so...

Can someone translate this from C to E please?

Code: Select all

// begin a client move command
if ( cl_nodelta->integer || !cl.snap.valid || clc.demowaiting
	|| clc.serverMessageSequence != cl.snap.messageNum ) {
	MSG_WriteByte (&buf, clc_moveNoDelta);
} else {
	MSG_WriteByte (&buf, clc_move);
}

This is the only reference to cl_nodelta in the Q3 source (cl_input.c - line 748). When I set this to 1, the bottom line of my lagometer gets slightly rough, so I wondered what it does exactly. Google says it turns "delta compression" on/off, so I guess I'm asking what that actually means in English, and how it might affect play.

Danke

P.S. I must confess that this question was brought on by the raving lunacy of LilleBror and his asinine cvar checks.

[deej]

P.S. I must confess that this question was brought on by the raving lunacy of LilleBror and his asinine cvar checks.

LOL he's getting to ya .

[Spoofeh]

This is where it ends up, assuming I read it correctly: sv_snapshot.c, SV_WriteSnapshotToClient()

client->deltaMessage is -1 if cl_nodelta is 1.

Code: Select all

	// try to use a previous frame as the source for delta compressing the snapshot
	if &#40; client->deltaMessage <= 0 || client->state != CS_ACTIVE &#41; &#123;
		// client is asking for a retransmit
		oldframe = NULL;
		lastframe = 0;
	&#125; else if &#40; client->netchan.outgoingSequence - client->deltaMessage 
		>= &#40;PACKET_BACKUP - 3&#41; &#41; &#123;
		// client hasn't gotten a good message through in a long time
		Com_DPrintf &#40;"%s&#58; Delta request from out of date packet.\n", client->name&#41;;
		oldframe = NULL;
		lastframe = 0;
	&#125; else &#123;
		// we have a valid snapshot to delta from
		oldframe = &client->frames&#91; client->deltaMessage & PACKET_MASK &#93;;
		lastframe = client->netchan.outgoingSequence - client->deltaMessage;

		// the snapshot's entities may still have rolled off the buffer, though
		if &#40; oldframe->first_entity <= svs.nextSnapshotEntities - svs.numSnapshotEntities &#41; &#123;
			Com_DPrintf &#40;"%s&#58; Delta request from out of date entities.\n", client->name&#41;;
			oldframe = NULL;
			lastframe = 0;
		&#125;
	&#125;

My interpretation: cl_nodelta turns "delta compression" on/off.

[ReyalP]

SaltehLies.

It chooses whether or not the packets fly on Delta Airlines or not. Delta has decent service(for an American carrier, which doesn't say much unless you are used to Aeroflot or Sudan Air), but is a bit pricey. So you might want to use nodelta unless you have a lot of frequent flyer miles saved up, or generally have money burning a hole in your pocket. Delta compression is what you get when you fly economy class. By the time you get to your destination, you are compressed, unless you suffered from explosive decompression.

You could use cl_aeroflot instead, but then your packets would just get stuck in Sheremetyevo airport security, and never actually get anywhere.

edit:
I should add that delta compression is pretty efficient, but not quite as efficient as South West compression.

[HarryHirsch]

LOL @ ReyalP *g*

[ouroboro]

LOL WTF

ROFL @ Sudan Air.

[Nail]

toggles Delta-compression of client and server packets

[deej]

toggles Delta-compression of client and server packets

But wtf is Delta-compression?

[ouroboro]

toggles Delta-compression of client and server packets

But wtf is Delta-compression?

[Ragnar_40k]

Delta compression: You don't store the values itself, but the difference (i.e. the delta) between successive values.

Oh, and Delta declared bankruptcy in 2005 ...

[deej]

Delta compression: You don't store the values itself, but the difference (i.e. the delta) between successive values.

Sweet! Is that a good thing or a bad thing ?

[ReyalP]

Sweet! Is that a good thing or a bad thing ?

It's a good thing. The only reason to turn it off would be debugging.

[deej]

It's a good thing. The only reason to turn it off would be debugging.

So the paranoid amongst us should forbid setting cl_nodelta to 1? I wonder whether or not this can be exploited to generate lag on demand.

[ouroboro]

It's a good thing. The only reason to turn it off would be debugging.

So the paranoid amongst us should forbid setting cl_nodelta to 1? I wonder whether or not this can be exploited to generate lag on demand.

LilleBror says yes! Isn't that good enough for you?

Seriously though, if it's only use is debugging, I can't imagine why anyone would want to change it unless they were being devious - even if those devious intentions were misguided and pointless.

[ReyalP]

Seriously though, if it's only use is debugging, I can't imagine why anyone would want to change it unless they were being devious - even if those devious intentions were misguided and pointless.

Or they are just misguided.

There will always be ways to lag on demand.