I think there is some confusion around what people are referring to as lag; There is the lag that everyone knows, where cars will zip and zoom all over the place which is caused by network issues. I've seen no more of this than I experienced in GT Sport (in fact, probably less!) Then there is "jitter", where cars appear to be rapidly shifting on their local Y axis (left/right). It is my belief that this jitter is neither a network/lag issue or a cross-gen hardware issue, but completely software based and nothing that cannot be fixed:
- For every other frame most data pertaining to your car is packaged up into a Packet[1] and is sent to all other players via the host[2]
- Each packet will contain, amongst many other things, a X (up/down) coordinate, a Y (left/right) coordinate and a Z (forwards/backwards) coordinate.
- Each packet sent is of a fixed size so the recieving device knows if it recieved a complete packet or not.
- If a packet is smaller than the recieving device expects it is discarded, in effect becoming a lost packet.
- A lot of lost packets produce the typical lag we all recognise. However...
- Since jittering vehicles appear to maintain their correct Z coordinate[3] it can be safely assumed that the recieving devices did indeed recieve a complete packet.
- If a device has recieved a complete packet, which is not out of sequence, lag is not the issue.
- If a device is
[1] It will be pretty much the same data that GT was recently "discovered" to ouput last year which is being used for motion control rigs and external dash boards, etc.
[2] Since GT has had online multiplayer rooms those with fixed ownership utilise star type networks and those with unfixed ownership utilise mesh type networks. As GT7 only has fixed room ownership it is probably more than safe to assume all rooms now operate as a star type network.
[3] I tested this today; I was fortunate to find someone in a lobby who was of a very similar pace to me and was jittering. I sat on their rear bumper for lap after lap and not once did we visibly make contact nor did their car do the tell-tale lag induced sudden lurch forward despite appearing not to have made contact.
A further observation is that the Y axis jitter increases with steering input; on straights with no steering input, the jitter stops. If a car on a straight moves to defend a line, requiring only a little steering input, there is only a little amount of jitter until the steering is straightened up again. In corners, depending upon the radius of the corner, the jitter gets worse.
Again, if only one axis affected it
cannot be a network or cross-gen hardware issue. If its not a network or cross-gen hardware issue its got to be a software issue and thus
can be fixed.
