Lag

Even with today's fast network technology, data transfer is not instantaneous. Any action in a game - for example, firing a weapon or moving in an online shooter - can typically take from 10 to 100 milliseconds or even more before the server receives the command. The reactions of other players are registered equally late, which can lead to an apparent doubling of the latency. Game developers try to minimize the effects of network latency with methods such as interpolating or extrapolating other players' movement. These methods have evolved substantially since the early days of Doom and Quake deathmatch, but cries of "LAAAAG" are still heard daily.

Packet loss is also associated with lag. A bad connection can drop network packets, which leads to sudden warping and other strange effects. There isn't really any good solution to network latency and packet loss, except for living in a well-connected area with a good service provider and using reliable equipment.

HDTV lag (input lag)

A more recent but equally frustrating phenomenon is the upscaling lag introduced by new high-definition television sets. The resolution of the video signal from non-HD game consoles, such as the Playstation 2, is usually 720x480 (NTSC) or 720x576 (PAL) interlaced. When connected to a high-definition TV, the TV must upconvert the signal to the native resolution of the display, typically 1920x1080p (progressive) for full HD. Deinterlacing and scaling the signal can lead to a delay of up to a few frames before the image is actually displayed. Note that this delay has nothing to do with the LCD response time shown in technical specifications; the response time only affects ghosting, or motion blur.

HD-capable consoles don't usually suffer from large amounts of lag as there is no need to upconvert the signal. Post-processing and image-enhancing effects in the TV can still delay the picture for a short period, and the "game mode" (see below) should be used when available.

Upscaling the signal can be done quickly, but TV manufacturers haven't so far considered this a big problem and prefer cutting costs by using cheaper components. While the upscaling lag doesn't usually affect the casual gamer, it can completely ruin the gameplay in some timing-intensive genres such as music or fighting games. Experienced Beatmania and Guitar Hero players are particularly prone to this. In-game calibration can help, but the effect of notes registering late on the screen is still enough to throw the player off.

Possible solutions: