Instant Replay

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Instant Replay is a fun feature that is found under "View" in the menubar.

FG 2.4.0 and earlier

The instant replay dialog for FG2.4.0 and earlier.

For FG 2.4.0 and earlier, a simple dialog box is presented with a couple of options (duration of replay and view type).

  • A value of 0 for duration will replay the entire flight. The default value is 90 seconds (similar to MSFS). If you want something different, just type the number of seconds desired in the text box.
  • The view option is a drop-down box with three options corresponding to Cockpit, Chase and Tower views. No matter what this is initially set to, the view type can be changed as normal with v/V and ctrl-v to cycle forwards or backwards through all the available views or return to default Cockpit view.

To return to normal flight, press 'p' twice (pause/unpause). This returns you to the point where you selected Instant Replay. You cannot back up 30 seconds or so and try that landing again. Also, it is currently not possible to save the replay buffer to a file to load and replay a flight later on.

Note: only data directly related to your aircraft is saved and played back, AI objects, multiplayer aircraft or any random features will not be replayed.

FG 2.6.0 and later

Ambox move.png
It has been suggested that this article be moved to Flight Recorder.

the flight recorder tapes are only 1 or 2 hours max... at one time i wanted to do one for a cross-country flight but when i saved it i only got the last hour or two

Cquote1.png the "my controls" button is currently intentionally disabled for JSBSim and for YASim helicopters. Only works with YASim aircraft so far.

FG 2.6.0 introduced a new replay system which can be adapted to individual aircraft and provides better recordings/playbacks. It also introduces a new GUI as well as a dedicated file format for serializing flights to disk: Fgtape.

The instant replay dialog.

Cquote1.png The replay system uses three buffer levels: short term memory records 60

seconds at full frame rate, mid term buffer records another 10 minutes
at 2fps, and the long term buffer holds 1 hour at 1/5fps. As I stated
earlier, I'm not changing the buffering scheme itself. However, the
buffer durations and rates are exposed by properties now. So, if you had
enough memory, you could increase the buffer sizes or change their rates.

Cquote1.png You should be able to extend the recording limit by changing the /sim/reply/duration property (e.g. by clicking on View -> Instant Replay and changing the duration in the textbox next to the "Loop" checkbox).
— Alessandro Menti (Feb 20th, 2016). Re: [Flightgear-devel] flight recorder time limit.
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Starting and Controlling Replay

  • Press Ctrl-r or select Instant Replay from the View menu to start the replay. Replay starts immediately.
  • Press p or click pause to pause/resume the replay.
  • Use the left/right arrow keys, or the <<, >> buttons to skip. You can also use the mouse and drag the time slider.
  • Use the up/down arrow keys, or the +, - buttons to change replay speed. You can replay at slow-motion, real-time or fast-forward speed.
  • Enable the Loop checkbox to continuously repeat the playback. When you configure a duration (in seconds) then only the last few seconds are continuously replayed.

Stopping Replay

  • Press Escape or the End Replay button to stop replay and return to the position prior to starting replay.
  • Alternatively, click the My Controls! button to take over control at any point. With this feature you can use the replay system to go back in time, regain control and then continue the flight from a past position. This is useful to train particular flight phases, such as flying the same approach again and again, maybe using different weather/wind conditions.

Feature Requests

Cquote1.png If the F/R data was written to disk immediately, so it doesn't have to take up valueable RAM, would make it possible to record nearly indefinitely (depending on disk space). And delete this data like a tmp-file on shutdown, if it isn't stored somewhere else...
— chris (Feb 20th, 2016). [Flightgear-devel] flight recorder time limit.
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Cquote1.png This should be quite doable, the FlightRecorder code is quite self-contained. Also it uses thining of the history buckets so actually I think for multi-hour data, maybe it just needs a coarser (maybe one sample per 5 seconds?) bucket of larger sie. If you want to look at the code I’m happy provide guidance on enhancing it.
— James Turner (Feb 21st, 2016). Re: [Flightgear-devel] flight recorder time limit.
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[Something similar to this is on next - see below.]

FG next as of 2020-9

There are various improvements to record/replay on next, including: record/replay of multiplayer aircraft; continuous recording to file without any loss of detail; periodic generation of a recovery snapshot, allowing resumption after a flightgear crash.

For details, see:

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