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# 10 Event history

VICE supports recording an arbitrary session on the emulated machine and playing back this session later. This is done by saving a snapshot at the beginning of the recording session and then remembering all the user interaction such as keyboard and joystick input. We call this an 'event history'. The main purpose for having an event history is to create game sessions, e.g. recording how to solve a game. An example walkthrough for the well known game "Fort Apocalypse" is available.

This brief chapter will advise you how to record and playback such a session. Although it is based on the WinVICE x64 release and its user interface, histories may be transferred to other machines and other ports that support event history, e.g. the Unix port.

## 10.1 Recommended Settings

When using the event history feature it is possible that the playback session differs from what was done at recording time. This might arise due to a problem in the initial snapshot or settings. Here are some suggestions to minimize the chance of failures in the session: a. Reset to default settings. b. Choose refresh rate 1/1. c. Choose joystick and Video/Doublesize settings as desired or needed. d. SID engine must be reSID (which is the default). e. Choose Drive settings/Idle method: None Do not change any settings during recording or playback!

## 10.2 Recorded Events

The following is a list of the user interaction that will be recorded: - Joystick movement and button - Keyboard - Resetting the machine (hard and soft) - Attaching or detaching disk/tape images (see 8. Limitations) - Datasette controls

## 10.3 Recording an Event History

Recording an event history will create one or two files for a snapshot and the list of the user events. First, create an empty directory in which these files are to be saved and then select this directory and the name of the snapshot files via 'Snapshot//Select History files/directory'. Next, attach the disk or tape image with the game you want to record and load and run the game.

Start recording via 'Snapshot//Start/Stop Recording History'. Play the game. All actions will be recorded. After the game is finished, stop recording via 'Snapshot//Start/Stop Recording History'. The selected directory should now contain the two snapshot files (default ist start.vsf and end.vsf).

## 10.4 Setting and Returning to Milestones

It is difficult to finish a game in one sitting and noone wants to record all their mistakes and lost lives. Use the milestone feature in a recording session in the following way:

Set a milestone when you have finished a level or completed a task ('Snapshot//Set recording milestone' or ALT-E). This will save the event history and a snapshot of the machine to the file end.vsf but recording will continue.

Return to the last milestone when you have made a mistake or lost a life ('Snapshot//Return to milestone' or ALT-U). This will reset the game and the event history to the last milestone snapshot so that you can try again.

## 10.5 Continuing an Event History

If you have stopped a recording session and want to continue it later, you should create a backup of your start.vsf and end.vsf files first to avoid overwriting them by accident.

Then change the event history start mode: 'Snapshot//Recording start mode//Load existing snapshot'. When you start recording now, you will continue where the session was stopped last time.

Another way of continuing an existing history is to start somewhere inside the history (e.g. you have recorded 10 minutes of a game and later recognize that you made a mistake after 6 minutes that makes it impossible to finish the game). For this you have to select the start mode 'Overwrite playback'. Now you can start the playback with 'Snapshot//Start/Stop Playback History' and when you reach the point where you want to change the history you can directly switch to recording via 'Snapshot//Start/Stop Recording History'.

## 10.6 Playing Back an Event History

To play back an event history, select the directory with the history files start.vsf and end.vsf via 'Snapshot//Select History directory' and start the playback with 'Snapshot//Start/Stop Playback History'. Enjoy! During playback any user interaction is disabled. The playback stops when the end of the session is reached or if 'Snapshot//Select History directory' is selected again.

## 10.7 Limitations and Suggestions

a. Snapshot files will be quite big (>1MB) if a disk image has been attached. If possible, use PRG or T64 images to reduce the size of snapshot files. b. Snapshots may not be 100% accurate even with all the recommended settings.

## 10.8 Event history resources

`EventSnapshotDir`
  String specifying the directory used for loading and saving snapshots.
`EventStartSnapshot`
  String specifying the filename for the start snapshot. ["start.vsf"]
`EventEndSnapshot`
  String specifying the filename for the end snapshot. ["end.vsf"]
`EventStartMode`
  Integer specifying how to start event recording. (0: save new snapshot, 1: load existing snapshot, 2: reset, 3: playback)
`EventImageInclude`
  Boolean specifying whether to include ROM and Disk images in the snapshots. [1]

## 10.9 Event history command-line options

`-playback`
  Playback recorded events

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