Scenarios

# GstValidate Scenario File Format

To be able to define a list of actions to execute on a `GstPipeline`, a dedicated file format is used. The name of the scenario is the name of the file without its `.scenario` extension. The scenario file format is based on the `GstStructure` serialized format which is a basic, type aware, key value format. It takes the type of the action in the first comma separated field, and then some key value pairs in the form `parameter=value` separated by commas. The values type will be guessed if not casted as in `parameter=(string)value`. You can force the type guessing system to actually know what type you want by giving it the right hints. For example to make sure the value is a double, you should add a decimal (ie. `1` will be considered as a `int`, but `1.0` will be considered as a `double` and `"1.0"` will be considered as a `string`).

For example to represent a seek action, you should add the following line in the `.scenario` file.

    seek, playback-time=10.0, start=0.0, flags=accurate+flush

The files to be used as scenario should have a `.scenario` extension and should be placed either in `$USER_DATA_DIR/gstreamer-1.0/validate/scenarios` , `$GST_DATADIR/gstreamer-1.0/validate/scenarios` or in a path defined in the $GST_VALIDATE_SCENARIOS_PATH environment variable.

Each line in the `.scenario` file represent an action (you can also use `\` at the end of a line write a single action on multiple lines). Usually you should start you scenario with a `meta` structure in order for the user to have more information about the scenario. It can contain a `summary` field which is a string explaining what the scenario does and then several info fields about the scenario. You can find more info about it running:

    gst-validate-1.0 --inspect-action-type action_type_name

So a basic scenario file that will seek three times and stop would look like:

    meta, summary="Seeks at 1.0 to 2.0 then at \
    3.0 to 0.0 and then seeks at \
    1.0 to 2.0 for 1.0 second (between 2.0 and 3.0).", \
    seek=true, duration=5.0, min-media-duration=4.0
    seek, playback-time=1.0, rate=1.0, start=2.0, flags=accurate+flush
    seek, playback-time=3.0, rate=1.0, start=0.0, flags=accurate+flush
    seek, playback-time=1.0, rate=1.0, start=2.0, stop=3.0, flags=accurate+flush

Many action types have been implemented to help users define their own scenarios. For example there are:

- `seek`: Seeks into the stream.
- `play`: Set the pipeline state to `GST_STATE_PLAYING`.
- `pause`: Set the pipeline state to `GST_STATE_PAUSED`.
- `stop`: Stop the execution of the pipeline.

> NOTE: This action actually posts a `GST_MESSAGE_REQUEST_STATE` message requesting `GST_STATE_NULL` on the bus and the application should quit.

To get all the details about the registered action types, you can list them all with:

    gst-validate-1.0 --inspect-action-type

and to include transcoding specific action types:

    gst-validate-transcoding-1.0 --inspect-action-type

Many scenarios are distributed with `gst-validate`, you can list them all using:

    gst-validate-1.0 --list-scenarios

You can find more information about the scenario implementation and action types in the `GstValidateScenario` section.

## Default variables

Any action can use the default variables:

- `$(position)`: The current position in the pipeline as reported by gst_element_query_position()
- `$(duration)`: The current duration of the pipeline as reported by gst_element_query_duration()
- `$(TMPDIR)`: The default temporary directory as returned by `g_get_tmp_dir`.
- `$(SCENARIO_PATH)`: The path of the running scenario.
- `$(SCENARIO_DIR)`: The directory the running scenario is in.
- `$(SCENARIO_NAME)`: The name the running scenario

It is also possible to set variables in scenario with the `set-vars` action.

The results of the search are