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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.
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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 description
"config" action 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:
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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:
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description, 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:
Action type examples:
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:
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gst-validate-1.0 --inspect-action-type |
and to include transcoding specific action types:
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gst-validate-transcoding-1.0 --inspect-action-type |
Many scenarios are distributed with gst-validate, you can list them all using:
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gst-validate-1.0 --list-scenarios |
You can find more information about the scenario implementation and action types in the GstValidateScenario section.