gstreamer/docs/plugins/validateflow.md

Validate Flow plugin

Validate Flow plugin — GstValidate plugin to record a log of buffers and events and compare them to an expectation file.

Description

This plugin exists for the purpose of testing non-regular-playback use cases where the test author specifies the full pipeline, a series of actions and needs to check whether the generated buffers and events make sense.

The testing procedure goes like this:

1. The test author writes a validate configuration where validateflow is used. A pad where monitoring will occur is specified. A scenario containing actions to run (e.g. push buffers from an appsrc) can also be specified.

2. The test author runs the test with the desired pipeline, the validate config created before, and the scenario. Since an expectation file does not exist at this point, validateflow will create one. The author should check its contents for any missing or unwanted events. No actual checking is done by validateflow in this step, since there is nothing to compare to yet.

3. Further executions of the test will also record the produced buffers and events, but now they will be compared to the previous log (expectation file). Any difference will be reported as a test failure. The original expectation file is never modified by validateflow. Any desired changes can be made by editing the file manually or deleting it and running the test again.

validateflow can be run standalone with gst-validate-1.0, but most of the time it will be used in pipelines.json, run by gst-validate-launcher, which will take care of creating all the necessary files and some configuration boilerplate. To run all these tests execute:

gst-validate-launcher validate.launch_pipeline.'*' -m

You can also specify a specific test like this:

gst-validate-launcher validate.launch_pipeline.qtdemux_change_edit_list.default -m

Example

The following is an example of a test in pipelines.json using validateflow. This file can usually be found in ~/gst-validate/gst-integration-testsuites/testsuites/pipelines.json:

"qtdemux_change_edit_list":
{
    "pipeline": "appsrc ! qtdemux ! fakesink async=false",
    "config": [
        "%(validateflow)s, pad=fakesink0:sink, record-buffers=false"
    ],
    "scenarios": [
        {
            "name": "default",
            "actions": [
                "description, seek=false, handles-states=false",
                "appsrc-push, target-element-name=appsrc0, file-name=\"%(medias)s/fragments/car-20120827-85.mp4/init.mp4\"",
                "appsrc-push, target-element-name=appsrc0, file-name=\"%(medias)s/fragments/car-20120827-85.mp4/media1.mp4\"",
                "checkpoint, text=\"A moov with a different edit list is now pushed\"",
                "appsrc-push, target-element-name=appsrc0, file-name=\"%(medias)s/fragments/car-20120827-86.mp4/init.mp4\"",
                "appsrc-push, target-element-name=appsrc0, file-name=\"%(medias)s/fragments/car-20120827-86.mp4/media2.mp4\"",
                "stop"
            ]
        }
    ]
},

This example shows the elements of a typical validate flow test (a pipeline, a config and a scenario). Some actions typically used together with validateflow can also be seen. Notice variable interpolation is used to fill absolute paths for media files in the scenario (%(medias)s). In the configuration, %(validateflow)s is expanded to something like this, containing proper paths for expectations and actual results:

validateflow, expectations-dir="/home/ntrrgc/gst-validate/gst-integration-testsuites/flow-expectations/qtdemux_change_edit_list", actual-results-dir="/home/ntrrgc/gst-validate/logs/validate/launch_pipeline/qtdemux_change_edit_list"

When running the tests, a config file will be created under the hood by gst-validate-launcher and passed as GST_VALIDATE_CONFIG. Similarly, scenario files will be created and set in GST_VALIDATE_SCENARIO. gst-validate-1.0 will be run with the specified pipeline.

The resulting log looks like this:

event stream-start: GstEventStreamStart, flags=(GstStreamFlags)GST_STREAM_FLAG_NONE, group-id=(uint)1;
event caps: video/x-h264, stream-format=(string)avc, alignment=(string)au, level=(string)2.1, profile=(string)main, codec_data=(buffer)014d4015ffe10016674d4015d901b1fe4e1000003e90000bb800f162e48001000468eb8f20, width=(int)426, height=(int)240, pixel-aspect-ratio=(fraction)1/1;
event segment: format=TIME, start=0:00:00.000000000, offset=0:00:00.000000000, stop=none, time=0:00:00.000000000, base=0:00:00.000000000, position=0:00:00.000000000
event tag: GstTagList-stream, taglist=(taglist)"taglist\,\ video-codec\=\(string\)\"H.264\\\ /\\\ AVC\"\;";
event tag: GstTagList-global, taglist=(taglist)"taglist\,\ datetime\=\(datetime\)2012-08-27T01:00:50Z\,\ container-format\=\(string\)\"ISO\\\ fMP4\"\;";
event tag: GstTagList-stream, taglist=(taglist)"taglist\,\ video-codec\=\(string\)\"H.264\\\ /\\\ AVC\"\;";
event caps: video/x-h264, stream-format=(string)avc, alignment=(string)au, level=(string)2.1, profile=(string)main, codec_data=(buffer)014d4015ffe10016674d4015d901b1fe4e1000003e90000bb800f162e48001000468eb8f20, width=(int)426, height=(int)240, pixel-aspect-ratio=(fraction)1/1, framerate=(fraction)24000/1001;

CHECKPOINT: A moov with a different edit list is now pushed

event caps: video/x-h264, stream-format=(string)avc, alignment=(string)au, level=(string)3, profile=(string)main, codec_data=(buffer)014d401effe10016674d401ee8805017fcb0800001f480005dc0078b168901000468ebaf20, width=(int)640, height=(int)360, pixel-aspect-ratio=(fraction)1/1;
event segment: format=TIME, start=0:00:00.041711111, offset=0:00:00.000000000, stop=none, time=0:00:00.000000000, base=0:00:00.000000000, position=0:00:00.041711111
event tag: GstTagList-stream, taglist=(taglist)"taglist\,\ video-codec\=\(string\)\"H.264\\\ /\\\ AVC\"\;";
event tag: GstTagList-stream, taglist=(taglist)"taglist\,\ video-codec\=\(string\)\"H.264\\\ /\\\ AVC\"\;";
event caps: video/x-h264, stream-format=(string)avc, alignment=(string)au, level=(string)3, profile=(string)main, codec_data=(buffer)014d401effe10016674d401ee8805017fcb0800001f480005dc0078b168901000468ebaf20, width=(int)640, height=(int)360, pixel-aspect-ratio=(fraction)1/1, framerate=(fraction)24000/1001;

Configuration

In order to use the plugin a validate configuration file must be provided, containing a line starting by validateflow followed by a number of settings. Every validateflow line creates a ValidateFlowOverride, which listens to a given pad. A test may have several validateflow lines, therefore having several overrides and listening to different pads with different settings.

• pad: Required. Name of the pad that will be monitored.
• record-buffers: Default: false. Whether buffers will be logged. By default only events are logged.
• buffers-checksum: Default: false. Whether a checkum of the buffer data is logged. Implies record-buffers.
• ignored-event-fields: Default: "stream-start={ stream-id }" (as they are often non reproducible). Key with a serialized GstValueList(str) of fields to not record.
• ignored-event-types: Default: { }. List of event type names to not record
• logged-event-types: Default: NULL. List of event type names to not record, if noone provided, all events are logged, except the ones defined in the ignored-event-types.
• expectations-dir: Path to the directory where the expectations will be written if they don't exist, relative to the current working directory. By default the current working directory is used, but this setting is usually set automatically as part of the %(validateflow)s expansion to a correct path like ~/gst-validate/gst-integration-testsuites/flow-expectations/<test name>.
• actual-results-dir: Path to the directory where the events will be recorded. The expectation file will be compared to this. By default the current working directory is used, but this setting is usually set automatically as part of the %(validateflow)s expansion to the test log directory, i.e. ~/gst-validate/logs/validate/launch_pipeline/<test name>.

Scenario actions

Scenarios with validateflow work in the same way as other tests. Often validatetests will use appsrc in order to control the flow of data precisely, possibly interleaving events in between. The following is a list of useful actions.

• appsrc-push: Pushes a buffer from an appsrc element and waits for the chain operation to finish. A path to a file is provided, optionally with an offset and/or size.
• appsrc-eos: Queues an EOS event from the appsrc. The action finishes immediately at this point.
• stop: Tears down the pipeline and stops the test.
• checkpoint: Records a "checkpoint" message in all validateflow overrides, with an optional explanation message. This is useful to check certain events or buffers are sent at a specific moment in the scenario, and can also help to the comprehension of the scenario.

More details on these actions can be queried from the command line, like this:

gst-validate-1.0 --inspect-action-type appsrc-push