GstValidate Command line tools 1 GstValidate
GstValidate command line tools Documentation of the various command line tools provided by GstValidate

## Introduction

In order to make gst-validate usage simple, dedicated tools that allow plugin developers test there elements in many use cases from a high level perspective are provided with GstValidate.

      gst-validate: The simplest gst-launch like pipeline launcher running inside GstValidate monitoring infrastructure
      gst-validate-transcoding: A tool to easily create media files transcoding pipeline running inside GstValidate monitoring infrastructure
          * Encoding Profile: The serialization format of a GstEncodingProfile
      gst-validate-media-check: A tool to easily check that the discovering of a media file works properly over runs
      gst-validate-launcher: An application permitting to create testsuites on top of GstValidate tools
          * The default testsuite The default GstValidate testsuite
          * Implementing a testsuite How to implement a testsuite

## gst-validate-&GST_API_VERSION;

It is the simplest tool and is used to run a gst launch style pipeline. Monitors are added to it to identify issues in the used elements. At the end a report will be printed, this report will contain information about all issues that were encountered while running gst-validate. To view issues as they are created, set the environment variable GST_DEBUG=validate:2 and it will be printed as gstreamer debugging. You can basically run any GstPipeline pipeline using it. If you are not familiar with gst-launch syntax, please refer to gst-launch's documentation.

Simple playback pipeline:

    gst-validate-1.0 playbin uri=file:///path/to/some/media/file

Transcoding pipeline:

    gst-validate-1.0 filesrc location=/media/file/location ! qtdemux name=d ! queue ! x264enc ! h264parse !  mpegtsmux name=m ! progressreport ! filesink location=/root/test.ts d. ! queue ! faac ! m.

It will report what issues happened during the execution of that pipeline in a human readable report like:

              issue : buffer is out of the segment range Detected on theoradec0.srcpad at 0:00:00.096556426

              Details : buffer is out of segment and shouldn't be pushed. Timestamp: 0:00:25.000 - duration: 0:00:00.040 Range: 0:00:00.000 - 0:00:04.520
              Description : buffer being pushed is out of the current segment's start-stop  range. Meaning it is going to be discarded downstream without any use

The return code of the process will be 18 in case a CRITICAL issue has been found

## The gst-validate-transcoding tool

A command line tool allowing to test media files transcoding with a straight forward syntax. You can for example transcode any media file to vorbis vp8 in webm doing:

    gst-validate-transcoding-&GST_API_VERSION; file:///./file.ogg file:///.../transcoded.webm -o 'video/webm:video/x-vp8:audio/x-vorbis'

It will report what issues happened during the execution of that pipeline in a human readable report like:

              issue : buffer is out of the segment range Detected on theoradec0.srcpad at 0:00:00.096556426

              Details : buffer is out of segment and shouldn't be pushed. Timestamp: 0:00:25.000 - duration: 0:00:00.040 Range: 0:00:00.000 - 0:00:04.520
              Description : buffer being pushed is out of the current segment's start-stop  range. Meaning it is going to be discarded downstream without any use

The return code of the process will be 18 in case a CRITICAL issue has been found

### The Encoding profile serialization format

Internally the transcoding application uses GstEncodeBin. gst-validate-transcoding-&GST_API_VERSION; uses its own serialization format to describe the GstEncodeBin.profile property of the encodebin.

The simplest serialized profile looks like:

    muxer_source_caps:videoencoder_source_caps:audioencoder_source_caps

For example to encode a stream into a webm container, with a ogg audio stream and a h264 video stream, the serialized GstEncodingProfile will look like:

    video/webm:video/x-vp8:audio/x-vorbis

You can also set the preset name of the encoding profile using the caps+preset_name syntax such as in:

    video/webm:video/x-vp8+youtube-preset:audio/x-vorbis

Moreover, you can set the presence property of an encoding profile using the '|presence' syntax such as in:

    video/webm:video/x-vp8|1:audio/x-vorbis

This field allows you to specify how many times maximum a GstEncodingProfile can be used inside a encodebin.

You can also use the 'restriction_caps->encoded_format_caps' to specify the restriction caps to be set on a GstEncodingProfile. It corresponds to the restriction GstCaps to apply before the encoder that will be used in the profile. The fields present in restriction caps are properties of the raw stream (that is before encoding), such as height and width for video and depth and sampling rate for audio. This property does not make sense for muxers.

To force to encode a video in full HD (using webm as a container, vp8 as a video codec and vorbis as an audio codec), you should use:

    video/webm:video/x-raw-yuv,width=1920,height=1080-->video/x-vp8:audio/x-vorbis

#### Some serialized encoding formats examples:

MP3 audio and H264 in MP4:

    video/quicktime,variant=iso:video/x-h264:audio/mpeg,mpegversion=1,layer=3

Vorbis and theora in OGG:

    application/ogg:video/x-theora:audio/x-vorbis

AC3 and H264 in MPEG-TS:

    video/mpegts:video/x-h264:audio/x-ac3

## The gst-validate-media-check tool

A command line tool checking that media files discovering works properly with gst-discoverer. Basically it needs a reference text file containing valid information about a media file (which can be generated with the same tool) and then it will be able to check that those information correspond to what is reported by gst-discoverer over new runs. For example, given that we have a valid reference.media_info file, we can run:

    gst-validate-media-check-&GST_API_VERSION; file:///./file.ogv --expected-results reference.media_info

That will then output found errors if any and return an exist code different from 0 if an error was found.

As you can notice, those tools let us test static pipelines execution and not that the pipeline reacts properly during execution of actions from the end user such as seeking, or changing the pipeline state, etc… In order to make that possible and easy to use we introduced the concept of scenarios

## gst-validate-launcher

To be able to implement actual testsuite based on the previously described command line tools, a test launcher has been developed: gst-validate-launcher.

You can find detailed information about the launcher reading its help manual:

    gst-validate-launcher --help

### Run the GstValidate default testsuite

GstValidate comes with a default testsuite to be executed on a default set of media samples. Those media samples are stored with git-annex so you will need it to be able to launch that default testsuite.

The first time you launch the testsuite, you will need to make sure that the media samples are downloaded. To do so and launch the testsuite you can simply do:

    gst-validate-launch validate --sync

This will only launch the GstValidate tests and not other application that might be supported (currently ges-launch is also supported and has its own default testsuite).

Launching the default testsuite will open/close many windows, you might want to mute it so you can keep using your computer:

    gst-validate-launch validate --sync --mute

### Example of a testsuite implementation

To implement a testsuite, you will have to write some simple python code that will define the test to be launched by the gst-validate-launcher.

In that example, we will consider that you want to write a whole new testsuite based on your own media samples and scenarios. That set of file and the testsuite implementation file will be structured as follow:

    testsuite_folder/
      |-> testsuite.py
      |-> sample_files/
          |-> file.mp4
          |-> file1.mkv
          |-> file2.ogv
      |-> scenarios
          |-> scenario.scenario
          |-> scenario1.scenario

You should generate the .media_infos files. To generate them for local files, you can use:

    gst-validate-launch --medias-paths /path/to/sample_files/ --generate-media-info

For remote streams, you should use gst-validate-media-check-&GST_API_VERSION;. For an http stream you can for example do:

    gst-validate-media-check-&GST_API_VERSION; http://someonlinestream.com/thestream --output-file /path/to/testsuite_folder/sample_files/thestream.stream_info

The gst-validate-launcher will use those .media_info and .stream_info files to generate the tests as those contain the necessary information.

Then you will need to write the testsuite.py file. You can for example implement the following testsuite:

    import os

    # Make sure gst-validate-launcher uses our special media files
    options.paths = os.path.dirname(os.path.realpath(__file__))

    # Make sure GstValidate will be able to use our special scenarios
    # from the testsuite_folder/scenarios folder
    os.environ["GST_VALIDATE_SCENARIOS_PATH"] = \
        os.path.join(os.path.dirname(os.path.realpath(__file__)), "scenarios")

    # You can activate the following if you care only about the critical issues in
    # the report:
    # os.environ["GST_VALIDATE"] = "print_criticals"

    # Make gst-validate use our scenarios
    validate.add_scenarios(["scenario", "scenario1"])

    # Now add the theora and vorbis in OGG as a wanted transcoding format. That means
    # that tests with all the media files/streams will be converted to that format.
    validate.add_encoding_formats([MediaFormatCombination("ogg", "vorbis", "theora")])

    # Use the GstValidatePlaybinTestsGenerator to generate tests that will use playbin
    # and GstValidateTranscodingTestsGenerator to create media transcoding tests that
    # will use all the media format added with validate.add_encoding_formats
    validate.add_generators([validate.GstValidatePlaybinTestsGenerator(validate),
                             GstValidateTranscodingTestsGenerator(self)])

    # Blacklist some test that are known to fail because a feature is not supported
    # or any reason.
    # The tuple defining those tests is of the form:
    # ("regex defining the test name", "Reason why the test should be disabled")
    validate.set_default_blacklist([
            ("validate.*.scenario1.*ogv$"
             "oggdemux does not support some action executed in scenario1")]
            )

Once this is done, we got a testsuite that will:

- Run playbin pipelines on file.mp4, file1.mkv and file2.ogv executing "scenario" and "scenario1" scenarios
- Transcode file.mp4, file1.mkv and file2.ogv to theora and vorbis in OGG

The only thing to do to run the testsuite is:

    gst-validate-launcher --config /path/to/testsuite_folder/testsuite.py