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87 lines
4.2 KiB
Markdown
87 lines
4.2 KiB
Markdown
---
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title: SSIM plugin
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short_description: GstValidate plugin to detect frame corruptions
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...
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# SSIM plugin
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GstValidate plugin to run the ssim algorithm on the buffers flowing in the
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pipeline to find regressions and detect frame corruptions.
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It allows you to generate image files from the buffers flowing in the pipeline
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(either as raw in the many formats supported by GStreamer or as png) and then
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check them against pre generated, reference images.
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The ssim algorithm will set a value of 1.0 when images are perfectly identical,
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and -1.0 if they have nothing in common. By default we consider images as similar
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if they have at least a ssim value of 0.95 but you can override it defining the value
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under which the test will be considered as failed.
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Errors are reported on the GstValidate reporting system. You can also ask
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the plugin to generate grey scale output images. Those will be named in a way
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that should lets you precisely see where and how the test failed.
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# Configuration
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The configuration of the plugin is done through a validate configuration file,
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specified with the %GST_VALIDATE_CONFIG environment variable. Each line starting
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with 'ssim,' will configure the ssim plugin. In practice each configuration statement
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will lead to the creation of a #GstValidateOverride object which will then dump
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image files and if wanted compare those with a set of reference images.
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The following parameters can be passed in the configuration file:
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- element-classification: The target element classification as define in
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gst_element_class_set_metadata
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- output-dir: The directory in which the image files will be saved
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- min-avg-priority: (default 0.95): The minimum average similarity
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under which we consider the test as failing
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- min-lowest-priority: (default 1): The minimum 'lowest' similarity
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under which we consider the test as failing
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- reference-images-dir: Define the directory in which the files to be
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compared can be found
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- result-output-dir: The folder in which to store resulting grey scale
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images when the test failed. In that folder you will find images
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with the structural difference between the expected result and the actual
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result.
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- output-video-format: The format in which you want the images to be saved
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- reference-video-format: The format in which the reference images are stored
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- check-recurrence: The recurrence in seconds (as float) the frames should
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be dumped and checked.By default it is GST_CLOCK_TIME_NONE, meaning each
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and every frame is checked. Not that in any case, after a discontinuity
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in the stream (after a seek or a change in the video format for example)
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a check is done. And if recurrence == 0, images will be checked only after
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such discontinuity
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- is-config: Property letting the plugin know that the config line is exclusively
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used to configure the following configuration expressions. In practice this
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means that it will change the default values for the other configuration
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expressions.
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- framerate: (GstFraction): The framerate to use to compute frame number from
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timestamp, allowing to compare frames by 'frame number' instead of trying to
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match timestamp between reference images and output images.
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# Example #
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Let's take a special configuration where we want to compare frames that are
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outputted by a video decoder with the ones after a agingtv element we would
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call my_agingtv. We force to check one frame every 5.0 seconds only (with
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check-recurrence=5.0) so the test is fast.
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The configuration file:
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``` shell
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core, action=set-property, target-element-klass=Sink, property-name=sync, property-value=false
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validatessim, is-config=true, output-video-format="I420", reference-video-format="I420"
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validatessim, element-classification="Video/Decoder", output-dir=/tmp/test/before-agingtv/
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validatessim, element-name=my_agingtv, output-dir=/tmp/test/after-agingtv/, \
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reference-images-dir=/tmp/test/before-agingtv/, \
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result-output-dir=/tmp/test/failures, check-recurrence=5.0
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```
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Save that content in a file called check_agingtv_ssim.config
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## Launch the pipeline
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``` shell
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GST_VALIDATE_CONFIG=check_agingtv_ssim.config gst-validate-1.0-debug uridecodebin uri=file://a/file ! videoconvert ! agingtv name=my_agingtv ! videoconvert ! autovideosink
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```
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