10 classes are annotated with MediaSource

AudioFile in core/modules/media/src/Plugin/media/Source/AudioFile.php
Media source wrapping around an audio file.
File in core/modules/media/src/Plugin/media/Source/File.php
File entity media source.
Image in core/modules/media/src/Plugin/media/Source/Image.php
Image entity media source.
OEmbed in core/modules/media/src/Plugin/media/Source/OEmbed.php
Provides a media source plugin for oEmbed resources.
Test in core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/Test.php
Provides test media source.
TestDifferentDisplays in core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/TestDifferentDisplays.php
Provides test media source.
TestTranslation in core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/TestTranslation.php
Provides test media source.
TestWithConstraints in core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/TestWithConstraints.php
Provides generic media type.
TestWithHiddenSourceField in core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/TestWithHiddenSourceField.php
Provides test media source.
VideoFile in core/modules/media/src/Plugin/media/Source/VideoFile.php
Media source wrapping around a video file.

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